NOTES / SOLVED QUESTION/ANSWERS:GENERAL SCIENCE-8(PTB) PUNJAB CURRICULUM& TEXTBOOK BOARD LAHORE 2015 (NEW)

It's only fair to share...Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInPrint this pageEmail this to someone
image_pdf

NOTES / SOLVED QUESTION/ANSWERS:GENERAL SCIENCE-8(PTB) PUNJAB CURRICULUM& TEXTBOOK BOARD LAHORE 2015 (NEW)

CONTENTS

  1. Human Organ Systems—————————— 1
  2. Cell Division——————————————–19
  3. Biotechnology—————————————–32
  4. Pollutants and Their Effects on Environment 45
  5. Chemical Reactions———————————-61
  6. Acids, Bases/Alkalis and Salts ——————–78
  7. Force and Pressure ———————————99
  8. Measurement of Physical Quantities———113
  9. Sources and Effects of Heat Energy ———-123
  10. Lenses —————————————–137
  11. Electricity in Action ————————149
  12. Exploring Space —————————–160

 

CH: 1 HUMAN ORGAN SYSTEMS P:1-18

QUESTIONS

1.1 ENCIRCLE THE CORRECT OPTION.

(i) The neurons which decide about the action for a certain stimulus:

  1. sensory neuron b. motor neuron c. interneuron d. all of these

(ii) The parts of a neuron which receive messages are:

  1. cell bodies b. dendrites c. axons d. nuclei

(iii) Heartbeat is controlled by:

  1. cerebrum b. cerebellum c. medulla oblongata d. hypothalamus

 (iv) Many axons present side by side and enclosed in a common sheath:

  1. nerve cell b. nerve c. dendrite d. spinal cord

(v) Sensory neurons carry messages towards:

  1. muscles b. muscles and glands c. sense organs d. brain and spinal cord

(vi) If body movements are NOT precise and accurate, the part of brain which may be affected:

  1. cerebellum b. cerebrum c. thalamus d. midbrain

(vii) When you have a toothache, you feel pain because:

  1. there is a cavity in your tooth
  2. tiny bits of food are left between your teeth c. bacteria digest the food left between your teeth and produce an acid
  3. the cavity reaches the nerves and the nerves send a message to the brain

(viii) The part of body which filters wastes from blood:

  1. liver b. kidney c. intestine d. stomach

(ix) The part of the nephron where reabsorption of useful materials occurs from filtrate to blood; 

  1. glomerulus b. renal tubule c. collecting duct d. Bowman’s capsule

(x) The function of nephron is to: 

  1. store urine b. form urine c. push out urine from urinary bladder d. break stones in kidneys

ANSWERS: (i-b) (ii-b)(iii-c)(iv-b) (v-d) (vi-a) (vii-d) (viii-b) (ix-a) (x-b)

1.2 WRITE NAMES OF THE MAIN PARTS OF THE FOLLOWING.

(i) forebrain (ii) Hindbrain  (iii) Neuron (iv) Nephron

Ans:

Forebrain Hindbrain Neuron Nephron
Cerebrum Cerebellum Dendrites Bowman Capsule
Thalamus Pons Axon Glomerulus
Hypothalamus Medulla oblongata Nucleus, Cell body Loop of Henle

 

1.3 WRITE THE FUNCTIONS OFTHE FOLLOWING.

(i) Forebrain (ii) Hindbrain (iii) Neuron (iv) nephron

Ans:

(i) FOREBRAIN

Cerebrum controls thinking, feeling, emotions, seeing -hearing, perception, memory speech decision making.

Thalamus controls sensory functions.

Hypothalamus controls hunger, thirst and body temperature

(ii) HINDBRAIN

Cerebellum maintains body balance, and position.

Pens controls sleep, swallowing, equilibrium and taste.

Medulla oblongata controls heartbeat, breathing and digestion.

  1. i) NEURONS

Carry message in the form of electrochemical Waves called nerve impulse.

(iv) NEPHRON

Nephron filters blood, separates waste from urine.

 

1.4 GIVE SHORT ANSWERS.

(i) Give at least three examples of voluntary actions.

Answer: Reading walking, running

(ii) Give at least three examples of involuntary actions.

Answer: Breathing, blood, circulation, absorption of food.

(iii) Define: (a) sensory neurons (b) motor neuron (C) inter-neuron

Answer: (a) Sensory neurons

Carry nerve impulse from sensory organs (ear, nose, tongue, eye, skin) to the brain.

(b) Motor neuron: it Carry nerve impulse from CNS to effectors.

(c) Inter-neuron

They form a -link between sensory and motor neurons.

(iv) Skin is also considered as excretory organ. Why?

Answer: Skin is an excretory organ because it allows wastes to come on the outer” surface of skin‘ and they are eliminated during perspiration (sweating)

 

1.5 DIFFERENTIATE BETWEEN:

(i) Receptors and effectors

Answer: RECEPTORS sense organ to brain. Receptors connected with sensory neurons. They send message from Neuron and nerve.

 EFFECTORS

Effectors are the muscles and glands. The parts which respond by the action of motor neuron bring message from the brain.

(ii) Neuron and nerve

Answer: NEURON

Neuron are the nerve cell V which are of different types’: sensory, inter; motor, They are the brain cells.

Nerve

Nerve is the signal or message which is conducted by different types ‘0f neurons from brain to sense organ or sense organ to brain.

(iii) Voluntary actions and involuntary actions

Answer: VOLUNTARY ACTIONS

The actions which are controlled by our Will, e.g walking, reading. ’

 INVOLUNTARY ACTIONS

The actions which are not under our control. Such as breathing digestion; heart beat.

(iv) Kidneys and lungs

Answer: KIDNEYS

Kidneys are the structures which separate Wastes material from blood and make it urine and expels from the body.

LUNGS

Lungs are the structures which are responsible for breathing. They expel Waste CO2 out side the body and inhale fresh O2 inside the body.

(v) Lithotripsy and dialysis

Answer: LITHOTRIPSY

Lithotripsy is the process in which stones are removed by an artificial method.  It is the bombardment of shockwaves on the stones from outside.

These waves break the stones.

DIALYSIS

Cleaning of blood by artificial methods is called dialysis. It is done by the machine called dialyzer.

 

 

1.6 EXPLAIN THE CENTRAL NERVOUS SYSTEM.
Ans. Central nervous system acts as a control centre of the whole nervous system. It comprises brain and spinal cord.

BRAIN

Human brain is enclosed in a bony skull called cranium. It consists of billions of inter-neurons and is divided into the following parts.

1. FOREBRAIN

Forebrain is the largest part of the brain. It consists of three main parts, i.e. cerebrum, thalamus and hypothalamus.

CEREBRUM

Cerebrum is the topmost and the largest part of the brain. It is divided into right and left cerebral hemispheres.

FUNCTIONS

Cerebrum controls many actions like thinking, feelings, emotions, seeing, hearing, perceptions, memory, speech, decision making, etc.

THALAMUS

Inside cerebrum there is small structure called thalamus.

FUNCTIONS

It controls many sensory functions. Hypothalamus lies at the base of thalamus. It controls body temperature, hunger and thirst.

 

2. MIDBRAIN

Midbrain is a small part of the brain which is present below the cerebrum.

FUNCTIONS

It receives information from sense organs and sends message to appropriate part of the forebrain.

3. HINDBRAIN

A Hindbrain consists of three parts i.e. cerebellum, pons and medulla oblongata.

CEREBRUM

Cerebellum lies under the back part of the cerebrum.

FUNCTIONS

It acts as a controller for maintaining the body balance and making precise and accurate movements.

PONS

Pons is an oval structure present beneath the midbrain.

Human Organ System

FUNCTIONS

It controls many functions like sleep, swallowing, equilibrium, and taste, etc.

MEDULLA OBLONGATA

Medulla oblongata forms the posterior part of the brain Where it is connected with the spinal cord.

FUNCTIONS

Medulla oblongata controls heartbeat, breathing and digestion etc. Medulla, oblongata also keeps on working when the rest of the brain goes to sleep.

1.7 DESCRIBE PERIPHERAL NERVOUS SYSTEM.
S system (PNS)

Peripheral nervous system (PN S) consists of a network of nerves which are spread in the body to connect all ;the body parts to the central nervous system (brain & spinal cord). The nerves which arise from brain are called cranial nerves. The nerves which arise from spinal cord are called spinal nerves. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves in human body.

1.8 DESCRIBE THE MAIN PARTS OF EXCRETORY SYSTEM IN MAN.
ANS. KIDNEYS & ASSOCIATED STRUCTURES

1. KIDNEYS

Human body has two dark brown, bean-shaped kidneys in the

abdominal region, one on either side of the vertebral column. The right

kidney is a little lower than the left

one. The outer surface of kidney is

convex while, the inner surface is

concave. The following structures are Left

attached with kidneys.

2 . URETERS  URETER

A tube which arises from each

kidney and enters in urinary bladder

is called ureter. It transports urine

from kidneys to urinary bladder. Human excretory system

3. URINARY BLADDER

A Urinary bladder is a muscular sac which collects urine from both ureters.

4.URETHRA

A fine tube through which urine is released from urinary bladder to the outside is called Urethra.

1.9 WRITE A NOTE ON THE INTERNAL STRUCTURE OF KIDNEY.
ANS. INTERNAL STRUCTURE OF KIDNEY

             Internally each kidney is divided into three regions, i.e. renal cortex,

renal medulla and

renal pelvis.

Renal cortex is the outermost region. Renal medulla is the. middle region which is divided into conical masses called renal pyramids. Renal pelvis is the inner area where urine is drained. The urine from renal pelvis moves into ureter.

1.10 DESCRIBE STRUCTURE OF NEPHRON.
Ans. NEPHRON

Nephrons are the functional units of the kidneys. They are the

tubules where urine is formed. There are over one million nephrons in

each kidney. Each nephron has two parts, i.e;

renal corpuscle and

renal tubule.

RENAL CORPUSCLE

It is the first part of nephron. It consists of two structures, i.e.,

glomerulus and Bowman’s capsule. Glomerulus is a tuft of blood

capillaries formed by the division of small arteries. Bowman’s

capsule is a cup-shaped structure enclosing glomerulus.

RENAL TUBULE

This part of nephron starts after Bowman’s capsule. The first

coiled part of renal tubule is called proximal tubule. The next part is

U-shaped and is called Loop of Henle. The last part of the renal

tubule is again coiled and is called distal tubule.

The distal tubules of many nephrons open in a collecting duct.

Many collecting ducts join and drain into renal pelvis.

1.11 WRITE NOTES ON:

a) Reflex action b) Renal failure c) Dialyzer

ANSWER: REFLEX ACTION

An immediate and involuntary response to a stimulus is called

reflex action. Quick pulling of hand just after touching the hot object is

a common example of reflex action.

In this example of reflex action, temperature of hot object is a

stimulus which is received by the cells (receptors) of the skin. A nerve

impulse is created in the sensory neuron present in skin. The nerve

impulse is carried by the sensory neuron to the spinal cord. The inter

neuron of the spinal cord transmits the impulse to the motor neuron.

The motor neuron carries the impulse to the arm muscles (effectors).

The arm muscles contract and pull the hand back. The pathway of

nerve impulses which complete a reflex action is called reflex arc. It

consists of receptor, a sensory neuron, an inter neuron, a motor neuron

and effectors.

        B) RENAL FAILURE

Renal failure is the complete or partial failure of kidneys to Work.

The main causes of renal failure are long-term infections, diabetes.

mellitus and hypertension, Diabetes mellitus is a disease in which

sugar level increases in the blood. Hypertension is -a state of high blood

pressure  the body. Sudden blockage of blood supply to the kidneys

may also result in renal failure. Dialysis and kidney transplant are the

treatments of renal failure.

 

Ans. DIALYSIS

Cleaning of blood by artificial methods is called dialysis. It is

done .by a machine called dialyzer. The blood of the patient is passed

through the dialyzer which contains dialysis fluid. Blood flows through

the tubes  of the dialyzer and dialysis fluid flows around these tubes.

The waste materials move from blood to the dialysis fluid.

cleansed blood is returned to the body.

 

1.12 IDENTIFY AND LABEL THE FOLLOWING DIAGRAMS.

a-

b-

 

CH:2 CELL DIVISION P:19-31

QUESTIONS

2.1 ENCIRCLE THE CORRECT OPTION.

 (i) Cell makes copies of its chromosomes during:

  1. interphase b. nuclear division of mitosis c. nuclear division of meiosis d. cytokinesis

(ii) The section of DNA which has information for making a specific protein is called:

  1. DNA strand b. nucleotide c. chromosome d. gene

(iii) Chromosomes are made of:

  1. DNA only b, proteins only c. DNA , proteins and fats d. DNA and proteins

(iv) The characters which are passed from parents to offspring:

  1. inheritable characters b. non-inheritable characters c. environmental characters d. natural characters

(v) An even that occurs during interphase:

  1. division of nucleus b. division of cytoplasm c. duplication of chromosomes d. formation of cell wall

(vi) Reduction of chromosomes takes place during;

  1. mitosis b. meiotic-I division b. meiotic-II-division d. both mitosis and meiotic-II-division

(vii) In humans, a sperm has 23 chromosomes. Egg cell has:

  1. 23 chromosomes B. 46 chromosomes c. no chromosomes d. 69 chromosomes

 (viii) Zygote is formed by the fusion of:

  1. two sperm cells b. two egg cells c. two somatic cells d. sperm cell and egg cell

(ix) In humans, the eye colour is developed due to the effects of:

  1. diet b. environment c. genes d. both ‘a` and ‘b’

(x) Which statement is correct?

  1. DNA has instructions for making proteins b. protein has instructions for making DNA c. both of these d. none of these

ANSWERS: (i-a) (ii-d)(iii-d)(iv-a) (v-c) (vi-b) (vii-a) (viii-d) (ix-c) (x-a)

2.2 MATCH THE WORDS OF COLUMN A WITH THE RELEVANT WORDS IN COLUMN B.

COLUMN A COLUMN B
1.     DNA

2.     Cytokinesis

3.     Free earlobe

4.     Zygote

5.     Egg

a)     Haploid cell

b)     Diploid cell

c)     Division of cytoplasm

d)     Gene

e)     Hereditary character

ANSWERS: (1-d)(2-c)(3-e)(4-b)(5-a)

 

2.3 GIVE SHORT ANSWERS.

(i) Name two inheritable characters,

Answer: 1. Eyes colour.  2. Free or attached earlobes.

(ii) Name two non-inheritable characters.

Answer: 1. Lost body organ of parent or weak body organ is not transferred to the children.

  1. Accidental loss of some part or damaged part due to accident.

(iii) What is gene?

Answer: The basic physical and functional unit of heredity is called gene.

(iv) Define heredity.

Answer: The transmission of characters from parent to offspring is called heredity.

(V) What are haploid cells?

Answer: The cells formed as a result. of meiosis with half number of chromosomes called haploid cells or gametes.

 

2.4 DESCRIBE MITOSIS.

Answer: MITOSIS

Mitosis is the process by which the parent cell divides into two

daughter cells with same number-of chromosomes.

 

(NECLEAR DIVISION)

Before mitosis (during interphase) two sets of chromosomes are

formed. During mitosis the nucleus of ‘parent cell divides and each set

of chromosomes is distributed in each -daughter nucleus.

(CYTOPLASMIC DIVISION)

After nuclear division a shallow groove arises in the middle of the cytoplasm which deepens further and divides the cell into two

daughter cells, each having a nucleus.

2.5 DESCRIBE MEIOSIS.

Answer:

Meiosis is the process by which the of cell divides two times to

form four daughter cells in. such a Way that the number of chromosomes in each daughters cell  reduced to half as compared to that in the parent cell.

MEIOTIC I DIVISION:

The process of meiosis consists of two divisions: meiotic I division and meiotic II division.

During meiotic I division, the number of chromosomes is reduced to half as compared to the parent cell.

MEIOTIC II DIVISION:

Meiotic II Division is similar to mitosis, because the half number of chromosomes is retained in the four daughter cells.

2.6 DEFINE HEREDITY AND DESCRIBE ITS IMPORTANCE IN TRANSFERRING A CHARACTERISTICS FROM PARENTS TO OFFSPRING.

Answer:

Ans. HEREDITY

The transmission of characteristics from parents to offspring is called heredity.

EXPLANATION

During reproduction, living things pass on their characteristics to their offsprings. This is the reason “that babies look like their parents. Plants grown from seeds resemble their parent plants.

 

 

2.7 DESCRIBE THE CHARACTERISTICS THAT CAN BE’ TRANSFERRED FROM PARENTSTO OFFSPRING.

Answer:

 HEREDITARY CHARACTERISTICS

The characteristics that are transmitted“ from parents to offsprings are called hereditary characteristics.

EXAMPLES

The characteristics such as the colour of eyes, skin colour, hair colour, free or attached ear lobes, height, intelligence etc., are the examples of hereditary characteristics,

2.8 WRITE NOTES ON: (a) DNA (b) Chromosomes (c) Genes

 

Ans DNA

According to Watson and Crick (Watson and Crick are two scientists who proposed DNA structure), the DNA molecule consists of two strands formed of nucleotides. ‘The two strands of DNA are linked with each other by cross bands like a ladder.

NUCLEOTIDES

DNA molecule is made of thousands of small units called nucleotides.

TYPES OF NUCLEOTIDES

In DNA, there are four types of nucleotides:

i- Adenine   (A) nucleotide

ii- Thymine (T)nucleotide

iii- Cytosine (C)nucleotide

iv- Guanine (G)nucleotide

In DNA strands, Adenine is always linked by Thymine; and Cytosine is always linked by Guanine.

FOR EXAMPLE

Adenine  Thymine

cytosine Guanine

Thymine Adenine

Guanine cytosine

 

 

Ans. CHROMOSOMES

Chromosomes are thread like structures found in the nucleus of a Cell. They appear as distinct. structure only during cell division.

 

 

 

CHROMATIDS

A typical chromosome consists of two arms called chromatids.

CENTROMERE

Chromatids are attached to the same part called centromere.

Ans. GENE

The basic physical and functional unit of heredity is called gene.

Genes act as instructions to make molecules called proteins. Genes occur in pairs.

GENE IS THE BASIS OF HEREDITY

Every hereditary character tin an organism e.g (tallness, dwarfness, eye color, free ear lobe, attached earlobe) is controlled by pair of genes; One member of a gene pair comes from male parent

(father) while the other comes from female parent (mother).

 

2.9 IDENTIFY AND LABEL THE FOLLOWING DIAGRAM:

Ch:3 BIOTECHNOLOGY32-44

QUESTIONS

3.1 ENCIRCLE THE CORRECT OPTION.

(i) The additional circular pieces of DNA present in a bacterial cell are called:

  1. RNA b. nucleotides c. chromatids d. plasmids

(ii)What may be the objective of genetic modifications of plants?

  1. production of disease resistant plants b. improvement in nutritional quality of plants c. production of herbicid resistant plants d. all of these

(iii)Plasmid and attached foreign gene with it are collectively called:

  1. recombinant cell b. recombinant DNA c. recombinant plasmid (L recombinant chromosome

(iv) The organisms whose cells and plasmids are usually used in genetic

engineering are:

  1. bacteria b. fungi d. algae d. fungi and algae

(v) Sections of DNA serving as codes for developing characters in an organism are called:

  1. genes b. nucleotides c. plasmids d, proteins

(vi) Which of the following is not a biotechnology product?

  1. insulin b. quinine c. beta-endorphin d. interferon

(vii) How do genetic engineers get insulin for diabetic patients?

  1. isolate from human pancreas b. isolate from pancreas of other animals c. insert insulin gene in human pancreas d. insert insulin gene in bacteria

(viii) Biotechnological method for the production of animal organs: il

  1. gene therapy b. genetic testing c. cloning d. organ transplant

(ix) Why do genetic engineers use bacteria in genetic engineering?

  1. the chromosome of bacteria is made of DNA and proteins b. their nucleus is very big and easy to handle c. they have many chromosomes d. bacteria divide very fast and make colonies

(X) A gene is inserted into a bacterium by:

  1. tissue culture b. fermentation c. biodegradation d. genetic engineering

ANSWERS: (i-d) (ii-d)(iii-b)(iv-a) (v-a) (vi-b) (vii-d) (viii-c) (ix-d) (x-d)

 

3 .2 MATCH THE STATEMENTS OF COLUMN A WITH THE RELEVANT STATEMENTS OF COLUMN B.

A B
1.     Growth hormone

2.     Beta-Endorphin

3.     Vaccine

4.     Interferon

5.     Insulin

a)     Viral infection

b)    Diabetes

c)     stimulating growth

d)    Immunity against diseases

e)     Pain killer

ANSWERS: (1-c)(2-e)(3-d)(4-a)(5-b)

 

3.3 GIVE SHORT ANSWERS.

(i) What is biotechnology?

Answer: Technology in which living things are used in different ways to help and benefit human being is called biotechnology.

(ii) What is genetic testing?

Answer: Genetic testing is the process by which genetic diagnosis of inherited diseases can be done. It involves the direct examination of DNA molecule. It is also used to determine a child’s paternity or a person ancestry.

(iii)  Name at least two life saving products of biotechnology.

Answer: 1. Insulin ——-à useful for diabetics

  1. Vaccines—-à used against many infectious diseases.

(iv) Briefly describe gene therapy.

Answer:

In this process, defective genes are supplemented or replaced by normal genes. It is used to cure genetic and acquired diseases like cancer and AIDS.

3.4 HOW DO SCIENTISTS INSERT THE GENE OF A DESIRABLE PROTEIN INTO A BACTERIUM?

ANSWER: There are two steps to insert a gene into bacterium:

FIRST STEP

The first step for inserting a gene into a bacterial cell is the

identification and isolation of the gene of desired protein from the

donor organism. An enzyme is used to cut the gene from the donor

organism. The isolated gene is then“ attached with plasmid” DNA taken

from the bacterium. The same enzyme (used for cutting the donor

gene) is used to cut end of the plasmid

RECOMBINANT DNA

The attached gene of desired ‘protein and the plasmid  are

collectively called recombinant DNA.

SECOND STEP

The recombinant DNA is inserted back into the same type of

bacterium from Which the plasmid was isolated, The bacterium which

takes in the recombinant DNA is called genetically modified bacterium

(GM bacterium) or transgenic bacterium.

i GM bacterium starts dividing and produces a bacterial colony.

Every bacterium of the colony contains a copy of gene of desired

protein. When bacterial colony grows, it starts making proteins under

the instructions of inserted gene.

In genetic engineering, genes of various useful proteins, e.g.

insulin and “enzymes for the synthesis of Various medicines, vaccines,

etc. are inserted in bacteria and desired proteins are obtained.

 

3.5 GIVE DIAGRAMMATIC EXPLANATION OF BIOTECHNOLOGICAL PROCESS FOR THE PREPARATION, G OF INSULIN.

ANSWER: Ans. Production of insulin by GMO  a

A Scientist insert the human insulin gene in bacteria to modify

them genetically. These genetically modified bacteria (GM bacterium)

prepare insulin.

The insulin prepared in GM bacteria is extracted from, bacterial

colonies and is used.

l The steps of biotechnology techniques for the production of

insulin are shown in figure.

 

  1. DESCRIBE THE APPLICATION OF BIOTECHNOLOGY IN AGRICULTURE.

ANSWER: APPLICATIONS OF BIOTECHNOLOGY IN AGRICULTURE

  1. Biotechnology has played a revolutionary role in improving our

agriculture and production of high yields of crops.

  1. Herbicides.(weed killing chemicals) and pesticides (insect killing

chemicals) are used to eliminate the crop enemies (Weeds and

insects).

Such chemicals also cause damage to the crop plants.

 

 

 

PROCESS OF MAKING PESTICIDES AND INSECTICIDES BY BIOTECHNOLOGY

  1. Using biotechnology, scientists insert weed resistant and pest

resistant genes into the plants». Such genetically modified plants

prepare proteins which are harmful for Weeds and pests/insects.

Cultivation of such , genetically modified crops improves the

quality of the crops and makes them safe‘ for human use.

CROPS THAT ARE MODIFIED

The majors crops that have been modified are maize (corn)Wheat,

rice, canola; potato, soybean, cotton, etc.

  1. Drought (water stress) and excessive salts (salinity) in the soil

also have harmful‘ effects on crop productivity. Biotechnologists

are Working to find genes that can enable crops to tolerate such

extreme conditions.

 

3.7 WHAT IS GENETIC MODIFICATION? HOW IS IT HELPFUL IN INCREASING THE AMOUNTS OF DIFFERENT NUTRIENTS IN FOOD?

ANSWER:

 

Q.9 Define genetic modification. Explain applications of

p genetic modifications.

Ans. The change in the genes of organisms using biotechnology

techniques is called genetic modifications.

The change in the genes» of an organism can be produced

through:

(i) Removal of genes.

(ii) Addition of genes.

(m) Repairing of genes.

It is the modern method to change the character of an organism.

Example

. This process is used in crops to produce resistance in plants

against disease causing microorganisms.

Similarly, the improvement in the nutritional quality of edible

plants is also one of the advancements of genetic modifications.

GENETICALLY MODIFIED ORGANISM

The organism Whose genes are modified is called genetically

modified organism (GMO).

IMPORTANCE OF GMO

Genetically modified organisms are used to prepare useful and

life saving products such as insulin and vaccines, etc.

 

3 . 8 DESCRIBE THE APPLICATION OF BIOTECHNOLOGY IN HEALTH AND ENVIRONMENT.

ANSWER:

 

  1. Biotechnology techniques are also used for curing diseases and

improving health;

  1. The diseases for which there was no adequate treatment can now

be treated.

  1. Identification of ‘root cause of diseases, production of medicines

for fighting against diseases and curing and correction of gentic

defects, etc.

  1. Various biotechnology products which are used to save lives:

(i)  INSULIN: useful for diabetics.

(ii) VACCINES: used against many infectious diseases.

(m) GROWTH Hormone: useful for stimulation growth.

(iv) BETAENDORPHIN: a pain killer drug.

(v) INTERFERON: antiviral proteins;

 

  1. Environmental problems, like pollution, degradation of land and

Water sewage water, etc. are resolved by using biotechnology.

  1. Microorganisms, e.g., genetically modified bacteria, are used to

treat sewage and refuse.

  1. These microorganisms are also used to clear spilled oil.
  2. These -microbes are used has bio-pesticides, bio-fertilizers,

biosensors, etc.

They all are prepared by using biotechnology techniques.

 

CH:4 POLLUTANTS & THEIR EFFECTS ON ENVIRONMENT P:45-60

QUESTIONS

4.1 ENCIRCLE THE CORRECT OPTION.

i- Indicate an air pollutant among the following:

  1. oxygen b. nitrogen c. water d. carbon monoxide

ii-The gas which is responsible to stop ultraviolet radiation coming hom the Sun:

  1. carbon dioxide b. sulphur dioxide c. ozone d. nitrogen

iii-Which of the following is not a greenhouse gas?

  1. methane b. carbon dioxide c. sulphur dioxide d. Water

iv- The pollutants which arc mainly responsible for ozone depletion arc:

  1. oxides of carbon b. oxides of sulphur c. oxides of nitrogen d. chlorofluorocarbons

v- Identify the chemicals which cause the rain to become acidic:

  1. oxides of carbon and dust particles b. oxides of sulphur and nitrogen c. solid particles of carbon and lead d. chlorofluorocarbons.

vi- Reason for increase in the amount of carbon dioxide in air:

  1. plantation b. deforestation c. using CFC-free products d. recycling of materials

vii-Which air pollutant when attaches itself with haemoglobin, reduces its oxygen carrying capacity?

  1. carbon dioxide b. sulphur dioxide c. oxides of nitro gen d. carbon monoxide

viii-The phenomenon which does not lead to global warming:

  1. greenhouse effect b. ozone depletion c. deforestation d. photosynthesis

ix- Glass and styrofoam are the examples of:

  1. biodegradable materials b. non-biodegradable materials c. harmful products d. air pollutants

 x-The amount of which greenhouse gas you can reasonably control?

  1. oxides of nitrogen b. water vapours c. methane d. carbon dioxide

ANSWERS: (i-d) (ii-d)(iii-c)(iv-d) (v-b) (vi-b) (vii-d) (viii-d) (ix-b) (x-d)

 

4.2 WRITE SHORT ANSWERS.

  1. What are the main air pollutants?

ANSWER: Carbon mono oxide (CO), Sulphur dioxide (S02) oxides of nitrogen (NO) and (NO2).

 

  1. Name greenhouse gases.

ANSWER: Carbon dioxide, methane, oxides of nitrogen, water vapours, etc

are called greenhouse gases.

 

iii. Name the acids which are present in the acid rain?

ANSWER: Sulphuric acid (H2S04).

Nitric acid (HNO3).

 

  1. Ozone layer is important. Why?

ANSWER: Ozone layer prevents to enter ultraviolet rays to the earth. These rays are harmful for life.

 

  1. R strategies stand for what?

ANSWER: 3R strategies are “Reduce-Reuse-Recycle”

 

  1. Write down the names of three such products which can be recycled.

ANSWER: (i)aluminum cans  (ii) paper (iii) glass

vii. Name common methods which are used for solid waste management.

ANSWER: (i)landfill (ii)incineration (iii)recycling

 

viii. How does ozone depletion contribute towards global warming?

ANSWER:

              Due to ozone depletion, UV-rays can enter into the earth and the temperature of the earth is increasing and earth globe is getting warmer. This is called global warming

  1. Sulphur dioxide is an important pollutant. From where does it enter atmosphere?

ANSWER:

 

(ix) Sulphur dioxide is an important pollutant. From Where does it enter the atmosphere?

Ans. Sulphur dioxide. is produced by burning of coal or oil in factories.

 Smoke released from thermal powers stations usually contain A d sulphur dioxide.

 

4.3 DESCRIBE THE ADVERSE EFFECTS OF CARBON MONOXIDE ON HUMAN ORGAN SYSTENIS.

ANSWER:

EFFECTS OF CO GAS

It causes headache;

It causes brain damage and respiratory problems.

When CO reaches our blood, it gets bonded with haemoglobin and reduces it oxygen carrying capacity.

EFFECTS OF SULPHUR DIOXIDE (SO2)

It dissolves in Water and causes acid rain.

Exposure to SO2 causes breathing difficulties, pneumonia, lung cancer.

It can cause-cardiovascular diseases.

It can also cause cancer of lungs.

Sulphur dioxide destroys chloroplasts in plants and plant growth is affected.

EFFECTS OF OXIDES  OF NITROGEN

They dissolve in Water and cause acid rain.

They have severe effects on lungs and damage them.

Nitrogen oxide can damage plants and buildings when dissolved in water as acid rain.

 

4.4 EXPLAIN THE FOLLOWING PHENOMENA AND THEIR EFFECTS ON THE ENVIRONMENT.                            a) greenhouse effect b) global warming c) acid rain d) ozone depletion

ANSWER:

ANS.

(a) GREENHOUSE EFFECT

When sunlight falls on the Earth, a small part of it absorbed by the Earth and is converted to heat energy. A part of this heat energy is reflected by the Earth back to the atmosphere. Some gases present in the atmosphere, e.g., carbon -dioxide,’ methane, oxides of nitrogen,“ water vapours; etc., trap apart of the heat reflected by the Earth causing increase in the atmospheric temperature, These gases are called! greenhouse gases and the phenomenon “is called greenhouse effect.

 

(b) GLOBAL WARMING

                      Due to human activities like burning of fuel, etc., the amount of

greenhouse gases‘ is increased inthe atmosphere. This speedsiup the

greenhouse ‘effect. The increasing rate of greenhouse effect and ozone

depletion is increasing the average temperature of the earth. As a

result, the Earth globe is getting warmer. This is called global

warming.

              Due to global Warming, the ice in the Polar Regions and at the Mountains melts at a greater rate. This leads to the rising in the level of sea Water which creates floods in low coastal areas. the climate of many regions of the world’ is also changing due to global warming .

The global warming is thus a threat to the life on the Earth.

 

EFFECTS OF GLOBAL WARMING

  1. Due to global Warming, the ice in the Polar region and at the

mountains, melts at a greater rate. ”

  1. Due to melting of ice, sea‘ water level is rising that is creating

 floods in low lying coastal areas.

  1. The climate of many regions of the World is also changing due to

global warming. So, the global warming is a major threat to the life on the earth;

 

(c) EFFECTS OF ACID RAIN

  1. Oxides of sulphur and nitrogen get mix with water and form rain water acidic which spoils trees and plants.
  2. Acid rain kills aquatic life.
  3. Acid rain erode the stone work
  4. A Corrosion of metals is caused by acid rain.
  5. The acidic water makes soil acidic.
  6. Microorganism present in soil are also affected by acid rain.

(d) OZONE DEPLETION

A layer of ozone (O3) ifl the upper atmosphere of the Earth stops the ultraviolet rays coming from the  to the Earth. In this way, the living things on the Earth remain safe from harmful effects of the ultraviolet radiation coming from the Sun.

 

Chlorofluorocarbons (CFCs) which are used in air conditioners, refrigerators, spray cans, etc., enter the air on leakage from these appliances. On reaching the ozone layer, they react with ozone and cause thinning of this layer. Hence, the ozone layer is depleted. The phenomenon is called ozone depletion.

Through the thin ozone layer, ultraviolet rays of the Sun pass and reach the Earth. On reaching the Earth, they affect the life by causing serious diseases like skin cancer and eye problems, etc. these ultraviolet rays also increase the temperature of the Earth.

 

4.5 POINT OUT THE SOURCES OF AIR POLLUTANTS YOU FIND IN YOUR LOCALITY AND SUGGEST  TO REDUCE THE POLLUTION PRODUCED FROM THESE SOURCES.

ANSWER:

SOURCES OF AIR POLLUTANTS

  1. Poisonous gases are produced during the decay of dead organic Matter These gases are carbon monoxide (CO), sulphur dioxide (S02), oxides of nitrogen (N O and N02) chlorofluorocarbons (CFCs), etc, are the main air pollutants.
  2. Carbon monoxide is produced by the incomplete combustion of coal and other fossil. fuels (natural gas, petrol, oil) smoke released from motor vehicles industries are the main source of CO.
  3. Sulphur dioxide is produced by burning of coal or oil in factories.
  4. Oxides of nitrogen produced by ‘burning of coal and oil at high temperature in industries.
  5. Chlorofluorocarbons (CFCs) are the compounds which contain chlorine fluorine and carbon atoms.

 

SUGGESTIONS TO REDUCE THE POLLUTION

All of us are responsible for keeping the environment clean. Following measures can be taken to reduce air pollution:

  • Instead of personal car, public transport should be used for travel.
  • Sulphur and lead free fuels should be used.
  • Domestic trash and other solid Wastes should, not be dumped on open Places.
  • Factories and industries should be shifted away from urban areas.
  • Acidic industrial exhaust must be neutralize and then release in the air.
  • Engines of vehicles should be tuned properly.
  • CFC- free products should be used.
  • 3R-Strategies of Reduce-Reuse-Recycle should be adapted.
  • Trees should be grown along the road.
  • Deforestation should be avoided.

 

4.6 SUGGEST WHAT CAN FOLLOWING COMMUNITIES DO TO REDUCE AIR POLLUTION. a) students b) farmers c) factory owners d) scientists

ANSWER:

STUDENTS

There are different responsibilities for different’ communities.

  1. Wrappers of chips, toffees, biscuits must be thrown in collecting
  2. Cans of juices “and drinks must be collected and never be thrown in open places.

iii. They should not Waste extra paper.

FORMERS.

  1. Formers must use natural resources carefully. They should not cut trees for cultivation.
  2. Less use of herbicides and pesticides must be done, because these chemicals spoil the soil and underground Water.

iii. Use of fuels in machinery should be very wise.

FACTORY OWNERS

  1. Factory Wastes must be treated before disposing them.
  2. Waste gases should be neutralizes before entering in the air.

iii.  Factories should be shifted far from urban areas.

SCIENTISTS

  1. Scientists must recycle chemicals and solids.
  2. Less use of resources must be done.

iii.Wastage of resources must be stopped and checked.

 

4.7 WHAT IS DEFORESTATION? EXPLAIN ITS EFFECTS ON WILDLIFE.

ANSWER:

 

 

Q.11 Define and explain deforestation.

Ans. DEFORESTATION

The destruction of forests as a result of human activities is called deforestation;

BENEFITS OF FORESTS

                        Forests are our great Wealth. They bring favourable changes in the climate of an area.

  1. They stop storms and bring rains.
  2. They are the source of many -useful materials such as timber, firewood resins, gums, and medicines etc.
  3. They prevent soil erosion.
  4. They provide habitat to a Wide variety of Wild life.

              All non-cultivated plants and non-domesticated animals of an area are collectively called Wild life.

  1. Deforestation destroys the habitats of wild life.

2.The extinction risk of Wild life is increased.

  1. Natural balance maintained by the wild life is disturbed.

 

4.8 WHAT TYPES OF CLIMATIC CHANGES CAN APPEAR BY DEFORESTATION?

ANSWER:

           EFFECTS OF DEFORESTATION

  1. Deforestation has “many adverse effects on the environment. It changes weather and climate.
  2. Roots of trees hold the soil. Cutting of tree leads to soil erosion and fertile part of the soil is lost through this process.
  3. Rate of evaporation is reduced which results in less rain.
  4. Deforestation decreases carbon dioxide consumption by plants Deforestation increasing its amount in the environment.

5.This leads to the increased greenhouse effect and global warming.

 

4.9 SUGGEST WAYS FOR PROPER MANAGEMENT OF SOLID WASTES.

ANSWER:

CONSERVATION OF RESOURCES

Unwise use of fossil fuels must be stopped and they need to be conserved.

      There are three strategies:

  1. Reduce
  2. Reuse

iii. Recycle.

Can be adopted for conservation of resources.

REDUCES

The use of non biodegradable objects should be reduced and the resources which -are used’ in their manufacture should be conserved.

REUSE

The second step is reuse; In this step, the non-biodegradable objects should be used again and again instead of throwing them after first use.

RECYCLE

The third strategy  recycling. The waste objects of non biodegradable ‘materials should be

collected, cleaned, melted and refolded into new objects.

By adopting (3R strategies) we  can conserve our resources.

 

4.10  RECYCLING IS GOOD PRACTICE TO CONSERVE NATURAL RESOURCES. EXPLAIN.

ANSWER:

Same 4.9

4.11 WHAT SHOULD WE DO TO ADOPT SR STRATEGIES FOR CONSERVATION OF RESOURCES? 

ANSWER:

          All of us are responsible for ‘keeping the environment clean.

Following measures can be taken to reduce air pollution:

  1. Instead of personal car, public transport should be used for travel.
  2. Sulphur and lead free fuels should be used.
  3. Domestic trash and other solid wastes should. not be dumped on open Places.
  4. Factories and industries should be shifted away from urban areas.
  5. Acidic industrial exhaust must be neutralize and then release in the air.
  6. Engines of vehicles should be tuned properly.
  7. CFC- free products should be used.
  8. 3R-Strategies of Reduce-Reuse-Recycle should be adapted;
  9. Trees should be grown along the road
  10. Deforestation should be avoided.

 

 

4.12 CONTROLLING POLLUTION IS A RESPONSIBILITY FOR ALL, WHAT WOULD YOU SUGGEST FOR INDIVIDUALS, THE ORGANIZATIONS AND THE GOVERNMENTS TO SHARE THIS RESPONSIBILITY?

  ANSWER:

Same 4.11

CH:5 CHEMICAL REACTIONS P:61-77

QUESTIONS

5.1 ENCIRCLE THE CORRECT OPTION.

(i) Carbon burns in air to release energy al ogg with the formation

  1. carbon dioxide b. carbon dioxide and water c. carbon dioxide and hydrogen d. carbon monoxide and water

(ii) The products of the reaction between zinc and dilute sulphuric acid a

  1. Zinc oxide and water b. Zinc sulphide and water c. Zinc sulphate and hydrogen d. Zinc sulphide and hydrogen

(iii)Which of the following is an unbalanced chemical equation?

a, CH4(g) + 2O2(g) —> 2H2O(g) + CO2(g)                          b. Na(s) + Cl2(g) —> NaCl(s)                                            c. C(s) + Cu2O(s) —> CO(g) + 2Cu(s)                                 d. Co) + O2(g) —> CO2(g)

(iv) Heating of solid potassium chlorate produces a gas:

  1. chlorine b. carbondioxide c. carbonmonoxide d. oxygen

(v) Which of the following is an exothermic reaction?

  1. Formation of iron sulphide by heating the mixture of iron and sulphur. b. Formation of nitric oxide by heating the mixture of nitrogen and oxygen. c. Formation of hydrogen iodide by heating the mixture of hydrogen and iodine.                                                                                                                                                                                                                                                                                                              d. Formation of calcium oxide and carbon dioxide by heating calcium carbonate.

(vi) Which of the following is a balanced chemical equation?

  1. Fe + 3Cl2—> 2FeCl3 b. Fe + 3Cl2 —> FeCl,                                                     c. 2Fe + 3Cl2 -> 2FeCl3                                                         d. Fe + C12 —> FeCl,

(vii) The following equation is properly balanced when: x CO (g) + y O2(g)—> z CO2(g)

  1. x=l, y=2 and z=3  b, x=2, y=1 and z=l                                                            c. x=2, y=2 and z=2                                                                   d, x=2, y=1 and z=2

(viii)How many oxygen atoms are present in one molecule of Mg (HCO3)Q?

  1. 2 b. 4 c. 6     d. 8

(ix) The reaction between calcium oxide and carbon dioxide to form calcium carbonate is an example of:

  1. addition reaction b. decomposition reaction c. acid-base reaction d. neutralization reaction

( x) Thermal decomposition of calcium carbonate produces a gas:

  1. oxygen b. carbon dioxide c. calcium d. carbon monoxide

ANSWERS: (i-b) (ii-c) (iii-b)(iv-d) (v-a) (vi-c) (vii-c) (viii-c) (ix-a) (x-b)

 

 5.2 ANSWER THE FOLLOWING QUESTIONS BRIEFLY.

(i) Define a chemical reaction.

ANSWER: A reaction in which properties of reactants and products are

chemically different. They both are totally different.

(ii) What are reactants?

ANSWER: The substances which take part in a chemical reaction are called reactants.

(iii) What are products?

ANSWER: The substances which are formed as a result of the reaction are called products.

(iv) What is a chemical equation?

ANSWER: Chemical equation is the representation of a chemical reaction in terms of symbols, formulae and signs.

(v) State the law of conservation of mass.

ANSWER: This law states that during a chemical reaction, mass is neither created nor destroyed but it changes from one form to another. In other words during a chemical reaction, total mass of the products is equal to the total mass of the reactants.

 

5.3 DIFFERENTIATE BETWEEN THE FOLLOWING.

(i) Addition reaction and decomposition reaction.

ANSWER:

Addition reaction Decomposition  reaction
The chemical composition of two or more substances to form one compound is called addition reaction. A chemical reaction in which a compound splits up into two or  more simple substances is called

decomposition reaction.

2. Examples

2H2(g)+ 02 —-> 2H2O(g)

H2(g)’+ Clz(g)———-> 2HCl(g)

2. Examples

                        Heat 

2KCl O3(S) ————-—> 2KCl(s) + 3O2(g)

                       Heat

CaCO3(s) —————> CaO + CO(g)

 

(ii) Balanced chemical equation and unbalanced chemical equation.

ANSWER:

Balanced chemical equation unbalanced chemical equation.
1. The equation in which number of each element on both sides of the equation, reactant side and produce size are equal. The equation in which number of atoms of each

element on both sides are not equal.

2. Examples

H2(g)+vCl2(g) ———->  2HCl(g)

2. Examples

Fe + O2 ———> Fe2O3(s)

 

(iii) Exothermic reaction and endothermic reaction.

ANSWER:

Endothermic reaction Exothermic reaction
1. The reaction in which heat is absorbed is called endothermic reaction. 1. The reaction during which heat is given out.
2. Examples

heat

CaCo3 ————à CaCo(g) + CO2(g)

Examples: Burning of fuel in homes produce

heat, which We use in kitchen.

 

5.4 COMPLETE AND BALANCE THE FOLLOWING INCOMPLETE EQUATIONS.

(i) Mg(s) +02 (g) ————-à

(ii) CH.(g) +02(g) ————-à

(iii) Fe(s) + S (s) ————-à

(iv) N2(s) + H2(g) ————-à

(V) Na (S) + Cl2 (g) ————-à

2MgO

CO2 + 2H2O + Heat

FeS

2NH3

2NaCl

 

5.5 BALANCE THE FOLLOWING EQUATIONS.

(1) Ca(HCO3)2+ HCl –>  CaCl2 +CO2 +H2O

 

(ii) NaBr +Cl2—> NACl +Br

 

(iii) Fe (s) +O2à Fe2O3

 

(iv) NH4OH + H2SO4 à (NH4)SO4 +H2O

 

(v) Zn + HCl à ZnCl2 +H2

CaCl2+ 2CO2 + 2H2O

2NaC1  + Br2

Fe2O3

(NH4)2SO4+ H2O

ZnCl2  + H2

 

 

 

 

5.6 WHEN COAL BURNS, IT LEAVES ASH BEHIND. ASH SO PRODUCED IS LIGHTER THAN THE COAL WHICH HAS BURNT. JUSTILY THE DECREASE IN MASS IN THE LIGHT OF LAW A CONSERVATION OF MASS.
Answer:

When coal burns, it leaves ash behind. Ash so produced is lighter than the coal which has burnt. Justify the decrease in mass in the light of law of conservation of mass.

When coal burns. It leaves ash behind. Ash is produced so lighter than the coal which has burnt. According to law of conservation of mass, matter never be created not destroyed but it changes from one form to another. Then why coal is heavier than ash behind after burning. The answer is that during process of burning some gas» are also released in air. If we Weighs them their weight and ash Weight will be exactly equal to the coal which has burnt.

5.7 WRITE AT LEAST TWO EXAMPLES OFTHE FOLLOWING CHEMICAL REACTIONS.

(i)  Addition reaction (ii) Decomposition reaction  (iii) Exothermic reaction (iv) Endothermic reaction

Answer:

(i)ADDITION REACTIONS

      The chemical combination of two or more substances to form one compound is called addition reaction. The following are the examples of addition reactions:

i.  2H2(g) + O2(g) —> 2H2O(g)

Hydrogen and oxygen combine to form water.

ii. H2 + Cl2(g) + 2HCl(g)

 Hydrogen gas and chlorine gas combines to form hydrochloric acid.

 (iii) Na(s)   + 3H2(g)   2,N——- >2 NH3(g)

Nitrogen gas and hydrogen gas combines to form ammonia gas.

(iv) 2Mg  + O2(g) ——– > 2MgO(s)

 Magnesium reacts with oxygen gas to form magnesium oxide.

(v) 2Na(s) + C12(g)  ———> NaCl(S)

                  Sodium metal reacts with chlorine gas and forms sodium chloride in solid form.

These all are examples of addition reactions because two elements combine to form one compound.

 

(ii) DECOMPOSITION REACTIONS

                                A chemical reaction during which a compound splits up into two

or more simple substances is called decomposition.

 

 

 

Usually heat is required to bring about decomposition of compounds.

Examples

                            Heat

i. 2KClO3(s) ———- > 2KCl(s) + 302(g)

Potassium chlorate decomposes or splits into two compounds that are potassium chloride and oxygen.

                        Heat

ii. CaCO3(s) ———> CaO(s) + CO2(g)

Calcium carbonate decomposes into two compounds that are calcium oxide and carbon dioxide. i .

                                   Heat

iii. 2Pb(NO3)2(s) ———-> 2PbO  + 4NO2(g) + O2(g)

                Lead nitrate is decomposed into lead oxide and nitrogen dioxide with oxygen gas.

 

(iii) EXOTHERMIC REACTION

         Exo (outside) and therm means (heat).

Exothermic reactions are those reactions during which heat is given out.

 

Examples

i. Burning is a common example of exothermic reaction.

CH4(g) + O2(g)  H CO2(g)+ H2O(g) + Heat

 

ii. Fossil fuels (coal, natural gas, etc) burns in the air to release heat

C(s) + H O2(g) ——>  CO2(g) + Heat

iii. Iron burns with sulphur to form iron sulphide and heat.

Fe(s) + S(S) ———–> FeS(s) + Heat 

               During this activity, sides of the beaker become Worm due to releasing of heat.

CaO(s) + H20——->  Ca(OH)2(aq) + Heat

(iv) ENDOTHERMIC REACTION

                      Endo means (inside) and therm means heat. The reaction during which heat is absorbed are called endothermic reaction.

Examples

i. Thermal decomposition of calcium carbonate

CaCO3(g) + Heat ————> CaO(s) + CO2(g)

 

ii.  Reaction of calcium chloride with sodium carbonate

                 During this activity We will feel that the sides of the baker become cold. It happens sddue to endothermic reaction.

CaCl2(aq) + Na2CO3  + Heat(aq)——>  CaCO3(s) + 2NaCl(aq)

iii. Formation of Nitric oxide from oxygen and nitrogen

     When nitrogen gas reacts with oxygen, heat is absorbed so it is endothermic reaction.

N2(g)  + K  O2(g) +  Heat  2NO2(g)

 

 

5.8 HOW DO THE FOLLOWING REACTANTS REACT TOGETHER. WRITE DOWN COMPLETE REACTIONS & BALANCE THE RESULTING EQUATIONS.

(i) Iron + Hydrochloric acid

(ii) Calcium oxide + Carbon dioxide

(iii) Carbon monoxide + Oxygen

(iv) Methane + Oxygen

(v) Carbon dioxide + Water

Fe                    HCl                                    FeCl2        + H2

Iron + Hydrochloric acid——> Ferrous chloride+ hydrogen

 

CaO                          O2                            CaCO3

Calcium oxide +  Oxygen ——> Calcium carbonates

 

CO                                    O2                         C02

Carbon monoxide + Oxygen——> carbon dioxide

 

CH4                 O2                                   CO2     + H2O

Methane +  Oxygen ——> carbon dioxide+ Water

 

  C02                          H20                       H2CO3

 

Carbon dioxide + Water ——> carbonic acid

 

5.9 DESCRIBE THE APPLICATIONS OF CHEMICAL REACTIONS.

ANSWER:

CHEMICAL REACTION

                  When two or more substances combine chemically or done substance decompose into of two different substances. Their properties and chemical composition is properties and chemical

is entirely different. This is a chemical reaction.

APPLICATIONS OF CHEMICAL REACTIONS

                We deal with large number of chemical reactions, atoms present

in different substances rearrange themselves from new substances.

  1. BURNING OF COAL

                     Burning of coal and natural gas in air is the example of chemical reaction, Coal is the chemical reaction. Coal is the chemical form of carbon, when it combines with oxygen in air it forms carbon dioxide which is entirely different from carbon.

 

Rearrangement of atoms during chemical reaction of carbon with oxygen

 

  1. BURNING OF METHANE (NATURAL GAS) IN AIR

                 When methane burns in air carbon dioxide and H20 molecules, are formed, methane is different chemically from its products.

Rearrangement of atoms during chemical reaction of methane with oxygen

 

 

iii. REACTION OF HYDROGEN GAS WITH OXYGEN GAS

The rearrangement of atoms during the chemical reaction of hydrogen with oxygen to form liquid water is shown below:

Rearrangement of atoms during chemical reaction of hydrogen with oxygen

 

5.10 WRITE DOWN THE RULES FOR BALANCING CHEMICAL EQUATIONS.

ANSWER:

            An equation can be balanced by different methods. The trial and error method is commonly used.

TRIAL & ERROR METHOD

According to this method trial and error process of adjusting coefficient before symbols and formulae is continued till the numbers of atom-s of each side of the equation become equal.

 

5.11 DESCRIBE THE IMPORTANCE OF EXOTHERMIC REACTIONS IN EVERYDAY LIFE.

ANSWER:

THE IMPORTANCE OF EXOTHERMIC REACTIONS IN EVERYDAY LIFE

  • 1- reaction of barium hydroxide octahydrate crystals with dry ammonium chloride
  • dissolving ammonium chloride in water
  • 2- reaction of thionyl chloride (SOCl2) with cobalt(II) sulfate heptahydrate

mixing water and ammonium nitrate

3- Mixing water with potassium chloride

  • 4- reacting ethanoic acid with sodium carbonate

5- photosynthesis (chlorophyll is used to react carbon dioxide plus water plus energy to make glucose and oxygen)

 

5.12 GIVE TWO EXAMPLES OF CHEMICAL REACTIONS FROM EVERYDAY LITE WHICH ARE ESSENTIAL FOR LIFE.

ANSWER:

IMPORTANCE OF EXOTHERMIC REACTIONS IN DAILY LIFE

  • Exothermic reactions are important to forensic sciences and particularly to fire and explosion investigation. When a chemical reaction requires heat (rather than producing it) and results in cooling down the surroundings, it is conversely called endothermic.
  • Exothermic reactions occur in many phenomena and applications of every-day life. The speed at which they occur can range from extremely slow to extremely fast. For example, an exothermic reaction occurs when a piece of steel rusts. Rust is iron oxide (Fe2O3), which is produced by the reaction of iron (Fe) with oxygen (O2).
  • An explosion is also an exothermic reaction. Even if the end result of an explosion is the high pressure generated that pushes everything away from its seat, heat is first produced in great magnitude.
  • All combustion reactions are exothermic. In a fire investigation, it is important to know what kind of chemical reaction occurred and caused a fire.

CH:6 ACIDS, BASES/ALKALIS AND SALTS P:78-98

QUESTIONS

6.1 FILL IN THE BLANKS.

i- Acids react with bases to form Water and—————————

ii-Vinegar contains———————- acid.

iii- Tartaric acid is present in———————

iv- Bases have———————– taste.

v-All alkalies are bases but all bases are not———————

vi-Bases have—————- touch.

vii-Sodium hydroxide is also called——————–

ANSWERS: (i-salts) (ii-acetic) (iii-tamarind, grapes)(iv-bitter) (v-alkalies) (vi-soapy) (vii-base / alkali)

 

6.2 PUT (√) FOR CORRECT & (X) FOR INCORRECT STATEMENT

  1. Acetic acid is found in grapes.
  2. All carbonates react with mineral acids liberating CO2 gas.
  • Acids turn red litmus blue.
  1. All bases do not dissolve in water.
  2. Solution of a base has a soapy touch.

ANSWERS: (i- F) (ii-T) (iii-F)(iv-F) (v-T)  

 

6.3 ENCIRCLE THE CORRECT OPTION.

(i) The king of chemicals is

(3) KOH (bi HCl (c) H2SO4 (d) NaCl

(ii) Sodium hydroxide solution in water will:

(a) turn blue litmus red (b) give pink colour with phenolphthalein (c) give red colour with methyl orange (d) not affect the phenolphthalein indicator

(iii) When carbon dioxide is passed through lime water, the milkiness is due to the compound:

(a) Ca(HCO3)2(b) CaCO3 (e) H2 CO3 (d) CaO

(iv) Lactic acid is found in:

(a) Grapes  (b) Tomatoes (c) Ant’s string (d) Curd

(V) Which is not the salt of phosphoric acid?

(a) Na2PO4 (ii) Na H 2PO2 (c) Na2HPO3 (d) Na 2HPO4

(vi) Sodium carbonate is an important salt used for many purposes if industries. Sodium hydroxide is made to react with which acid to get it?

(a) oxalic acid (b) citric acid f (c) carbonic acid (d) acetic acid

 ANSWERS: (i-C) (ii-B) (iii-B)(iv-D) (v-C) (vi-C)

 

 

6.4 GIVE SHORT ANSWERS.

(i) Define an acid.

Answer: Acid are compounds Which gives H+ ions in aqueous solution.

(ii) Name three mineral acids.

Answer: Hydrochloric acid, nitric acid, sulphuric acid.

(iii) State three properties of acids.

Answer:

  1. Then gives hydrogen ions in aqueous solution.
  2. They react with metals to give hydrogen gas.

iii. They have sour taste.

(iv) Mention the uses of two salts in industries.

Answer: 1. NaCl is used to manufacture chlorine, HC1, Ca(OH)3 + NaOH.

  1. N &2CO3 is used for softening hardware for manufacture of soap.

(v) Name a salt which can reduce the acidity in our stomach.

Answer: NaHCO3

(vi) What happens when a salt like copper sulphate reacts with water?

Answer: It becomes aqueous solution. Now it can pass electricity.

(vii) Is soda Water acidic or basic? V

Answer: Basic

(viii) Which alkali is commonly used to open a drain?

Answer: Sodium hydroxide

(ix) Write down the chemical equation showing the reaction of ammonia and water.

Answer: NH3 + H2O———> NH4OH.

(x) How is litmus solution is prepared?

Answer: Blue ionic mixes with Water.

 

6.5 WHAT IS THE EFFECT OF DILUTE HCI ON THE COLOURS OF THE FOLLOWING? (i) methyl orange (ii) phenolphthalein (iii) blue litmus

Answer: (i) Red  (ii) Colourless A (iii) Red .

6.6 WHAT IS A BASE? WRITE DOWN THE NAMES AND FORMULAE OF FOUR BASES.

Answer:                                                                                                                                                                                 Citric acid, Tartaric Acid,   Acetic acid                                                                                            Citrus fruits  Tamarind, grapes Vinegar

6.7 MENTION THE SOURCES OFTHE FOLLOWING.  (i) citric acid (ii) tartaric acid (iii) acetic acid

Answer: (i) citrus fruits (ii) grapes  (iii) vinegar

6.8 WHAT LS THE ACTION OFCAUSTLC SODA ON THE COLOUR OFTHE FOLLOWLNG. (i) red litmus (ii) phenolphthalein (iii) methyl orange

Answer: (i) blue  (ii) pink p (iii) yellow .

6.9 DESCRIBE HOW ARE SALTS USEFUL FOR THE HUMAN BODY.

Answer: Salts of sodium, potassium, calcium, magnesium and iron are needed for the normal working of our body. They perform the  following functions;                                                                        (a) Sodium and potassium salts are needed for the proper functioning of muscles and the nervous system.                                                                                                                                                 (b) Salts of calcium are present in bones. They are responsible for the strength of bones. These salts are responsible for preventing heart attacks. Plaster of Paris-(CaSO4.. 5 H20) is used for broken limbs.                                                                                                                                        (c) Potash alum is used to coagulate the blood coming out of a wound. It is also used for the purification of water.                                                                                                                                (d) Salts of iodine are needed for the proper functioning of thyroid glands. They are also used to set the treatment of goiter.

6.10 WHAT HAPPENS WHEN:                                                                                                                                              (i) Magnesium reacts with dilute HCl?                                                                                                                  (ii) Sodium hydrogen carbonate reacts with dilute h2so,?                                                                                (iii) Copper oxide reacts with dilute sulphuric acid?                                                                                            (iv) Sodium reacts with chlorine?

Answer:                                                                                                                                                                 (i) Salt + hydrogen gas forms.                                                                                                                   (ii) Sodium sulphate + CO2 + H20 forms.                                                                                                           (iii) Copper sulphate + H20 forms.                                                                                                                          (iv) NaCl sodium chloride forms.

6.11 WHY THE AQUEOUS SOLUTIONS OFNNI~ICO, AND NA,C0, ORC BULC IN NATURE?

Answer: Because they both turns red litmus blue. They both have soapy aqueous solution.

6.12 HOW DOES THE SOIL BECOME AC IDIC?

Answer: By acidic rain which contain nitrogen and sulphur oxides.

6.13 SULPHURLC ACLRL (H2S02) MOLECULE CAN GIVE TWO PROTONS LN WATER WHEREAS HYDROCHLORIC ACID MOLECULE CAN GIVE ONLY ONE PROTON. DOEL THAT MEAN SULPHURIC MELD LI TWLCE LL STRONG AN ACID AS HYDROCHLORIC MELD?

Answer: Yes H2804 is more strong than HCI.

6.14 INDICATE IN FRONT OF EACH SALT THE ACID AND THE BASE WHICH HAVE BEEN USED TO PRODUCE THEM.

CALCIUM ACETATE, POTASSIUM HYDROGEN SULPHATE, MAGNESIUM NITRATE, AMMONIUM OXALATE, SODIUM POTASSIUM TARTARATE, FERRIC CHLORIDE

Name of salt  Acid Base
i- CALCIUM ACETATE Acitic acid A Calcium hydroxide
ii- POTASSIUM HYDROGEN SULPHATE Sulphuric acid Potassium hydroxide A
iii- MAGNESIUM NITIATE Nitric acid Magnesium hydroxide
iv- AMMONIUM OXALATE Oxalic é acid Ammonium hydroxide
v- SODIUM POTASSIUM TARTARATE Tartaric acid Sodium hydroxide
vi- FERRIC CHLORIDE Hydrochloric acid Ferrichylroxide
ANSWERS: (i-                        ) (ii- Potassium hydrogen sulphate) (iii- magnesium nitrate,) (iv- ammonium oxalate,)(v- sodium potassium tartarate,) (vi- ferric chloride.)

 

CH: 7 FORCE AND PRESSURE  P:99-112

QUESTIONS

7.1 ENCIRCLE THE CORRECT OPTION.

(i) The SI unit of pressure is:

  1. watt b. joule c. Pascal d. Newton

(ii) When same amount of force is applied on different areas, it exerts

a, low pressure on small area. b. no pressure on small area c. high pressure on small area. d, high pressure on large area

(iii) (A pressure of l0Nm 2  is equal to:

a, l 0Pa  b. 1 00Pa  c. 1000Pa  d. l0,000Pa .

(iv) A force of l800N is acting on the surface area of 0.06m1. The pressure exerted by the force will be:

a, 3 kPa b. 30 kPa c. 300kPa d. 3000 kPa

(v) Hydrostatic pressure of the liquids depends on:

  1. shape of the vessel b. size of the vessel c. volume of the vessel d. depth of the liquid

(vi) People on hills experience atmospheric pressure:

  1. more than that at the sea level b. less than that at the lea level c. same as that at the sea level d. four times more than that at the sea level

(vii)When the plunger A shown in the figure is pushed:

a, plunge B will move out more than C    b, plunge C will move out more than B                                          c. Both B & C move out equally.    d, neither B nor C will move out C

(viii) A gas in a container develops pressure due to:

  1. collision of molecules with each other b, collision of molecules with walls of the container c. weight of the gas d. composition of the gas

(ix)As we go up in the air:

a, atmospheric pressure increases b. atmospheric pressure decreases c. atmospheric pressure does not change d, atmospheric pressure becomes zero at the height of 1 km

(x)What instrument is used to measure height?

  1. hydrometer b. hygrometer c. altimeter   d. sphygmomanometer

ANSWERS: (i-c) (ii-c) (iii-a)(iv-b) (v-d) (vi-b) (vii-c) (viii-b) (ix-b) (x-c)

 

7.2 DEFINE THE FOLLOWING.

(i) Force

ANSWER: (i) Force                                                                                                             Push or pull which can move or press the things is called force. Example                                                                                                                                    ii Force of gravity which pull all things towards the centre of earth                its unit is Newton.

(ii) Area.                                                                                                                 Matter occupy space, that is the area of that matter. We can calculate area by multiplying length into Width.  Its unit is m2.

(iii) PRESSURE:  Force per unit area is called pressure its unit is Newton

P= &= =Nm-2

(iv) HYDRAULICS:  The branch of science which deals with the transmission of fluid pressure through pipes as a source of mechanical force is called hydraulics.

(v) PNEUMATICS: The branch of 4 science) which deals with the study and applications of pressurized gas to produce mechanical motion is called pneumatics.

 

7.3 GIVE BRIEF ANSWERS.

(i) Give the commonly used units of force.

ANSWER: Newton

(ii) Give the commonly used units of area.

ANSWER: m2 (meter square)

(iii) Give the commonly used units of pressure.

ANSWER:  The SI unit of pressure, the Pascal (Pa), for example, is one newton per square metre.

(iv) State Pascal’s law.

ANSWER: Pascal (Pa)

(v) Differentiate between hydrostatic pressure and atmospheric pressure.

ANSWER: The fluids enclosed in a vessel exert pressure which is transmitted equally in all directions.

(vi) In the figure shown below indicate the location where atmospheric pressure is expected to be lowest.

ANSWER:

 

7.4 EXPLAIN THE FOLLOWING.

(a) Water pressure (b) Atmospheric pressure (c) Aerosols

ANSWER: WATER  PRESSURE/HYDROSTATIC PRESSURE

Speed of water from a tank coming out of tap on ground floor is

greater than the speed of water coming out of a tap on upper story of

our house.

Water exerts pressure on the Walls of e the container. That is

called water pressure or hydrostatic pressure.

The speed of water coming out of the tap depends‘ upon the

height of the water tank above the ground floor.

That’s why water tanks are placed on the roof of the top floor.

(ii) ATMOSPHERIC PRESSURE

Our earth has a blanket of air around it. The earth’s gravity

pulls the  column down. Hence, the air has weight. The Weight of

the air column (force) per unit area on the earth is pressure-which is

termed as atmospheric pressure.

A Atmospheric pressure = Weight of air/area.

(iii) AEROSOLS: The products using-sol systems are called aerosols; Sol is mixture of suspended solid or liquid particles in a gas or ‘air. Different

types of aerosols are’ used for various purposes. They are used as

air freshener, insect repellents, hair sprays medicinal sprays (like

inhalers) etc.

7.5 DESCRIBE AN APPLICATION OF PASCAL’S LAW.
ANSWER: Pascal’s law is used in hydraulics. Hydraulics is the branch of

science which deals with the transmission of fluid pressure

through pipes as a source of mechanical force.

This system is lased to produce a large force with the help of a

small force.

7.6 DESCRIBE THE USE OF A PNEUMATIC SYSTEM IN DAILY LIFE.
ANSWER: PNEUMATICS

The branch of science which deals. with the study and

applications of pressurized gas to produce mechanical motion is called

pneumatics.

THE USE OF A PNEUMATIC SYSTEM IN DAILY LIFE

A Compressed air is widely used in various daily life activities and

in industries. Some 3c0mmon applications of compressed, air are

mentioned below:

1. Automobile tyres are inflated with compressed  air for smooth

running of vehicles.

2. Spray -guns use compressed air for spraying paint.

3. Air powered motors use compressed air  to work. Such motors are used at the places where electric motors are not

suitable for safety reasons.

4. Compressed air is used to operate air powered (pneumatic) tools like hammers drills etc.

5.The compressed air is also of used in airbrake system in heavy vehicles. When a brake pedal is pressed, the compressed air is released from the storage tank. This air pushes the brake pad against the moving wheel to stop its motion.

6. Most of the dentistry tools use com-pressed air for their working. It is safer for the patient.

 

CH:8 MEASUREMENT OF PHYSICAL QUANTITIES P:113-122

QUESTIONS

8.1 ENCIRCLE THE CORRECT OPTION.

(i) An electronic balance is used to measure:

  1. electric current b. length c. mass d. volume

(ii) SI unit of mass is:

  1. kilogram b. kilometer c. pound d. ounce

(iii) Which of the following liquids makes the men others?

  1. mercury b. Water c. alcohol d. petrol

(iv) Which of the following is SI unit of volume?

  1. m   b. ml    c. m   d. kg

(V) Amass of 2 kg is equal to:

  1. 1.000 g b. 2,000g c. 2,500 g d. 3,000 g

(vi) Which of the following relation is correct relation?

  1. 1min = 60h b. lm= 1.0O0cm c. 1mL = 1 cm3 d. 1min=30s

(vii) A length of 50 mm is equal to:

  1. 0.5m b. 0.05m c. 0.005m d. 0.0005m

(viii) 25 cm3 is equal to:

  1. 25 mL b, 2.5 mL c. 0.25 mL d. 250mL

(ix) One kilometre is equal to:

  1. 100m b. 500m c. l,000m d. l0,0O0m

(x) Pipettes are commonly used for:

  1. making solutions b. measuring the volume c. transferring a measured volume d. measuring mass

ANSWERS: (i-c) (ii-b) (iii-a)(iv-c) (v-b) (vi-c) (vii-c) (viii-a) (ix-c) (x-c)

8.2 MATCH THE WORDS OF COLUMN A WITH THOSE OF COLUMN B.

COLUMN A COLUMN B
      i.        Mass

ii.        Length

iii.        Volume

iv.        Time

v.        Unit

a)    Metre rule

b)    Flask

c)    Digital watch

d)   Standard quantity

e)     Balance

ANSWERS: (i-e) (ii-a) (iii-b) (iv-c) (v-d)

 

8.3 SHORT ANSWER QUESTIONS.

(i) Define a physical quantity,

ANSWER: The quantities which can be measured are called physical quantities.

Example: Length, mass, time, volume etc.

(ii) Define the term prefix.

ANSWER: PREFIXES

Prefixes are the multiples and submultiples of SI units. Prefixes are based on multiplying and dividing the units by powers of 10. The word added before the SI unit is known as prefixes.

(iii) What is A metre rule?

ANSWER: METRE RULE

A metre rule is one metre long graduated stick. It is usually used

to measure length of an object or distance between two points. A metre

rule is divided into l 100 equal parts, each part is equal to one centimere. Each centrimetre is further divided into 10 millimetres.

(iv) How many milliliters are there in one dm3?

ANSWER: 1000 ml

(v) How many seconds are there in one solar day?

ANSWER: 86400 S

 

8.4 DESCRIPTIVE QUESTIONS.

(i) What are SI units? Explain.

ANSWER: In 1980, the eleventh general conference of international committee on weights and measures recommended that all countries of the World should adapt at system of same kind of standard units. It is abbreviated as SI.

According to this system, the units of length, mass, time and

volume are: meter, kilogram, second and cubic meter, respectively.

Litre

A practical unit of volume is litre. 1 litre = 1000 milli litre = 1000 cubic centimeter.

(ii) Describe the importance of SI units.

ANSWER:

In our daily life, we often need to measure various physical

quantities. To measure a physical quantity, we compare it with

some standard quantity. For example, if we purchase some

sugar. we must know how much quantity of sugar we are talking

about. Thus, there is a need of some standard quantity for

measuring unknown quantity. This standard quantity is called unit.

(iii) The length of wooden rod IS 25.5 cm. What is this length in: a. millimeters? b. metres?

ANSWER: (a) 255 mm (b) m0.255

(iv) The mass of an iron plate is 1,950 g. What is this mass in kilograms?

ANSWER: 19,50,000

(v) Convert in minutes. A. 3600 s    b. 2h

ANSWER: (a) 3,600 s= 60 min (b) 2h=120 min

(vi) describe the use of measuring cylinder?

ANSWER:

 MEASURING CYLINDER

                   A measuring cylinder is used to measure the volume of a liquid.

It is made of glass or transparent plastic. It has a scale in millimeter (mL) or cubic centimeter (cm3) along its length.

That is Why, it is also called graduated cylinder.

Measuring cylinders of different capacities (from 100 mL to 2500 ml) are available in the school

laboratory. To measure the correct volume of a liquid, cylinder must be placed on horizontal.

surface and the eye should be kept on the  level with the bottom of the measuring cylinder.

(vii) write short note on measuring flask and pipette.

ANSWER:

           MEASURING FLASK :

Flasks are laboratory vessels (containers). They are made glass or plastic. Flasks are available in many shapes and sizes. Their sizes are specified by the volume they can hold. In school laboratory, these are usually available in the sizes of 50 mL; 100 mL,

250 mL, 500′ mL and 1000 ml. These are graduated l in the units of cubic centimeter (cc) or milliliters (mL)

Flasks are used for making solutions.

PIPETTES:

Pipettes are commonly used in Chemistry and Biology laboratory to transfer a measured volume of a liquid from one container to another.

Pipettes have several shapes and sizes. These are graduated to a specific mark. These are commonly available in the sizes of 10 mL to 25 mL. Pipettes are made by glass or plastic.

CH:9 SOURCES AND EFFECTS OF HEAT EN P:123-136

QUESTIONS

9.1 ENCIRCLE THE CORRECT OPTION.

(i) Which of the following is the biggest source of heat energy?

  1. Burning of fuels b. Electricity c, The Sun d. Food .

(ii)When an object is heated, the movement of its particle

  1. stops: b. is not disturbed c. decreases d. increases

(iii)Thermal expansion is not involved in:

  1. automatic fire alarm b. thermostat c. fixing metal tyres over the Wheels d. wooden stick

(iv)Activity of metallic ball and ring shows:

  1. solid objects expand on heating b. solid objects contract on healing c. solids change their nature on heating d, there is no effect of heat on solids

(v)What will happen to the inflated balloon as shown in the figure, if the burner is removed?

a, its volume will reduce b. its volume will increase P c, it will burst d. nothing will happen to it

(vi)The rise of liquid in the thermometer is due to:

a, evaporation . b. contraction c. expansion d. condensation

(vii)The contraction of the objects on cooling is due to the:

  1. reduction in size of the particles b, increase in size of the particles c. increase in inter particle distances d. decrease in inter particle distances

(viii)When ice melts and water reaches at 4 ”C, its density:

  1. increases b. decreases c. decreases 4 times d. remains the same

(ix)An empty steel container is sealed and heated, which of the following properties of the gas present in this container increases?

  1. mass b. pressure c. volume d. density

(x)The instrument which uses the property of expansion and contraction of liquids is:

a, barometer b. thermometer c. manometer d. speedometer

ANSWERS: (i-c) (ii-d) (iii-d)(iv-a) (v-a) (vi-c) (vii-d) (viii-b) (ix-c) (x-b)

 

9.2 GIVE SHORT ANSWERS.

(i) Write down the effects of heating and cooling on solids.

Ans. Solids expand on heating and contracts on cooling.

 

(ii) Write down the effects of heating and cooling on gases.

Ans: The volume of gases increases on heating and decreases on

Cooling.

 

(iii) Why is water not used instead of mercury p in thermometers?

 

Ans: The degree of expansion and contraction of mercury is much

higher than water. It can detect temperature change more

accurately.

 

(iv) Why one end of the iron girders is placed on rollers in

construction of bridges?

Ans: Because it can move forward be and backward during expansion

and contraction. So it can not damaged.

 

(v) Why gaps are left between ‘two sections 1 of a railway

track?

Ans: Because in summer due to hot weather, temperature of railway

sections increases and they expand and gaps fulfills. If gaps are

not present, then the railway track would crack in summer.

 

(vi) Why do hot air balloons rise up?

Ans.

Hot air is lighter than cool air so hot air balloon rises up.

 

(vii) Why do gases expand faster than liquids and solids?

Ans: Gases expand faster than liquids and solids because

intermolecular forces are less due to spaces between molecules.

So attraction among molecules less for this reason gas expands

faster.

(viii) When a vessel containing a liquid is heated, the level of

liquid initially falls and then rises up. Why does it happen so?

Ans: Liquids molecules rises from the bases on heating towards

surface. The surface molecules come down to fulfill the space of

the molecules, so Water level, lowers. But after some time, all

liquids become hot and all molecules rises, so liquids level rises

on heating.

 

 9.3 DESCRIPTIVE QUESTIONS.

(i) What is meant by thermal expansion? Explain expansion of solids with the help of an experiment.

ANSWER: THERMAL EXPANSION & CONTRACTION OF SOLIDS

The material objects are made up of tiny particle; atoms

molecules: In solid objects these particles are strongly packed

each other. The motion of particles in solids is vibratory only, i.e.

move to and fro about their fixed positions. When solids are heated,

vibratory motion of their particles (atoms and molecules) becomes

and they begin to push each other further apart. This results

expansion of solids. Similarly, when solids are cooled, particles

down and solids contract.

EXPERIMENT.

Material Required

Metal bob and ring apparatus (metallic sphere, ring, chain)

stand, burner or spirit lamp

  • Take a metallic sphere which can pass easily through a ring as

shown in figure (a).

  • Remove the sphere out of the ring with the help of the chain attached to it.
  • Heat the sphere to a high temperature and put it on the ring in order to pass it through the ring as shown in figure (b).
  • Does it pass through the ring after heating?
  • If not, why does it happen so?
  • Let the sphere cool at room temperature and observe Whether it

passes through the ring or not.

(ii) Demonstrate how a bimetallic strip works in a thermostat.

ANSWER: FIXING A METAL TYRE OVER THE WHEEL

The metal tyres which are ‘fixed over the wooden Wheels of the

carts are slightly smaller than the wheels when they are cold. On

heating, the metal tyre expands and its diameter increases. Then hot

tyre can easily befitted onto the wheel. On cooling, the metal tyre

contracts and fits over the Wheel tightly.

(iii) Explain the peculiar behavior of water during contraction and expansion.

BEHAVIOR OF WATER DURING CONTRACTION

This method is mostly used to fit in the axle of train Wheels. In

this method, contraction is used instead of thermal expansion.

The diameter of the axle is slightly larger than the hub of the

metal Wheel. The axle is placed in liquid nitrogen which is below -150

C temperature. The axle cools and contracts. It is then inserted into

the hub of the Wheel and is allowed to come at room temperature. At

room temperature, axle expands and fits into the wheel tightly.  

 ANSWER:

(iv) Explain the damages which are caused by expansion or contraction by giving two examples.

  ANSWER: In our daily life, we pay special attention to deal With thermal

expansion and contraction of solids in various i construction

projects. In order to avoid the harmful effects of thermal expansion and contraction of solids, the techniques used in

different projects are as follows:

  1. EXPANSION GAPS IN CONCRETE ROADS

In hot summer, the concrete used to build roads expands. If no

space is provided for its expansion, the road surface cracks. To avoid

such damage, small gaps are left after every few metres in the

construction of concrete roads or footpaths.

2.RAILWAY TRACKS

Two sections of a railway track are not welded together. Instead

they are, laid with gaps between them. This allows expansion and contraction of rails during summer and winter seasons. If there are no gaps in the sections of railway tracks, they may de- shape due to expansion in summer.

(v) Describe the effects of expansion and contraction of solids.

ANSWER: EXPERIMENT.

Material Required

Metal bob and ring apparatus (metallic sphere, ring, chain)

stand, burner or spirit lamp

  • Take a metallic sphere which can pass easily through a ring as

shown in figure (a).

  • Remove the sphere out of the ring with the help of the chain attached to it.
  • Heat the sphere to a high temperature and put it on the ring in order to pass it through the ring as shown in figure (b).
  • Does it pass through the ring after heating?
  • If not, why does it happen so?
  • Let the sphere cool at room temperature and observe Whether it

passes through the ring or not.

(vi) Explain the expansion of liquids with the help of an experiment.

ANSWER: THERMAL EXPANSION AND CONTRACTION OF LIQUIDS

EXPERIMENT:

Apparatus/Material required:

Round bottomed glass flask, cork or rubber plug which can be

fitted at the mouth of flask, narrow glass tube, coloured water

PROCEDURE:

  • Take a round bottomed glass flask and fill it fully with coloured

water.

  • Pass a glass tube which is open at its both ends through a cork or

rubber plug and fit the rubber plug into the mouth of the flask

tightly as shown in the figure.

  • Water will rise up in the glass tube to a small height.
  • Note the level of the coloured water in the glass tube.
  • Now heat the flask over a burner or spirit lamp.
  • Observe what happens to the level of the coloured water in the

Glass tube.

  • Record what do you observe?
  • Now switch off the burner and let the hot Water to

cool at room temperature.

  • Note the level of the water again.
  • What conclusion do you draw from this activity?
  • As you start heating the water, you will notice that the level of water in the tube first falls and then begins to rise up.

Why does it happen so?

On heating, liquids molecules at the bottom rises and the

molecules from the upper surface come down to fulfill the space of

bottom molecule. After it the liquids heated and then its level.

 

(vii) Describe a simple experiment to study the thermal expansion of gases.

 ANSWER: APPLICATIONS OF EXPANSION AND CONTRACTION OF SOLIDS

Thermal expansion and contraction are used for different

purposes. A few examples are:

RIVETING

A rivet is a small, cylindrical and smooth shaft whose one end is swollen (called head) while the other end is flat (called  buck-tail). Hot rivets are used to join the metal plates. The process in which two metal plates are joined together by means of rivets is called riveting. For joining the two steel plates; they are placed one above the other and holes are drilled through them. The rivet is heated to make it red hot and is inserted in the holes of the plates (Figure 9.9-a). The ends of the rivet are then hammered into a round shape (Figure 9.9-ab). When the rivet cools and contracts, it firmly grips the plate together.

 

CH:10 LENSES P:137-148

QUESTIONS

10.1 ENCIRCLE THE CORRECT OPTION.

(i) A ray parallel to principal axis, after refraction from convex lens:

  1. does not bend b. passes through c. passes through d. passes through the middle of F and C

(ii) The centre of a lens is called:

  1. optical centre b. centre of curvature c. principal focus d. principal axis

(iii) The location of image of an object lying beyond 2F in front of a convex lens is

  1. between F and 2F b. beyond 2F c. at F d. at 2F

(iv) The image of an object placed at C in front of a convex lens is formed:

  1. at F b. between F and C c. at C d. beyond C

(v) The image formed by a concave lens is:

a, virtual b. real c. inverted d. larger

(vi) The point through which a ray of light passes without changing its path is the:

  1. centre of curvature b. optical centre c. middle point of F and C d, principal focus

(vii) Pupil is made smaller or larger by:

  1. ciliary muscles b. cornea c. iris d. retina

(viii) In human eye, image is formed on:

  1. cornea b. pupil c. iris d. retina

(ix) To obtain sharp image in a camera:

  1. lens is moved back and forth b. film is moved back and forth c. both the lens and the film are moved d. neither lens nor film is moved

ANSWERS: (i-b) (ii-a) (iii-d)(iv-d) (v-a) (vi-b) (vii-c) (viii-d) (ix-a)

 

10.2 GIVE SHORT ANSWERS.

(i) Describe the paths of three rays which form image after passing through a convex lens.

ANSWERS: IMAGE FORMATION BY THE LENSES

                    Where and how an image is formed by pa lens, it can ‘be known by drawing a ray diagram. A ray diagram a drawing showing the ‘path of light rays. Therefore, the location and nature of image formed by a lens can be found very easily through a ray diagram. In. this method, two or three light ray shemerging from an object and passing through a lens are used. The image of the object is formed at the point where all their fracted trays meet after passing through the lens. In a ray diagram, light rays are represented by straight lines with arrow heads.

The arrow heads show the direction of light gray. The following properties are used in drawing the ray diagrams:

  1. When a ray parallel to the principal axis: After refraction
  2. V When a ray incident on the convex lens: After passing from a convex lens passes through its principal focus (F). In case of concave lens, the refracted ray appears to come from the principal focus Object Object

F s F V. Principal axis F

Convex lens W Concave lens through its principal focus (F) becomes parallel to the principal

axis after refraction. In case of a concave lens, the ray pointing towards the principal focus becomes parallel to the principal axis.

  1. When a ray passing through the optical centre of the lens goes straight without changing its direction.

(ii) Write the names of three instruments in which convex lens is used.

ANSWER: camera, telescope and microscope

(iii) Define focal length.

Ans. Distance between optical centre (O) and focal point (F) of the

lense is “called focal length.

(iv) Can image be obtained on the screen by a concave lens?

‘ Explain your answer briefly.

Ans. It diverge the rays so they can not meet at any point. Thus, so

in image cannot be formed.

(v) Q What is a ray diagram?

Ans. Ray diagram is a drawing showing the path of light ray.

 

(vi) How is the focal length affected when the lens of eye becomes thicker?

Ans. Focal length of thick convex lens is shorter than that of thin lens

l due to thickness of lens distance will be decreased.

(vii) Upon what factor does the amount of light entering in a

camera depend?

Ans. Size of aperture.

(viii) How long our eye takes to acquire dark adaption at its maximum?

Ans. Only some seconds.

(ix) Define short sightedness and long-sightedness

Ans.

  1. SHORT SIGHTEDNESS

Distant object is formed in front of the retina and not at the retina itself.

This defect is also known as myopia and is corrected by using

concave lens of suitable focal length. The concave lens diverges the

light rays before they enter the eye and hence, the rays are refracted

by the eye lens again to meet at the retina.

  1. LONG-SIGHTEDNESS

A person having this defect can see distant objects clearly but

near objects appear blurred. This defect is caused when the eye lens

becomes thin or the eyeball becomes too short. Due to this effect, the

image of the near object is formed beyond the retina. That is why, the

near object appears blurred in long-sightedness. This defect is known

as hyperopia and is corrected by using suitable convex lens. The convex

lens converges light rays before they enter the eye} After entering the

eye, they are further bent by the eye lens to meet at the retina.

 

10.3 WHAT IS A LENS? EXPLAIN THE DIFFERENCE BETWEEN CONVEX AND CONCAVE LENSES?
ANSWER: LENSES

Lenses are Widely used in our life; Many eyesight defects are

corrected by the use of lenses. Lenses are commonly used in spectacles;

cameras, microscopes, telescopes binoculars, projectors and many other

instruments for different purposes. Contact lenses are also becoming

very popular these days. These can be placed in eyes and removed

easily when needed.

DIFFERENCE BETWEEN CONVEX & CONCAVE LENSES

1-    The concave lenses curve inward and bend light rays outward, causing the light rays to diverge.

2-    They are used in the treatment of myopia, or near-sightedness. Because light is focused in front of the retina in a near-sighted individual, the concave lenses help by allowing the light to bend and focus further back, thus promoting clearer vision at a distance.

3-    Concave lens are used in movie projectors to cause the image to spread.

4-     The lens of a normal eye is a double convex lens.

5-     Convex lenses round outward and cause light rays to converge.

6-    Convex lenses are beneficial in treating presbyopia, or far-sightedness. In a far-sighted person, the light is focused behind the retina.

7-    The convex lens corrects this problem and allows the person to see clearly up close. Convex lenses are also found in magnifying glasses, binoculars, telescopes and cameras.

8-    Certain telescopes and microscopes use concave mirrors as well as convex lenses.

9-     The convex lens of a human eye actually focuses the image upside down on the retina, but the brain interprets it the right way.

10.4 EXPLAIN THROUGH RAY DIAGRAM WHERE THE IMAGES WOULD BE FORMED BY CONVEX LENS FOR DIFFERENT DISTANCES OF OBJECT, ALSO DISCUSS THE NATURE OF IMAGES.
ANSWER: IMAGE FORMATION BY THE LENSES

Where and how an image is formed by a lens, it can be known by

drawing a ray diagram. A ray diagram is a drawing showing the path

of light rays. Therefore, the location and nature of image formed by a

lens can be found very easily through a ray diagram. In this method,

two or three light ray semerging from an object and passing through a

lens are used. The image of the object is formed at the point where all

the refracted rays meet after passing’ through the lens. In a ray

diagram, light rays are represented by straight lines with arrow heads.

The arrow heads show the direction of light ray. The following

properties are used in drawing the ray diagrams:

 

When a ray parallel to the principal axis: After refraction

from a, convex lens passes through its principal focus (F). In ease

of  concave lens, the refracted ray appears to come from the principal focus (F).

 

When a ray incident on the convex lens: After passing

through its principal focus (F) becomes parallel to the principal

axis after refraction. In case of a concave lens, the ray pointing

towards the principal focus becomes parallel to the principal

 

When a ray passing through the optical centre of the lens

goes straight without changing its direction.

10.5 WHAT IS A REAL AND VIRTUAL IMAGE? WHY IS REAL IMAGE NOT FMED BY CONCAVE LENS? EXPLAIN YOUR ANSWER BY RAY DIAGRAM.
ANSWER:

REAL IMAGE

            The image which can be saved on screen is called real image.

Virtual Image

The image which cannot be saved on screen is called virtual

image.

IMAGE OF CONCAVE LENSE

            Concave lense diverge the light rays. S0 they cannot meet with

each other at any point. Thus, so we cannot take image on screen.

Concave lense image is always virtual.

10.6 EXPLAIN HOW EYES GET USED TO DARKNESS ATIER SOMETIME.
ANSWER:

We use lenses of different focal lengths for different purposes

For the correct use of a lens, its focal length should be known

Let us perform a simple activity to find the focal length.

10.7 HOW DO CAMERA AND HUMAN EYE RESEMBLE WITH EACH OTHER? WHAT IS THE DIFFERENCE IN THEIR ACTIONS?
ANSWER:

In a camera, lens is moved back and forth to focus the image on

the film, but the eye lens does not move. Instead, the ciliary

muscles make the lens thick or thin due to which its focal length

changes. When you are looking at distant object, the ciliary

muscles are in relaxed position and the image is formed on the

retina. To look at something closer to the eye, these muscles

make the lens thicker. This makes its focal length shorter and

the image is again formed on the ‘retina instead of forming at a

point beyond it.

 

CH: 11 ELECTRICITY IN ACTION149-159

QUESTIONS

11.1 ENCIRCLE THE CORRECT OPTIONS

(i) Which power plant is almost free from environmental pollution problems?

  1. Thermal power plant b. Nuclear power plant c. Hydro power plant d, Solar power plant

(ii) Which is the cheapest source of energy to produce electricity?

  1. hydel b. atomic c. solar d. thermal

(iii) Electronics is the branch of physics that concerns with the behavior and control of motion of:

  1. protons b. electrons c. neutrons d. atoms

(iv) Which of the following is an input device?

  1. mouse b. monitor c, printer d. hard disc

(v) Which of the following is an output device?

  1. printer b. mouse c. scanner d. hard disc

(vi) The component which converts A.C into D.C is called:

  1. amplifier b, semiconductor diode c. transformer d. semiconductor

(vii)Which of the following is a processor?

  1. mouse b. tape recorder c, keyboard d. monitor

ANSWERS: (i-c) (ii-c) (iii-b)(iv-a) (v-a) (vi-b)(vii-b)

 

11.2 SHORT ANSWERS

 (i) State the (principle of power generator.

Ans: In the power plant generator, a coil is kept stationary While a

magnet is turned inside the coil. The stationary coil is called

stator While the moving magnet is called rotor.

 

(ii) What are input devices? Give at least three examples.

Ans: Any device that changes non electronical energy into electrical

energy in an electronic system is” called an input device.

Example

Microphone, keyboard, mouse and scanner.

 

(iii) What are output devices? Give at least three examples.

Ans: An output device is a device that converts electrical energy into

other forms of energy. Example, monitor, printer, speakers.

 

(iv) What is the difference between A. C. and D.C?

A.C DC
The current which is not

Unidirectional its direction

change its direction again and

called A.C current.

The current which is unidirectional and does not change

changes again and again is

again is called direct current.

 

(v) Name some basic components of electronic system.

Ans: Basic components of electronic. systems are resistor,

semiconductor diodes, transistors,-silicon ‘chips and integrated circuits.

 

(vi) What is the function of a solar panel?

Ans: Solar panels with the interconnection of photovoltaic cells are

used to produce electricity in the brighter sunlight.

 

11.3 Sketch an electric generator and its important parts.

pic

 

 

 

11.4 Describe the working of power generator.

Ans. Electricity can also be produced by some mechanical ways. Just

 as We can make magnets from electricity, we can also use

magnets to make electricity. We know that if a magnet is moved

quickly through a coil of copper wire, electrons move in the Wire

and thus electricity is produced. Electricity can also be produced

by rotating a coil between the opposite poles of a magnet. The

mechanical system to produce electricity, in this way is called

electric generator or dynamo. Thus, due to relative f motion

between a coil and magnet, electric current starts to flow through

the coil which can be connected to an external circuit.

          The current produced by electric generators is not unidirectional.

Its. direction changes again and again after an equal interval of time.

Such a current is called alternating-current (A.C). For the production

of electricity of higher voltage, a generator should have:

  • stronger magnets
  • more turns in its coil
  • quick relative motion between the magnet and coil

 

11.5 DISCUSS THE PROBLEMS INVOLVED IN:

(I) HYDEL POWER GENERATION

(II) THERMAL POWER GENERATION

(III) SOLAR POWER GENERATION

Ans. Many typeslof problems are involved in generation of electricity.

 Some of them are described below:

(I) PROBLEMSEIN HYDEL POWER GENERATION

            Hydroelectric power is one of the ‘traditional methods of

production of electricity; Despite the ‘fact that it is the cheapest way of

getting electricity, some problems are therein this method. The people

living in these areas where the dams are to be constructed, are shifted

to some other places. In winter, its capacity decreases due to shortage

of water. Moreover, water level near a-dam rises, due to which water

logging occurs and the land becomes uncultivable.

(II) PROBLEMS IN THERMAL POWER GENERATION

               Electricity production by using thermal energy involves burning

of fossil fuels (oil, gas, coal). These are non-renewable energy sources.

That is Why the existing reserves of fossil fuels are running short day

by day and their prices are shooting up. Moreover, fossil fuels release

smoke and other harmful gases in atmosphere.

(III) PROBLEMS IN SOLAR POWER GENERATION

           Solar power is becoming very popular these days.. Solar energy is

renewable source of energy and is available to everyone,‘ free of cost.

Production of electricity by using solar energy is safe and causes no

pollution, but still has certain problems. The major problem is the high

initial cost of solar panels and storage batteries.

 

11.6 WHAT IS AN ELECTRONIC SYSTEM? DRAW THE BLOCK DIAGRAM TO

SHOW THE FUNCTIONS OF DIFFERENT STAGES OF TELEVISION.

Ans. The branch of physics that concerns with the behaviour and

control of motion of electrons is called electronics. Electronic  systems use short pulses of electric current to carry information in the form of signals. Later on, these signals can be changed into sounds, pictures or other information.

           A well-known example of an electronic system is television.

Without going through the details of internal working of its different parts, we can describe their functions by a block diagram of the system

as shown in Figure.

          The following steps will explain how the system operates:

A camera converts picture and a microphone converts sound into electronical signals at the TV station.

These signals are mixed with carrier waves and are transmitted through transmitter antenna or cable.

Signals are received-by TV in the form of a weak alternating current.

These signals are amplified by the ‘amplifiers already installed in the TV.

The circuits inside the TV separate video and audio signals.

Video signals go to the picture tube that displays motion picture on the screen.

Audio signals go to the speaker that converts them back into Sound.

 

CH:12 EXPLORING SPACE160-169

QUESTIONS

12.1. ENCIRCLE THE CORRECT OPTION.

  1. An instrument that helps for seeing heavenly objects:
  2. Microscope b. Telescope c. Spectroscope d. kaleidoscope

ii, Telescopes on the Earth suffer from the fact that the light coming from the stars has to pass through:

  1. space b, water c. air d. sea

iii. A vehicle, designed to carry satellite in outer space is:

a, Rocket b. Air bus c. Air jet d. Spacecraft

  1. Spectroscope is an instrument used to examine the wavelengths of:
  2. light waves b. water waves c. air waves d. sound waves

v, Physical exploration of space is conducted both by human spaceflights and:

  1. telescope b. robotic spacecraft b. rocket d. spectroscope

ANSWERS: (i-c) (ii-c) (iii-d)(iv-a) (v-b)

 

12.2 GIVE SHORT ANSWERS.

  1. How does reflecting telescope differ from refracting telescope?

ANSWER: Reflecting telescope has concave mirror but refracting telescope

has two lenses.

  1. What are rockets?

ANSWER: Rockets are the means of transporting spacecrafts, space shuttles and space is stations into the space.

iii. What is the advantage of putting a telescope in space?

ANSWER: It has taken clear pictures of galaxies

  1. What is remote sensing?

 ANSWER: Special sensors for monitoring the physical health of astronaut is the remote sensing.

  1. For what GPS stands for?

ANSWER: GPS stands for Global positioning system.

 

12.3 DESCRIBE THE BENEFITS GENERATED BY TECHNOLOGY OF SPACE EXPLORATION.
ANSWER:

 SPACE EXPLORATION

            Scientific study of the space using specially developed technology is called space exploration. Common objectives “for exploring space include advancing scientific research, ensuring the future survival of humanity, and developing military and strategic advantages against

other countries.

BENEFITS OF SPACE EXPLORATION

          A Special technologies developed for space are now being used on the Earth to develop economy and improve quality of life. A few examples are as follows:

HEALTH AND MEDICINE

1. In the field of health and medicines, space exploration has enabled man to develop medical devices such as WARP 10 and hand-held high intensity LED unit etc.

These machines are used for getting relief in muscle and joint pains, arthritis, and muscles spasms etc.

2. The  infrared thermometer has been developed to measure the temperature of body Without contact

3. Kidney dialysis machines and mini cameras for taking the photographs of internal organ systems of human body have been developed using the research output during space exploration.

4. The materials used to keep our homes warm are based on the technology used for insulating the space stations.

GLOBAL NAVIGATION

1. Geostationary Orbits and Global Positioning System (GPS) use the network of satellites orbiting the Earth to facilitate communication  and essential navigation. This system helps our telephone receivers and mobile phones to catch Signals from the satellites moving around the globe.

2. The travellers can use this system not only for knowing where they are  travelling but  also for selecting best GPS satellites around the Earth route to their destination. Aeroplane pilots, sailors of the boats or desert hikers also use the GPS in mobile phones to find their positions and get information about the surroundings.

WEATHER FORECAST AND PREDICTION OF NATURAL CALAMITIES

                The accurate and reliable weather reports on hourly basis are possible because of the Weather satellites in the space. These satellites have also made, it easy to predict natural calamities such as floods, storms tornadoes and hurricanes.

ADVANCED ELECTRONICS AND COMPUTERS

The field of electronics and computer systems were developed mainly to facilitate space exploration. Satellites have linked the world through a network of electronic devices and computers.

This has reduced the communication gaps and promoted the sharing of technologies among the countries: over the world.

LOCATING MINERALS, FOSSIL FUELS AND WATER RESERVES

4. Deeply buried precious ores of minerals, a fossil fuels (coal, petroleum and natural gas) and underground water reserves can be located with the help of satellites.

This study is known as remote sensing.

12.4 EXPLAIN HOW DO ASTRONAUTS SURVIVE AND WORK IN SPACE.
ANSWER:

        For living in space, astronauts need basic necessities (air, food, Water, shelter and Warmth) for survival, and a suitable compartment for personal comforts on the spacecraft. For this purpose, large space stations have been built in the space. Each space station consists of two, main sections:

(i)            Pressurized section, in which scientists work without needing space suits,

(ii)          Open-to-Space section on which equipment is mounted for

observing the Earth and they sky. Unprotected human body cannot survive more than a few minutes in space.

SPACESUIT

As liquid boils at lower temperature at lower pressure, the Water in human body can begin to boil at low pressure resulting immediate

death. The astronauts Wear a specially designed suit called space suit to protect from such hazards when they go out into  space.

FOR BREATHING IN SPACE, they carry air tanks with them that, contain.

Astronaut wearing space suit pressurized oxygen and nitrogen. Their suits circulate the air to their helmets and throughout the suit so that they can breathe.

Special foods are prepared and packaged for easier

transportation and a variety of tastes for the astronauts.

12.5 DESCRIBE THE TECHNOLOGICAL TOOLS USED IN SPACE EXPLORATION.
ANSWER:

SPECTROSCOPES 

               A spectroscope is an instrument which is used to examine different Wavelengths (colours) of a light. It consists of a series of prisms that splits White light into different colours. The set of different colours obtained in this Way, is called spectrum. Spectroscope also measures the wavelengths of different colours of the spectrum. The wavelengths of light coming from the stars help the scientists know

about the elements and compounds present in the stars. Spectroscopes are mostly attached with the telescopes.

 SPACECRAFT

               Spacecraft is at vehicle designed to travel in space It is used for

different purposes like communication, Earth s observation,

meteorology, navigation, planetary exploration, transportation of

humans and cargo in space.

ROBOTIC SPACECRAFTS are sent into space for the collection of data about space, planets and other heavenly ‘bodies such. as asteroids. A robotic spacecraft is controlled from a centre on the earth.

 VOYAGER LAND

Voyager  were two robotic spacecrafts which were used for collecting data about planets, Mars and Jupiter.

 A Manned spacecrafts  carry humans and equipment to space

These spacecraft are larger, and have specially built compartments

which have the facilities necessary for human survival such as oxygen,

pressurized cabins, food, Water and specially built bathrooms They

also have special structure to protect from dangerous radiations which

are very intense in space.

SPACE STATIONS

For very long stay in space or for space, large space crafts called space stations are used. A space station is built in. space bye carrying its many small parts to space and then assembling them there. It has more facilities. For prolonged living in space. It may Space station have television for entertainment, bags for sleeping, exercise machines and kitchen for fresh food. One important part of a space is the scientific laboratory Where astronauts perform such experiments that cannot be done on the earth because of its gravity. Nowadays, a large space station orbits the Earth.

Russians, Americans and other scientists jointly Work in this

space station. This is called international space station.

12.6 DESCRIBE FOUR PROBLEMS CREATED FROM SPACE EXPLORATION AND THEIR SOLUTIONS.
ANSWER:

           Space sickness, effects of weightlessness, conditions resulting

from exposure to radiation and many unwanted side effects are the problems created during the stay in space. Pollution caused by burning of rocket fuel and disposal of rocket parts etc. is one of the major problems created by space exploration.

Hazards for the space crew on missions are also the main problems. Many deaths have resulted during the manned spaceflights Space scientists and engineers need continuous work on the safety issues and design safe programmes.

Skylab fell from its orbit to the Earth in 1979. These types of

incidences could be dangerous for population.

Space programmes are very costly. These are causing economic burden on common man. Involvement of private sector in missions could be possible solution.

12.7 WRITE SHORT NOTES ON THE FOLLOWING:

i. Hubble Space Telescope ii. Space Probes iii. Space Stations

ANSWER:

(i) HUBBLE SPACE TELESCOPE

         Hubble space telescope is the first space-based reflecting  telescope launched in 1990. It orbits around the Earth at a height of 600 km and works round the clock. It has taken clear pictures of galaxies, billions of kilometers away.

(ii) SPACE PROBES

A probe is a spacecraft that travels through space to collect science information. Probes do not have astronauts. Probes send data back to Earth for scientists to study.

or

A space probe is a robotic spacecraft that leaves Earth orbit and explores space. It may approach the Moon; enter interplanetary spacefly byorbit, or land on other planetary bodies; or approach interstellar space.

(iii) SPACE STATIONS

For very long stay in space qr for performing experiments in space, large space crafts called space stations are used. A space station is built in. space bye carrying its many small parts to space and then assembling them there. It has more facilities for prolonged living in space. It may Space station have television for entertainment, bags for sleeping, exercise machines and kitchen  fresh food. ‘One important part of a space is the scientific laboratory where astronauts perform such

experiments that cannot be! done on the earth because of its

gravity. Nowadays, a large space station orbits the Earth.

Russians, Americans and other scientists jointly work in this

space station. This is called international space station.

 

——————————————–END————————————

 
It's only fair to share...Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInPrint this pageEmail this to someone
Loading Facebook Comments ...

Leave a Reply

Your email address will not be published. Required fields are marked *