Saturday, 2 September 2017

CLASS 9 REVISION PAPER FOR PERIODIC TEST -2

PRACTICE PAPER


1. What is Tyndall effect? Why the solution of copper sulphate does not show Tyndall effect? 

2. A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C? Comment.

3. Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.

4. 5ml of dettol is added to a beaker containing 500 ml of water and stirred.State any two observations that you make.

 5. Classify the following into osmosis/diffusion
(a)      Swelling up of a raisin on keeping in water.
(b)      Spreading of virus on sneezing.
(c)     Earthworm dying on coming in contact with common salt.
(d)      Shrinking of grapes kept in thick sugar syrup.
(e)     Preserving pickles in salt.

6. Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.

7. Answer the following:

a)     Under which category of mixtures will you classify alloys and why?
b)     A solution is always a liquid. Comment.
c)      Can a solution be heterogeneous?

8. Iron filings and sulphur were mixed together and divided into two parts, ‘A’ and ‘B’. Part ‘A’ was heated strongly while Part ‘B’ was not heated. Dilute hydrochloric acid was added to both the Parts and evolution of gas was seen in both the cases. How will you identify the gases evolved?

9. A child wanted to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in Fig. 2.3. The filter paper was removed when the water moved near the top of the filter paper.

a). What would you expect to see, if the ink contains three different coloured components?

b). Name the technique used by the child.
c). Suggest one more application of this technique.











10. Classify each of the following, as a physical or a chemical change. Give reasons.
(a)    Drying of a shirt in the sun.

(b)    Rising of hot air over a radiator.
(c)    Burning of kerosene in a lantern.
(d)    Change in the colour of black tea on adding lemon juice to it.
(e)    Churning of milk cream to get butter.

11. During an experiment the students were asked to prepare a 10% (Mass/Mass) solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water while Sarika prepared it by dissolving 10g of sugar in water to make 100g of the solution.
(a)    Are the two solutions of the same concentration
(b)    Compare the mass % of the two solutions.

12.  You are provided with a mixture containing sand, iron filings, ammonium chloride and sodium chloride. Describe the procedures you would use to separate these constituents from the mixture?

13. While diluting a solution of salt in water, a student by mistake added acetone
(boiling point 56°C). What technique can be employed to get back the acetone? Justify your choice.

14. What would you observe when

(a)    a saturated solution of potassium chloride prepared at 60°C is allowed to cool to room temperature.

(b)    an aqueous sugar solution is heated to dryness.
(c)    a mixture of iron filings and sulphur powder is heated strongly.

15. Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do.

16. (b) You are given two substances ‘X’ AND ‘Y’ .One of these is pure water and another is impure. How will you identify which one is pure water?

17. Smoke and fog both are aerosols. In what way are they different?

18. You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils at 100°C and sample ‘B’ boils at 102°C. Which sample of water will not freeze at 0°C?

Comment.

19. An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?

20. Give an example each for the mixture having the following characteristics. Suggest

a suitable method to separate the components of these mixtures

(a)             A volatile and a non-volatile component.

(b)             Two volatile components with appreciable difference in boiling points.

(c)    Two immiscible liquids.

21. Which of the following are not compounds?

(a)   Chlorine gas
(b)   Potassium chloride
(c)   Iron
(d)   Iron sulphide
(e)   Aluminium

(f)   Iodine
(g)   Carbon
(h)   Carbon monoxide
(i)   Sulphur powder

22. Give some examples of Tyndall effect observed in your surroundings?

23. Osmosis is a special kind of diffusion’. Comment.

24. (a) List two important precautions a student should take while determining the melting point of ice?          
   (b) A student prepared three solutions-(i) Copper sulphate in water (ii) soil in water (iii) milk in water. Distinguish between the three based on their particle size and stability.

25. In which of the following substances you expect strongest and the weakest force of attraction  between the particles .Give reason for your answer
          Water, Sodium chloride, Carbondioxide
   













Sunday, 14 May 2017

CLASS 11 HOLIDAY HOMEWORK 2017-18

MOLE CONCEPT

1. What is the value of one mole?

2. Calculate the number of molecules present in 0.5 moles of CO2?

3. If atomic mass of Mg atom is 24 g, find mass of 1 Mg atom.

4. Two containers A & B are filled with 4 gram hydrogen gas and 32 gram oxygen gas respectively. Which of the two containers have more moles?

5. How much copper can be obtained from 100g copper sulphate?

6. A 12g sample of a gas occupies 19.2 litres at STP. What is the molecular weight of the gas? 

7. A balloon is filled with helium gas at STP, the volume of the balloon is 2.24dm3. Find the amount of helium gas in terms of moles?

8. Calculate the number of atoms in each of the following. (a) 52 moles Ar (b) 52 u He (c) 52g He.

9. What is molar volume?

10. Calculate the number of bromide ions in 3 moles of mercury(II)bromide?

11. One gram molecule of H2O contains how many moles of molecules and number of molecules?

12. How many moles are present in 15g of C2H4(ethylene)?

13. In 14g of N2 calculate no.of atoms?

14. Define mole?

15. Why was there need to use this number called mole?