Question

DELHI PUBLIC SCHOOL BOPAL, AHMEDABAD
CLASS 9 CHEMISTRY ASSIGNMENT
SESSION 2019 - 20

Chapter 1 Matter in our Surroundings

1. 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.
2. You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster?
3. Comment on the following statements.
(a) Evaporation causes cooling. (b) Rate of evaporation of an aqueous solution decreases with increase in humidity. (c) Sponge though compressible is a solid.
4. At which temperature the solid and liquid states of a substance can exist together?
5. What is the effect of pressure on boiling point?
6. How is the rate of diffusion different in liquids and solids? Give reason.
7. A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following would correctly represent the result? Justify your choice.

8. A balloon when kept in sun, bursts after some time. Why?
9. Distinguish between evaporation and boiling.
10. How is the high compressibility property of gas useful to us?
11. A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator (temperature <0° C). If you could measure the temperature of the content of the tumbler, which of the following graphs would correctly represent the change in its temperature as a function of time.

12. Look at the figure and suggest in which of the vessels A, B, C or D, the rate of evaporation will be the highest? Explain.

13. Write the chemical name of dry ice. Justify its name. How it is stored?
14. What happen to the rate of diffusion if the temperature is increased?
15. What will happen if the pressure is reduced on solid carbon dioxide (dry ice)?
16. Name any three substances that show sublimation.
17. Why do we see water droplets collected on the outer surface of a glass container, containing ice?​

Answer 1

Answer:

The water is impure.

Impurities in water increases its boiling point and decreases its freezing point.This is why the boiling point has become 102⁰c...suggesting that its freezing point will be also less than 0°C.