Short Answer Questions 11. 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. 12. 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 (Fig. 1.1) would correctly represent the result? Justify your choice. Fig. 1.1 13. Fill in the blanks: (a) Evaporation of a liquid at room temperature leads to a——— effect. (b) At room temperature the forces of attraction between the particles of solid substances are———than those which exist in the gaseous state. (c) The arrangement of particles is less ordered in the ——— state. However, there is no order in the ——— state. (d) ——— is the change of gaseous state directly to solid state without going through the ———state. (e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called———. 14. Match the physical quantities given in column A to their S I units given in 15. The non S I and S I units of some physical quantities are given in column A and column B respectively. Match the units belonging to the same physical quantity:column B : (A) (B) (a) Pressure (i) cubic metre (b) Temperature (ii) kilogram (c) Density (iii) pascal (d) Mass (iv) kelvin (e) Volume (v) kilogram per cubic metre (A) (B) (a) degree celsius (i) kilogram (b) centimetre (ii) pascal (c) gram per centimetre cube (iii) metre (d) bar (iv) kelvin (e) milligram (v) kilogram per metre cube MATTER IN OUR SURROUNDINGS 9 16. ‘Osmosis is a special kind of diffusion’. Comment. 17. 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. (f) Spreading of smell of cake being baked through out the house. (g) Aquatic animals using oxygen dissolved in water during respiration. 18. Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations. 19. 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. 20. 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 (Fig.1.2) would correctly represent the change in its temperature as a function of time. Fig. 1.2 21. Look at Fig. 1.3 and suggest in which of the vessels A,B, C or D the rate of evaporation will be the highest? Explain. Moving Fan Fig. 1.3 22. (a) Conversion of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid. (b) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion? EXEMPLAR PROBLEMS

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