Class notes Chemistry Assessment2120

Question1. The rate of evaporation depends upon - (a) surface area (b)temperature (c) humidity (d) all of these Answer. Correct answer is (d) All of these - We known that evaporation is the surface phenomena, particle gain enough energy to overcome the force of attraction present in liquid and change into vapour state. - Evaporation is directly proportional to temperature, higher the temperature more will be the rate of evaporation. - Humidity is the amount of water vapour present in air. If the amount of water vapour is already high the rate of evaporation decreases. Question 2. On summer days, I was serving a glass of cold fruit Juice to our guest and I observed water droplet on to the outer wall of the glass, why it happened? Answer. The water vapour present in the air comes in the contact with cold water, looses its energy and condenses to liquid state, which we can see in the form of water droplets on the outer wall of the glass. Question3. Why sanitizer or acetone gives you cooling sensation? Class 9 Science | Matter In Our Surroundings | DPP Solutions