15. Describe an experiment to demonstrate that water
absorbs heat during boiling at a constant
temperature.
16. State (a) the melting point of ice and (b) the
boiling point of water.
17. What is evaporation ?
18. State three factors which affect the rate of
evaporation of a liquid.
19. Wet clothes dry more quickly on a warm dry day
than on a cold humid day. Explain.
Answers
Solution:
Aim: Water absorbs heat during boiling at a constant temperature
Equipments required: Water, Beaker, Burner, Tripod stand, Vertical stand wire gauze
Explanation: Take some water in the beaker. Suspend a thermometer in a beaker in water so that the bulb of the thermometer remains in water without touching the bottom or the sides. Supply the heat by the burner and note the temperature at room temperature.
Maintain the record of temperature after every minute.
Temperature rises and as it reaches 100°C water starts boiling. Though heat is being supplied, the temperature does not rise and it remains constant at 100°C and bubbles formed are seen.
Conclusion: boiling point of water is 100°C and at boiling point heat supplied is absorbed by water at constant temperature.
16.The melting point of ice is 0°C. (b) The temperature at which water starts changing from water to vapours. The boiling point of water is 100°C..
17. Theprocess of turning from liquid into vapour.
18.Factors That Affect the Rate of Evaporation
temperature of the liquid. A cup of hot water will evaporate more quickly than a cup of cold water.
exposed surface area of the liquid. ...
presence or absence of other substances in the liquid. ...
air movement. ...
concentration of the evaporating substance in the air.
19.Clothes dry more quickly on a warm day than on a cold humid day because the rate of evaporation is directly proportional to temperature. Higher the rate of evaporation on the hot day compared to the cold days..
Explanation:
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Answer:
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