worksheet on combustion

CBSE

 Worksheet

 Class–VIII Science (Combustion and Flame) 

1. Water should not be used as extinguishing agent for fires caused by :- 
a. oil b. electricity c. both a & b d. burning of wood
 2. A fire extinguisher works on following principle/s :-
 a. removing combustible substance
 b. cooling the burning substance below ignition temperature 
  c. cutting off supply of air
 d. both b & c 
3. The dark zone of a candle flame is :- 
a. region around the wick
 b. base close to wick
 c. middle region of flame 
d. outer region of flame.
 4. Incompletely burnt fuel releases a very poisonous gas that can be fatal if inhaled :- 
a. carbon dioxide b. ozone c. carbon monoxide d. water gas 
5. Match the column :-

 a. Carbon dioxide                i) also called gobar gas 
 b. Oxygen                            ii) highest calorific value
 c. Hydrogen                       iii) gas essential for burning 
d. Biogas                             iv) non pollutant vehicular fuel 
e. CNG                                 v) used in fire extinguisher 
 6. State whether the following statements are true or false :-
 a. If ignition temperature is higher than room temperature, the fuel is considered good. 
b. Combustion is an oxidation process.
 c. If supply of oxygen is insufficient during combustion, carbon dioxide is formed instead of carbon monoxide. 
d. Any combustion reaction not accompanied by flame is known as burning. 
e. Body fuel like butter gives us more energy than others. 
7. What is SPM? Which type of pollution it might cause? 
8. Deforestation and excess burning of fossil fuels is leading to a global problem. Explain it. 
9. Pick the odd word out of the following: 
 LPG, wax, kerosene, charcoal, bunsen burner. 
10. Write the correct words by putting letters in correct sequence-
 i) panetsouson                          ii) riversoco 

Separation of substances

CLASS 6

NOTES

 A pure substance  has particles of one kind only for example distilled water contains particles of water.
  Mixture is a combination of two or more types of particles for example air has particles of oxygen , nitrogen , carbon dioxide ,water in the form of vapour . Dust and smoke particles are also present in air. 
The substances present in a mixture are called its components so oxygen, nitrogen, carbon dioxide, water in the form of vapour, dust and smoke particles are the components of air.

TYPES OF MIXTURES
HETEROGENEOUS AND HOMOGENEOUS MIXTURES.

A   HETEROGENEOUS mixture is a combination of two or more pure substances in which the original substances retain their chemical properties. For example
oil and water, sand and water, fruit salad. 

A  HOMOGENEOUS mixture  has uniform composition and properties throughout. For example, 
air is a homogeneous mixture of gases.  

 WHY DO WE NEED TO SEPARATE MIXTURES?
 Most of the substances around us are mixtures and a very few are pure substances. 
Separation of mixtures becomes necessary for several reasons mentioned below: 
1. TO OBTAIN USEFUL COMPONENTS Petroleum is refined to separate petrol, Kerosene, diesel and Vaseline etc as petroleum cannot be used as such and metals are extracted from their natural forms which are mixtures before they can be used. 
2. TO GET PURE SUBSTANCE FROM A MIXTURE Distilled water can be obtained from any water sample by simple distillation. 3. TO REMOVE HARMFUL COMPONENTS Sometimes rice or pulses might contain small stones which can be harmful for us.

 HANDPICKING This method can be used when the components of the mixture differ in size, shape or colour and when the component to be separated from the mixture is present in small quantity. In this method the component of the mixture which is bigger in size is removed from the mixture by hand. For example stones can be removed from rice by handpicking. 

 WINNOWING When the components of a mixture have difference in their weight, for example one component is heavier than the other,the mixture is made to fall from a height and the component of the mixture which is heavier will fall down almost vertically and the lighter component will be blown away by the wind and form a heap at a distance.
 For example chaff is separated from the grains by winnowing as chaff is lighter than the grains. 

SIEVING This method is used when a mixture has particles of different sizes and a sieve can be used to separate them, the pores in the sieve will allow the smaller particles of the mixture to pass through them and retain the particles which are bigger in size. This method can be commonly used at home separate bran from the wheat flour. 

 SEPARATING INSOLUBLE SOLDS FROM LIQUIDS
 Solids like chalk powder, sand and dust particles are insoluble in water. Particles of such solids can be separated from their solutions by using one of the following methods:
  Sedimentation and decantation
  Filtration 
 Loading 
Sedimentation and Decantation: Insoluble substances like sand which are heavier than water settle down on their own. due to gravity. These particles which settle down form the sediment. This process is called sedimentation .The clear liquid is carefully poured into another container without disturbing the sediment .This process of pouring the liquid is known as decantation 
Filtration is commonly used for the separation of insoluble solids from their solutions by using a filter through which only the liquid can pass. 
Correct these statements : 
 A mixture of oil and water cannot be separated. 
 Distillation should be used to separate a mixture of sand and water. 
 Loading slows down sedimentation. 
 Distillate and filtrate are the same. 

 SEPARATING SOLUBLE SOLIDS FROM THEIR SOLUTIONS : The soluble solids can be separated from liquids by using the following methods : – 
 Evaporation.
  Distillation
 Evaporation: In this method the mixture of a soluble solid in a liquid is heated and the liquid evaporates leaving behind the solid .This method is commonly used to separate a soluble substance from its solution by heating the mixture. Salt is separated from sea water by this method. 
Distillation: Another method of separating a soluble solid from a solution is distillation. The solution is heated so that the liquid evaporates and their vapours are then cooled till they condense to give the pure liquid.
 Distilled water used in laboratories is obtained using this method. A special apparatus has to be used for carrying out distillation. The clear liquid thus obtained is known as distillate.

Separation Of A Mixture Of Two Liquid
 The two liquids don’t mix even on stirring. Such liquids which are insoluble in one another are called immiscible liquids. 
These liquids can be separated by using a separating funnel.

Magnetic Separation 
A magnet can be used to separate iron pieces which are attracted by a magnet from the other substance which is not attracted by the magnet like sand .The iron pieces sticks to the magnet but sand does not. 
SOLUTIONS AND SOLUBILITY 
A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. 
Generally the component of the mixture which is larger in amount is called solvent and the one which is smaller in amount is called solute.  

CLASS 6 ASSIGNMENT SEPARATION OF SUBSTANCES

SEPARATION OF MIXTURES

CLASS 6

ASSIGNMENT

MULTIPLE CHOICE QUESTIONS

 1. Paheli bought some vegetables such as french beans, lady’s finger, green chillies, brinjals and potatoes all mixed in a bag. Which of the following methods of separation would be most appropriate for her to separate them?

 (a) Winnowing (b) Sieving (c) Threshing (d) Hand picking

 2. Boojho’s grandmother is suffering from diabetes. Her doctor advised her to take ‘Lassi’ with less fat content. Which of the following methods would be most appropriate for Boojho to prepare it? 

(a) Filtration (b) Decantation (c) Churning (d) Winnowing 

3. Which of the following mixtures would you be able to separate using the method of filtration? 

(a) Oil in water (b) Cornflakes in milk (c) Salt in water (d) Sugar in milk 

4. Which amongst the following methods would be most appropriate to separate grains from bundles of stalks?

 (a) Hand picking (b) Winnowing (c) Sieving (d) Threshing 

5. Four mixtures are given below 

(i) Kidney beans and chick peas (ii) Pulses and rice

 (iii) Rice flakes and corn            (iv) Potato wafers and biscuits 

Which of these can be separated by the method of winnowing?

 (a) (i) and (ii)

 (b) (ii) and (iii)

 (c) (i) and (iii)

 (d) (iii) and (iv) 

6. While preparing chapatis, Paheli found that the flour to be used was mixed with wheat grains. Which out of the following is the most suitable method to separate the grains from the flour?

 (a) Threshing (b) Sieving (c) Winnowing (d) Filtration 

7. You might have observed the preparation of ghee from butter and cream at home. Which method(s) can be used to separate ghee from the residue?

 (i) Evaporation (ii) Decantation  (iii) Filtration (iv) Churning Which of the following combination is the correct answer? 

(a) (i) and (ii)

 (b) (ii) and (iii) 

(c) (ii) and (iv) 

(d) (iv) only 

8. In an activity, a teacher dissolved a small amount of solid copper sulphate in a tumbler half filled with water. Which method would you use to get back solid copper sulphate from the solution?

 (a) Decantation                    (b) Evaporation 

(c) Sedimentation                 (d) Condensation

 9. During summer, Boojho carries water in a transparent plastic bottle to his school. One day he left his bottle in the school. The bottle still had some water left in it. The following day, he observed some water droplets on the inner surface of the empty portion of the bottle. These droplets of water were formed due to 

(a) boiling and condensation.          (b) evaporation and saturation.

 (c) evaporation and condensation. (d) condensation and saturation. 

10. Paheli asked for a glass of water from Boojho. He gave her a glass of ice cold water. Paheli observed some water droplets on the outer surface of the glass and asked Boojho how these droplets of water were formed? Which of the following should be Boojho’s answer? 

(a) Evaporation of water from the glass.

 (b) Water that seeped out from the glass. 

 (c) Evaporation of atmospheric water vapour.

 (d) Condensation of atmospheric water vapour. 

VERY SHORT ANSWER QUESTIONS 

11. Sheela, Saima and Ravi have to dissolve maximum amount of sugar in the same amount of milk so as to win in a game.

 Ravi took hot boiling milk while Saima took ice cold milk. 

Sheela managed to get milk at room temperature. 

Whom do you think would win the game and why?

 12. Fill in the blanks with appropriate words:

 (i) Small pieces of stone can be removed from rice by __________.

 (ii) ___________ are obtained from stalks by threshing. 

(iii) Husk from wheat flour is generally removed by __________. (iv) The process of settling of heavier particles is called __________.

 (iv) Filtration is helpful in separating an insoluble __________ from a __________. 

13. State whether the following statements are true or false.

 (a) A mixture of oil and water can be separated by filtration.

 (b) Water can be separated from salt by evaporation.

 (c) A mixture of wheat grains and wheat flour can be separated by sieving. 

(d) A mixture of iron filings and rice flour can be separated by magnet.

 (e) A mixture of wheat grains and rice flakes can be separated by winnowing. 

 (f) A mixture of tea leaves and milk can be separated by decantation. 

SHORT ANSWER QUESTIONS 

14. Name and describe briefly a method which can be helpful in separating a mixture of husk from grains. What is the principle of this method?

 LONG ANSWER QUESTIONS 

15. Both Sarika and Mohan were asked to make salt solution. Sarika was given a teaspoonful of salt and half a glass of water, whereas Mohan was given twenty teaspoons full of salt and half a glass of water.

 (a) How would they make salt solutions?

 (b) Who would be able to prepare saturated solution?

 16. Paheli was feeling thirsty but there was only a pot of water at home which was muddy and unfit for drinking. How do you  think Paheli would have made this water fit for drinking if the following materials were available to her. Alum, tub, muslin cloth, gas stove, thread, pan and lid. 

17. Read the story titled “WISE FARMER” and tick the correct option to complete the story. 

A farmer was sad/happy to see his healthy wheat crop ready for harvest. 

He harvested the crops and left it under the sun/rain to dry the stalks. To separate the seeds from the bundles of the stalk he handpicked/threshed them. 

After gathering the seed grains he wanted to separate the stones and husk from it. 

His wife winnowed/threshed them to separate the husk and later sieved/hand picked to remove stones from it.

 She ground the wheat grains and sieved/ filtered the flour. 

The wise farmer and his wife got a good price for the flour. 

Can you tell why? 

18. You are provided with a mixture of salt, sand, oil and water. Write the steps involved for the separation of salt, sand and oil from the mixture by giving an activity along with the diagram. 

19. A mixture of iron nails, salt, oil and water is provided to you. Give stepwise methods to separate each component from this mixture? 

class 7 assignment nutrition in animals

NUTRITION IN ANIMALS

CLASS 7

ASSIGNMENT

Multiple Choice Questions (MCQs)

Question 1:Given below from (i) to (iv) are some food items.
(i) Boiled and mashed potato
(ii) Glucose solution
(iii) A slice of bread
(iv) Mustard oil
Which of the above will give blue-black colour when tested with iodine?
(a) (i) and (ii)
(b) (i) and (iii)
(ii) and (iii)
(d) (iii) and (iv)

Question 2:Which of the following pair of teeth differ in structure but are similar in function?
(a) Canines and incisors
(b) Molars and premolars
(c) Incisors and molars
(d) Premolars and canines

Question 3:Read carefully the terms given below. Which of the following set is the correct combination of organs that do not carry out any digestive functions?
(a) Oesophagus, large Intestine, rectum
(b) Buccal cavity, oesophagus, rectum
(c) Buccal cavity, oesophagus, large intestine
(d) Small intestine, large intestine, rectum

Question 4:The swallowed food moves downwards in the alimentary canal because of
(a) force provided by the muscular tongue
(b) the flow of water taken with the food
(c) gravitational pull
(d) the contraction of muscles in the wall of foodpipe

Question 5:The acid present in the stomach
(a) kills the harmful bacteria that may enter along with the food
(b) protects the stomach lining from harmful substances
(c) digests starch into simpler sugars
(d) makes the medium alkaline

Question 6:The finger-like outgrowths of Amoeba helps to ingest food. However, the finger-like outgrowths of human intestine helps to
(a) digest the fatty food substances
(b) make the food soluble
(c) absorb the digested food
(d) absorb the undigested food

Question 7:Read the following statements with reference to the villi of small intestine.
(a) They have very thin walls.
(b) They have a network of thin and small blood vessels close to the surface.
(c) They have small pores through which food can easily pass.
(d) They are finger-like projections.
Identify those statements which enable the villi to absorb digested food.
Choose the correct option.
(a) (i), (ii) and (iv)
(b) (ii), (iii) and (iv)
(c) (iii) and (iv)
(d) (i) and (iv)

Question 8:The false feet of Amoeba are used for
(a) movement only
(b) capture of food only
(c) capture of food and movement
(d) exchange of gases only

Question 9:The enzymes present in the saliva convert
(a) fats into fatty acids and glycerol
(b) starch into simple sugars
(c) proteins into amino acids
(d) complex sugars into simple sugars

Question 10:Cud is the name given to the food of ruminants which is
(a) swallowed and undigested
(b) swallowed and partially digested
(c) properly chewed and partially digested ,
(d) properly chewed and completely digested

Very Short Answer Type Questions

Question 11:Name the parts of the alimentary canal where
(a) water gets absorbed from undigested food
(b) digested food gets absorbed
(c) taste of the food is perceived
(d) bile juice is produced

Question 12:Choose the odd one out from each group and give reasons.
(a) Liver, salivary gland, starch, gall bladder
(b) Stomach, liver, pancreas, salivary gland
(c) Tongue, absorption, taste, swallow
(d) Oesophagus, small intestine, large intestine, rectum

Question 13:Fill in the blanks with suitable words:
(a) The alimentary canal stretches from………. to………….
(b) Teeth are rooted in separate……. in between the………………………
(c) Digestion of food starts in………… and gets completed in……………
(d) ………. is the largest gland in the human body.

Question 14:Following statements describe the five steps in animal nutrition. Read each statement and give one word for each statement. Write the terms that describe each process.
(a) Transportation of absorbed food to different parts of body and their utilisation.
(b) Breaking of complex food substances into simpler and soluble substances.
(c) Removal of undigested and unabsorbed solid residues of food from the body.
(d) Taking food into the body.
(e) Transport of digested and soluble food from the intestine to blood vessels.

Question 15:Fill in the blanks using the words listed below.
Water, front, intestinal, salts, pseudopodia, back, vacuole
(a) The digestion of all food components is completed by the……………….
(b) Large intestine absorbs…….. and some……… from the undigested food.
(c) Tongue is attached at the………… floor of the mouth cavity and is free at the
(d) Amoeba pushes out around the food and traps it in a food

class 8 assignment combustion flame and fuel

COMBUSTION,FLAME AND FUEL.

CLASS 8

ASSIGNMENT

1. A substance which reacts with oxygen giving heat is called a combustible substance. Which, one of the following is a combustible substance?
 (a) iron nail (c) stone piece (b) glass (d) wood 
2. Which one of the following has the highest calorific value?
 (a) kerosene (c) LPG (b) biogas (d) petrol 
3. Magnesium ribbon on burning in air produces
 (a) magnesium oxide, water and light
 (b) magnesium oxide and heat
 (c) magnesium oxide, heat and light 
(d) magnesium oxide, water and heat 
4. Which of the following is not a combustible substance?
 (a) camphor (c) straw (b) glass (d) alcohol 
5. The substance that does not burn with flame is
 (a) LPG (c) dry grass (b) camphor (d) charcoal
 6. On placing an inverted tumbler over a burning candle, the flame extinguishes after some time. This is because of nonavailability of (a) oxygen (c) carbon dioxide (b) water vapours (d) wax
 7. If a person’s clothes catches fire, the best way to extinguish the fire is to: 
(a) throw water on the clothes. (b) use fire extinguisher. 
(c) cover the person with a woolen blanket. 
(d) cover the person with a polythene sheet. 
 8. The substance expected to have the highest ignition temperature out of the following is
 (a) kerosene (c) coal (b) petrol (d) alcohol 
9. Choose the correct statement about inflammable substances from the following. They have: 
(a) low ignition temperature and cannot catch fire easily.
 (b) high ignition temperature and can catch fire easily. 
(c) low ignition temperature and can catch fire easily. 
(d) high ignition temperature and cannot catch fire easily. 
10. Choose the incorrect statement from the following. Forest fires are usually due to:
 (a) carelessness of humans (b) cutting of trees 
(c) heat of sun (d) lightning strike
 11. The calorific value of a fuel is expressed in a unit called 
(a) kilojoule per litre 
(b) kilojoule per gram 
(c) kilogram per mililitre
 (d) kilojoule per kilogram 
12. In villages, people use wood as fuel because: 
(a) it is considered to be an ideal fuel.
 (b) of its easy availability and low cost.
 (c) it is environment friendly.
 (d) it catches fire easily. 
13. Which among the following is considered as the cleanest fuel? (a) cow dung cake (c) kerosene (b) petrol (d) hydrogen gas 
14. Choose the incorrect statement from the following. A good fuel is one which:
 (a) is readily available.
 (b) produces a large amount of heat.
 (c) leaves behind many undesirable substances. 
(d) burns easily in air at a moderate rate. 
15. Shyam was cooking potato curry on a chulha. To his surprise he observed that the copper vessel was getting blackened from outside. It may be due to: 
(a) proper combustion of fuel.
 (b) improper cooking of potato curry.
 (c) improper combustion of the fuel.
 (d) burning of copper vessel. 
 VERY SHORT ANSWER QUESTIONS 
16. Fill in the blanks in the following sentences.
 (a) A ____________ process in which a substance reacts with __________ to give off heat is called combustion. 
(b) When the clothes of a person catch __________, the person is covered with a __________ to extinguish fire. 
(c) The __________ temperature at which a substance catches fire is called its __________ temperature. 
(d) The substances which have very ________________ ignition temperature and can easily catch fire with a flame are called __________ substances.
 (e) The substances which vapourise during __________, give flame. 
17. Some words (underlined) in the following sentences are jumbled up. Write them in their correct form. 
(a) Seldie is a combustible substance.
 (b) Slags is a non-combustible material. 
(c) Chittsmack does not burn by itself. 
(d) Some substances on combustion produce thea and mafel.
 (e) The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its ficalroic value.
 18. Two glass jars A and B are filled with carbon dioxide and oxygen gases, respectively. In each jar a lighted candle is placed simultaneously. In which jar will the candle remain lighted for a longer time and why?
 19. Anu wants to boil water quickly in a test tube. On observing the different zones of the flame, she is not able to decide which zone of the flame will be best for boiling water quickly. Help her in this activity. 
20. Why is the use of diesel and petrol as fuels in automobiles being replaced by Compressed Natural Gas (CNG) in big cities?

REVISION QUESTION FOR CLASS 8

SOME NATURAL PHENOMENA

CLASS-8

1. Which of the following cannot be charged easily by friction?
(a) A plasticscscale	(b) A copper rod	(c) An inflated balloon	(d) A woollen cloth.

(a) negative charge (b) positive charge (c ) both positive and negative charge				(d) becomes neutral
4. An electroscope is a device used to:
(a) detect and test small electric charges			(c ) test the presence of magnetic filed
(b) calculate the amount of electrical charge flowing through the conductor (d) none of these
5. Lighting conductors are made of:
(a) plastic	(b) copper	(c ) wood	(d) bakelite

(1)…………….. is a form of static electricity.

(2)When lightning heats the air and causes it to expand rapidly,……………. Is produced.

(3)A charged body attracts an ……………… body.

(4)…………… between two bodies is definite proof that of them are charged

Question and answer.1.What are the two types of charges ?2.Name the material used to transfer of charges from one body to other.3.Name the device which is used to test whether an object is charged or not.4.Define lightning conductor.1.Sometime, a crackling sound is heard while taking off sweater during winters. Explain.2.Explain why a charged body loses its charge if we touch it with our hand.3.Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?4.The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.5.Why does a charged body attract an uncharged body?1.How many different types of charges are there ? Write the nature of charges on glass rod and silk cloth when they are rubbed each other ?2.What are the causes of sparkling ?3.What is electric discharge ? How does it occur ?4.How does electric discharge occur in clouds ?5.What is static electricity ? How is it differ from electric current ?1.Suggest some measures to protect ourselves from lightning.2.Describe with the help of a diagram an instrument which can be used to detect a charged body.3.Draw and explain the function of Electroscope?4.Write Do’s and Dont’s during thunderstorm.2.When a glass rod is rubbed with a piece of silk cloth the rod(a) and the cloth both acquire positive charge.(b) becomes positively charged while the cloth has a negative charge.(c) and the cloth both acquire negative charge.(d) becomes negatively charged while the cloth has a positive charge.3.When a glass rod is rubbed with a silk cloth, it acquires a6. When a woollen cloth removed in the dark. We see sparks and hear a cracking sound. This is due to:

REVISION QUESTION FOR CLASS 6 THE LIVING AND NON-LIVING THINGS.

THE LIVING AND NON-LIVING THINGS

CLASS 6

Q.I. Define the following.

a. Lifespan

b. Excretion

c. Stimulus

d. Organ System

e. Respiration

f. Tissue

g. Organ

h. Cell

II. Fill in the blanks.

 Green plants are called____________________ .

Green leaves contain pigment to absorb solar energy____________________.

III. Choose the correct option.

1. Fish absorbs oxygen from water through their

a. Lungs                   b. Gills                  c. Skin               d. Gall bladder

2. Which one animal move away from light?

a. Earthworms         c. Snail

b. Snake                 d. Monkey

I. Answer the following questions:

1. What are living things?

2. What are non-living things?

3. What are natural things?

4. What are man-made things?

5. Give two examples of living things.

6. Give two examples of non-living things.

7. What are the properties of matter.

8. Give two examples of man-made things.

9. What are the five differences between living things and non-living things?

10. Write six features of living things.

II. Fill in the blanks with the correct words:

1. All plants and _________ are living things. (animals/wood)

2. Most plants grow from _________. (seeds/eggs)

3. Non-living things found in nature are called _________ things. (man-made/natural)

4. Non-living things made by man are called _________ things. (man-made/natural)

5. Animals lay _________ or give birth to young ones. (seeds/eggs)

REVISION QUESTION FOR CLASS 7

MATTER AND CHEMICAL FORMULAE

Q.1 Write the symbols of the following elements

1) Zinc                                     6) Phosphorus

2) Manganese                           7) Nickel

3) Potassium                             8) Calcium

4) Calcium                                9) Lead

5) Gold                                    10) Neon

Q.2 Find the valencies of the element

1) BaCl2

2) FeO

3) Fe2O3

4) CaCO3

5) Na2O

6) Al(OH)3

7) SO2

8) NH3

Q.3 Define the following terms.

1) Valency                             4) Molecule

2) Formula                            

3) Symbol 

Q.4 Write the formula of the following compounds

1) Nitric acid                      5) Potassium carbonate

2) Ammonia                       6) Calcium oxide

3) Sodium hydroxide          7) Carbon monoxide

4) Hydrogen chloride          8) Sulphuric acid

Q.5 Give examples each of the following.

1) Biatomic molecules

2) Monoatomic  molecules               4) Triatomic molecules

3 ) Noble gas

Q.6 Write the valency/valencies of the following

1) Hydrogen                                5) Iron

2) Carbon                                    6) Copper

3) Nitrogen                                  7) Sulphur

4) Phosphorus                              8) Lead

Q.8 Match the following.

        A                                     B

1) Potassium                  a) Aurum

2) Iron                           b) Stannum

3) Silver                        c) Ferrum

4) Gold                         d) Argentum

5) Tin                            e) Kalium

REVISION QUESTIONS FOR CLASS 8

FORCE

   

• Fill in the blanks:

(1 marks each)

(1) To draw water from a well we have to ———  the rope.

(2)A charged body ———— an uncharged body towards it.

(3)To move a loaded trolley we have to ———— it.

(4)The north pole of a magnet ———— the north pole of another magnet.

(5)To stretch the bow, the archer applies a force that causes a change

in its ——.

(6)The force applied by the archer to stretch the bow is an example of ——— force.

(7)The type of force responsible for a change in the state of motion of the arrow is an example of a --------------------.

(8)While the arrow moves towards its target, the forces acting on it are due to ————

(9)At the same depth, a liquid exerts ———— pressure in all directions.

(10)Unlike poles of a magnet ———— each other.

VERY SHORT ANSWER QUESTIONS :

(1 marks )

1.A ball is in rest. Push it gently. Does the ball begin to move?

2.Name the term used to express the strength of a force.

3.What is force ?

4.When does net force becomes zero?

5.Give two examples of muscular force.

6.Give an example of non-contact force.

7.Give two examples of contact force.

8.What do you mean by electrostatic force?

SHORT ANSWER QUESTION

(2 marks )

1.A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

2 .An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

3.A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.

ANSWER THESE QUESTIONS

(3 Marks)

     1.Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.

2.What are contact force. State different contact force.

3.What are non-contact force. State different non-contact force.

4.What are the various effects of force on different objects.

5.Explain force of gravity.

LONG ANSWER QUESTION

(5 marks each)

1.What is electrostatic force? Proof with the help of diagram.

2.What is friction? Explain with example types of non contact forces.

3.Prove that the force of friction depends on two surfaces in contact.

•MULTIPLE CHOICE QUESTION:

1.An example of contact force is:

(i)Gravitational force

(ii)Frictional force

(iii)Magnetic force

(iv)Electro-static force

2.An example of a non-contact force is:

(i)Magnetic force

(ii)Muscular force

(iii)Frictional force

(iv)all of these

3.If force is applied to an object in the direction of its motion. Its speed will:

(i)decreased

(ii)increases

(iii)remain unchanged

(iv)none of these

4.The SI unit if force is

(i)Newton

(ii)Newton/metre2

(iii)Pascal

(iv)none if these

5.Force of friction brings about a:

(i)change in speed of the object

(ii)change in shape of the object

(iii)change in direction of the object

(iv)none of these

6.Which force do you use when you ride a bicycle?

(i)Muscular force

(ii)Frictional force

(iii)Electrostatic force

(iv)Magnetic force