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FRICTION CLASS-VII

 worksheet-I

 1 Explain Why, it is easier to drag a mat on floor when nobody is sitting on it but much more difficult to drag the same mat when a person is sitting on it.
2 Which type of surfaces produce {a} least friction, and {b} too much friction? What is the direction of force of friction acting on a moving object?
3  Why do kabaddi players rub their hands with dry soil?
4 Why are cars, airplanes & rockets streamlined?
5  What is the special name of frictional force exerted by fluids (like air or water)? 
 6. What are the factors that affect the fluid friction?7
7  What is the name of ‘special shape’ which is given to objects moving through fluids to reduce drag? 
8 Fill in the blanks:
(a) Sprinkling of powder on the carom board ………………. Friction.
 
(b) Ball bearings reduce friction because they …………………rather than slide. 
9 Two men tried to push a heavy box & could  not succeed. Finally wheels were fitted to the box & now a single man could move it. Justify. 
10.  What prevents you from slipping every time you take a step forward?
11 What happens when you rub your hands vigorously for a few seconds? Why does this happen?
12. Explain why:
(a) a pencil will write on paper but not on glass
(b) The handles of motor cycle are covered with a rubber sheet with spikes.(c) The soles of our shoes wear out gradually.
(d) Tyres of car wear out gradually.

CLASS-IX                                        CHEMISTRY
Note- Please write the answer in tabular form where ever required.
          Use the scientific terms and stress on key words while writing answers .



1. Classify the following substances as elements,compounds or mixtures.
   Sodium, Brass, Ammonia, Iron, Common salt, Stainless steel. Blood, Soda water, Oxygen , Milk, Glass'      Iron filings.

2.Name the type of colloids in each in which dispersed phase and dispersed medium are respectively
(a) silid and gas
(b) Liquid and solid

3.Define solution. If 10ml of SULPHURIC ACID IS DISSOLVED IN 90ML OF WATER. CALCULATE THE CONCENTRATION OF SULPHURIC ACID IN THE SOLUTION.

4. (a)WHICH OF THE FOLLOWING WILL SHOW TYNDALL EFFECT?Why ?
Salt solution, Milk, Copper Sulphate Solution.

   (b) Which of the two will scatter light. Soap solution or salt solution

5.What is evaporation ? In the following factors state which factor is responsible for the change in the rate of evaporation.

(a) Clothes dre faster on a windy day.

(b) Wet clothes dry faser on spreadind them

(c) Clothes dry faster in sun than in shade.

6.What is the effect of temperature on solubility of a solid in liquid?

7,110g of salt is present in 550g of solution. Calculate the concentration of the solution.?

8. A 5% sugar solution means that

  (a) 15ml alcohol and 85ml water.

  (b) 15ml alcohol and 100ml water

9. What is sublimation? Name two substances that undergo sublimation.

10. Which phenomenon occurs during the following changes?
   (a) Formation of clouds
   (b) Wax melts in the sun.
   (c) Size of naphthalene ball decrease
   (d) Wax melts in the sun

11.Express the following temperature in Kelvin scale
  (a) 25 degree C  (b) 373 degree C

12.Give two examples from daily life where tyndall effect is observed.

13.An alloy cannot be separated into its constituents by physical methods but still it is considered as ashomogeneous mixture. Explain.

13,Classify the following as homogeneous and heterogeneous mixtures

 Alloy, Milk, Air, Sugar solution in water. Smoke, Natural gas , Soap bubbles, Alcohol in water Iron filings and sulphur.

14.. You are given a pure substance . How would you test  the purity of the given substance?

15.MULTIPLE CHOICE QUESTIONS

1. Which of the following is/are example of suspension?

(A) Muddy water (B) Slaked lime (C) Paints (D) All

2. Which of the following statement is not true about suspension ?

(A) The particles of suspension can be separated from solvent by the process of filtration.

(B) When the suspension is kept undisturbed the particles of suspension settle down.

(C) A suspension is homogeneous in nature.

(D) Scattering of light take place in suspension.

3. Fog is an example of -

(A) foam (B) emulsion (C) aerosol (D) gel

4. Which of the following statement is not true about colloidal solution ?

(A) These are visible under powerful microscope.

(B) Their particles do not settle down with passage of time

(C) Their particles are electrically charged.

(D) These are homogeneous in nature.

5. Which of the following is an example of emulsion ?

(A) Face cream (B) Shaving cream (C) Honey (D) Smoke

6. Soap solution is an example of -

(A) true solution (B) suspension (C) colloidal solution (D) none of these

7. When a beam of light is passed through a colloidal solution, it gets -

(A) reflected (B) absorbed (C) scattered (D) refracted

8. Which of the following is an example of gel ?

(A) Coloured gem (B) Jelly (C) Smoke (D) Shaving cream

9. Which of the following will show Tyndall effect ?

(A) Starch solution (B) Sodium chloride solution

(C) Copper sulphate solution (D) Sugar solution

10. Colloidal particles can be normally seen by

(A) naked eye (B) optical microscope

(C) electron microscope (D) telescope

MATTER IN OUR SURROUNDINGS

  1. As solid melts to form liquid:

 a. Inter particle distance increases

 b. Inter molecular forces of attraction decreases

c. Compressibility increases

d. All of the above

2. Which of the following is not characteristic of solid:

a. High Rigidity b. Regular Shape c. High density d. High compressibility

3. The boiling point of water is:

a. 101 oC at atmospheric pressure

b. 273K at atmospheric pressure

 c. 0 oC at atmospheric pressure

d. 0K at atmospheric pressure

4. Which of the following has highest intermolecular forces of attraction?

a. Water at room temperature

 b. CO2 gas

c. Ethyl alcohol

d. Iron metal

5. Which of the following substances will undergo sublimation?

 a. Common salt b. Odonil c. Sugar d. Sand

6. The process of evaporation causes:

a. Cooling b. Heating c. Dryness d. None of the above

7. The conversion of solid to gas directly is called:

 a. Evaporation b. Sublimation c. Distillation d. condensation

8. Evaporation of a liquid can take place:

a. At its boiling point b. At all temperatures c. At its freezing point d. At a fixed temperature

11. At higher altitudes the boiling points of liquids

a. Increases b. Decreases 3 Chemistry  c. Remains the same d. Increases then decreases

12. During evaporation particles of a liquid change into vapours :

a. From the surface b. From the bulk c. From the bottom d. From all over the liquid

13. In which phenomenon does water change into water vapour below its boiling point:

a. Boiling b. Evaporation c. Freezing d. Sublimation

14. We get the smell of hot food in the kitchen outside the house because of:

a. Boiling b. Evaporation c. Sublimation d. Diffusion

15. which are the favourable conditions for liquefaction of petroleum gas:

 a. High pressure, high temperature

b. Low pressure, low temperature

 c. High pressure, low temperature

 d. Low pressure, high temperature

16. latent heat of vapourisation is used to:

 a. Overcome forces of attraction between the liquid particles at the boiling point

b. Overcome forces of attraction between solid particles at the freezing point

c. Increase the kinetic energy of particles in the liquid state

d. Increase the kinetic energy of the particles in the vapour phase

17. Which of the following has highest density?

 a. Kerosene b. Water c. Iron d. Wood

18. Dry ice on heating produces:

a. Liquid CO2 b. Gas CO2 c. Liquid water d. Water vapour

19. Particles move randomly in:

 a. Water b. Sugar c. Nitrogen d. Dry ice

20. When we blow air into the balloon it inflates because:

 a. Air particles diffuse into the balloon

 b. Air particles collide with the walls of the balloon and exert pressure on them

c. Rubber is elastic in nature

d. The temperature of air in the balloon increases

Is MATTER AROUND US PURE?

1. When a bottle of soda water is opened, carbon dioxide escapes, producing a fizz. This is due to: a. Decrease in solubility on decreasing temperature

 b. Decrease in solubility on increasing temperature

 c. Decrease in solubility on decreasing pressure

d. Decrease in solubility on increasing pressure

2. A mixture of oil and water can be separated by:

a. Sublimation b. Crystallisation c. Chromatography d. Separating funnel

Questions 3 to 5 are based on the following information:

Four samples A, B, C, D are prepared by adding a pinch of copper sulphate, a spatula of copper sulphate, a spatula of chalk powder, and some milk, to water respectively.

 3. Which one is the colloidal solution among them?

 a. C b. D c. B d. A

 4. Which of these will form a clear and transparent solution:

 a. A b. B c. A and B d. B and D

5. Which of these will exhibit the Tyndall effect?

a. A and D b. B and C c. A and B d. D

                            ALL THE BEST

chemistry practical for claa9