Matter in Our Surroundings -1 : āĻāĻŽāĻžā§° āĻāĻžā§°āĻŋāĻāĻāĻžāĻˇā§° āĻĒāĻĻāĻžā§°ā§āĻĨ : Question with Answer
1. Desert cooler āĻāĻāĻžāĻ āĻļā§āĻˇā§āĻ āĻā§°āĻŽ āĻĻāĻŋāĻ¨āĻ¤ āĻāĻžāĻ˛āĻā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻā§°ā§ āĻāĻŋā§ ?Why does a desert cooler cool better on a hot dry day ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻļā§āĻˇā§āĻ āĻā§°āĻŽ āĻĻāĻŋāĻ¨āĻ¤ āĻŦāĻžāĻ¯āĻŧā§āĻ¤ āĻāĻ°ā§āĻĻā§āĻ°āĻ¤āĻž āĻāĻŽ āĻĨāĻžāĻā§āĨ¤ āĻ¸ā§ā§ā§ āĻĒāĻžāĻ¨ā§ āĻĻā§āĻ°ā§āĻ¤ āĻŦāĻžāĻˇā§āĻĒā§āĻā§āĻ¤ āĻšā§ āĻā§°ā§ āĻ āĻ§āĻŋāĻ āĻ āĻžāĻŖā§āĻĄāĻž āĻā§°ā§āĨ¤ On a hot dry day, humidity in the air is low. So water evaporates faster and gives more cooling.
2. āĻā§āĻ°ā§āĻˇā§āĻŽāĻāĻžāĻ˛āĻ¤ āĻŽāĻžāĻāĻŋā§° āĻāĻ˛āĻšā§° āĻĒāĻžāĻ¨ā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻšā§ āĻĨāĻžāĻā§ āĻāĻŋā§ ? Why does water remain cool in an earthen pot during summer ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻāĻ˛āĻšā§° āĻ¸ā§°ā§ āĻ¸ā§°ā§ ā§°āĻ¨ā§āĻ§ā§ā§°ā§°ā§ āĻĒāĻžāĻ¨ā§ āĻŦāĻžāĻˇā§āĻĒā§āĻā§āĻ¤ āĻšā§ āĻā§°ā§ āĻ¤āĻžāĻĒ āĻļā§āĻˇāĻŖ āĻā§°ā§āĨ¤ āĻ¸ā§ā§ā§ āĻĒāĻžāĻ¨ā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻĨāĻžāĻā§āĨ¤ Water evaporates through tiny pores of the pot and absorbs heat, so the water remains cool.
3. āĻšāĻžāĻ¤ā§° āĻ¤āĻ˛ā§ā§ąāĻžāĻ¤ āĻāĻāĻŋāĻāĻ¨, āĻĒā§āĻā§āĻ°āĻ˛ āĻŦāĻž āĻ¸ā§āĻāĻ¨ā§āĻ§āĻŋ āĻāĻ¤ā§° āĻĸāĻžāĻ˛āĻŋ āĻ˛’āĻ˛ā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻ āĻ¨ā§āĻā§ą āĻšā§ āĻāĻŋā§ ? Why do we feel cool when acetone, petrol or perfume is poured on the palm ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻāĻāĻŦā§ā§° āĻĻā§āĻ°ā§āĻ¤ āĻŦāĻžāĻˇā§āĻĒā§āĻā§āĻ¤ āĻšā§ āĻšāĻžāĻ¤ā§° āĻĒā§°āĻž āĻ¤āĻžāĻĒ āĻļā§āĻˇāĻŖ āĻā§°ā§āĨ¤ āĻ¸ā§ā§ā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻ āĻ¨ā§āĻā§ą āĻšā§āĨ¤ These substances evaporate quickly and absorb heat from the palm, causing cooling.
4. āĻā§°āĻŽ āĻāĻžāĻš āĻŦāĻž āĻāĻžāĻā§ā§° āĻāĻžāĻĒāĻ¤āĻā§ āĻĒā§āĻ˛ā§āĻāĻ¤ āĻ˛ā§ āĻā§ā§ąāĻž āĻ¸āĻšāĻ āĻāĻŋā§ ? Why is it easier to drink hot tea or milk from a plate than from a cup ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻĒā§āĻ˛ā§āĻāĻ¤ āĻĒā§āĻˇā§āĻ āĻāĻžāĻ˛āĻŋ āĻŦā§āĻāĻŋ āĻšā§, āĻ¸ā§ā§ā§ āĻŦāĻžāĻˇā§āĻĒā§āĻāĻŦāĻ¨ āĻĻā§āĻ°ā§āĻ¤ āĻšā§ āĻā§°ā§ āĻāĻžāĻš āĻ¸ā§āĻ¨āĻāĻžāĻ˛ā§ āĻ āĻžāĻŖā§āĻĄāĻž āĻšā§āĨ¤ In a plate, the surface area is larger, so evaporation is faster and tea cools quickly.
5. āĻā§āĻ°ā§āĻˇā§āĻŽāĻāĻžāĻ˛āĻ¤ āĻāĻŽāĻŋ āĻāĻŋ āĻ§ā§°āĻŖā§° āĻāĻžāĻĒā§ā§° āĻĒāĻŋāĻ¨ā§āĻ§āĻŋāĻŦ āĻ˛āĻžāĻā§ ? What type of clothes should we wear in summer ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻā§āĻ°ā§āĻˇā§āĻŽāĻāĻžāĻ˛āĻ¤ āĻĒāĻžāĻ¤āĻ˛ āĻāĻĒāĻžāĻšā§ āĻāĻžāĻĒā§ā§° āĻĒāĻŋāĻ¨ā§āĻ§āĻŋāĻŦ āĻ˛āĻžāĻā§āĨ¤ We should wear light cotton clothes in summer.
6. āĻ¤āĻ˛ā§° āĻāĻˇā§āĻŖāĻ¤āĻžāĻŦāĻŋāĻ˛āĻžāĻ āĻā§āĻ¨ā§āĻāĻŋāĻā§āĻ°ā§āĻĄāĻ¤ āĻĒā§āĻ°āĻāĻžāĻļ āĻā§°āĻžāĨ¤ Convert the following temperatures into Celsius scale.
(a) 293 K
āĻāĻ¤ā§āĻ¤ā§° / Ans: 293 K = 20°C
(b) 470 K
āĻāĻ¤ā§āĻ¤ā§° / Ans: 470 K = 197°C
7. āĻ¤āĻ˛ā§° āĻāĻˇā§āĻŖāĻ¤āĻžāĻŦāĻŋāĻ˛āĻžāĻ āĻā§āĻ˛āĻāĻŋāĻ¨āĻ¤ āĻĒā§āĻ°āĻāĻžāĻļ āĻā§°āĻžāĨ¤ Convert the following temperatures into Kelvin scale.
(a) 25°C
āĻāĻ¤ā§āĻ¤ā§° / Ans: 25°C = 298 K
(b) 373°C
āĻāĻ¤ā§āĻ¤ā§° / Ans: 373°C = 646 K Science 9th : Ass / Eng
8(a). āĻā§āĻ˛āĻž āĻ āĻžāĻāĻ¤ āĻ¨ā§āĻĢāĻĨā§āĻ˛āĻŋāĻ¨ āĻŦāĻ˛ āĻā§āĻāĻĻāĻŋāĻ¨āĻŽāĻžāĻ¨ āĻĨā§ āĻĻāĻŋāĻ˛ā§ āĻ¨āĻžāĻāĻāĻŋā§āĻž āĻšā§ āĻāĻŋā§ ? Why do naphthalene balls disappear after some days in open air ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻ¨ā§āĻĢāĻĨā§āĻ˛āĻŋāĻ¨ āĻāĻ°ā§āĻ§ā§āĻŦāĻĒāĻžāĻ¤āĻ¨ āĻāĻā§ āĻ āĻ°ā§āĻĨāĻžā§ āĻāĻ āĻŋāĻ¨ā§° āĻĒā§°āĻž āĻĒā§āĻ¨ā§ āĻĒā§āĻ¨ā§ āĻā§āĻ āĻšā§ Naphthalene undergoes sublimation and changes directly from solid to gas.
8(b). āĻĻā§ā§°ā§° āĻĒā§°āĻžāĻ āĻāĻ¤ā§°ā§° āĻā§āĻ¨ā§āĻ§ āĻĒā§ā§ąāĻž āĻ¯āĻžā§ āĻāĻŋā§ ? Why can we smell perfume from a distance ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻāĻ¤ā§°ā§° āĻāĻŖāĻŋāĻāĻžāĻŦā§ā§° āĻŦāĻžāĻ¯āĻŧā§āĻ¤ āĻŦā§āĻ¯āĻžāĻĒāĻŋāĻ¤ āĻšā§āĨ¤ Perfume particles diffuse in air.
9. āĻāĻŖāĻŋāĻāĻžāĻŦā§ā§°ā§° āĻŽāĻžāĻā§° āĻāĻāĻ°ā§āĻˇāĻŖ āĻŦāĻ˛ā§° āĻā§°ā§āĻ§ā§āĻŦāĻā§āĻ°āĻŽāĻ¤ āĻ¸āĻā§ā§ąāĻž- āĻĒāĻžāĻ¨ā§, āĻā§āĻ¨āĻŋ āĻā§°ā§ āĻ āĻā§āĻ¸āĻŋāĻā§āĻ¨ Arrange water, sugar and oxygen in increasing order of force of attraction.
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻ āĻā§āĻ¸āĻŋāĻā§āĻ¨ < āĻĒāĻžāĻ¨ā§ < āĻā§āĻ¨āĻŋ (Oxygen < Water < Sugar)
10. āĻ¤āĻ˛ā§° āĻāĻˇā§āĻŖāĻ¤āĻžāĻ¤ āĻĒāĻžāĻ¨ā§ā§° āĻā§āĻ¤āĻŋāĻ āĻ ā§ąāĻ¸ā§āĻĨāĻž āĻāĻŋ ? What is the physical state of water at the following temperatures ?
(a) 25°C
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻā§āĻ˛ā§ā§āĻž / Liquid
(b) 0°C
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻāĻ āĻŋāĻ¨ āĻā§°ā§ āĻā§āĻ˛ā§ā§āĻž / Solid and Liquid
(c) 100°C
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻā§āĻ˛ā§ā§āĻž āĻā§°ā§ āĻā§āĻā§ā§ / Liquid and Gas
11(a). āĻ¸āĻžāĻ§āĻžā§°āĻŖ āĻāĻˇā§āĻŖāĻ¤āĻžāĻ¤ āĻĒāĻžāĻ¨ā§ āĻā§āĻ˛ā§ā§āĻž āĻāĻŋā§ ? Why is water liquid at room temperature ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻĒāĻžāĻ¨ā§ā§° āĻāĻŖāĻŋāĻāĻžāĻŦā§ā§°ā§° āĻŽāĻžāĻā§° āĻāĻāĻ°ā§āĻˇāĻŖ āĻŦāĻ˛ āĻŽāĻ§ā§āĻ¯āĻŽā§ā§āĻž āĻšā§āĨ¤ The force of attraction between water particles is moderate.
11(b). āĻ¸āĻžāĻ§āĻžā§°āĻŖ āĻāĻˇā§āĻŖāĻ¤āĻžāĻ¤ āĻ˛ā§ā§° āĻāĻ˛āĻŽāĻžā§°āĻŋāĻā§ āĻāĻ āĻŋāĻ¨ āĻāĻŋā§ ? Why is an iron almirah solid at room temperature ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻ˛ā§ā§° āĻāĻŖāĻŋāĻāĻžāĻŦā§ā§° āĻāĻ¨āĻā§ āĻ¸āĻā§āĻāĻŋāĻ¤ āĻā§°ā§ āĻāĻāĻ°ā§āĻˇāĻŖ āĻŦāĻ˛ āĻŦā§āĻāĻŋāĨ¤ Iron particles are tightly packed with strong attraction.
12. 273 K āĻāĻˇā§āĻŖāĻ¤āĻžāĻ¤ āĻĨāĻāĻž āĻŦā§°āĻĢā§ āĻāĻā§ āĻāĻˇā§āĻŖāĻ¤āĻžāĻ¤ āĻĨāĻāĻž āĻĒāĻžāĻ¨ā§āĻ¤āĻā§ āĻŦā§āĻāĻŋ āĻ āĻžāĻŖā§āĻĄāĻž āĻā§°ā§ āĻāĻŋā§ Why does ice at 273 K produce more cooling than water at the same temperature ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻŦā§°āĻĢā§ āĻāĻ˛āĻŋāĻŦāĻ˛ā§ āĻ āĻ¤āĻŋāĻ°āĻŋāĻā§āĻ¤ āĻ˛ā§āĻ¨ āĻ¤āĻžāĻĒ āĻļā§āĻˇāĻŖ āĻā§°ā§āĨ¤ Ice absorbs extra latent heat while melting. Science 9th : Ass / Eng
13. āĻāĻ¤āĻ˛āĻž āĻĒāĻžāĻ¨ā§ āĻā§°ā§ āĻĒāĻžāĻ¨ā§ā§° āĻāĻžāĻĒā§° āĻā§āĻ¨āĻā§āĻŦā§ āĻŦā§āĻāĻŋāĻā§ āĻĒā§ā§°āĻŋāĻŦ ? Which causes more severe burns — boiling water or steam ?
āĻāĻ¤ā§āĻ¤ā§° / Ans: āĻĒāĻžāĻ¨ā§ā§° āĻāĻžāĻĒā§ āĻŦā§āĻāĻŋāĻā§ āĻĒā§ā§°āĻŋāĻŦ, āĻāĻžā§°āĻŖ āĻā§āĻžāĻ¤ āĻ˛ā§āĻ¨ āĻ¤āĻžāĻĒ āĻĨāĻžāĻā§āĨ¤ Steam causes more severe burns because it contains latent heat.