Question

plz ans for questions 7,8,9,10,11,12,13 plz friends urgent
​

Answer 1

Explanation:

woolen clothes does not allowed air to pass through it Ice and melting stop

Answer 2

Answer :-

Q. 7

1. In summer, the ice is kept wrapped in a woolen cloth. The air filled in the fine pores of the woolen cloth is the good insulator of heat.
2. A tea pot is made with woolen handel because wood is poor conductor of heat . hence when tea pot will be hot then also it wil be easy to handel .
3. The fuel is saved when it is blackened from the bottom and polished from side because dark colour is good conductor of heat and maximum heat produce due to burning of fuel is absorb by the dark colour so less energy is required.
4. We prefer two thin blanket rather than one thik blanket because two thin blanket contain a layer of air in between them and we know air is poor conductor of heat so the heat of our body does not get wasted in the air as it happen by a thik blanket .
5. Coastal areas have moderate temperature because the land absorbs and radiates heat much faster than sea. So, during the day cool air from sea rush towards the land and during night the opposite happen so cool air from the land rush towards sea.

Q. 8 When we touch ice we feel cool because the ice absorbs the heat from our body where it is being placed and turns into liquid, the heat absorb by ice from body ,make it cool.

Q. 9 The container painted white from outside will get cooler fast then the container painted black because the black colour will absorb heat whereas white colour will reflect the heat .As dark colour is good condoctor

of heat so it will take time to water to get cool than other container

Q. 10

1. conduction: Ice cooling down your hand
2. convection :Hot air rising, cooling, and falling
3. Radiation :Heat from a lightbulb

Q. 11

1. Good conductor :- Copper,mercury,water,iron,brass,stainless steel
2. Bad conductor :- leather,wool,air,brick,straw,card board,plastic

Q. 12 The water in a container gets heated due to convection process in this way -

• When the container gets heated then the water in the bottom of container absorb heats and get warm .
• When the water in bottom get heated then the cold water from the top move down and hot water from container move up
• Then this thing happen again and again till the whole water get heated.

Q. 13 Four reason to use mercury in thermometer -

1. It’s used in thermometers because it has a high coefficient of expansion.
2. It is used in thermometer because it does not stick to side of glass tube .
3. It is used because it show even very small change in temperature .
4. It is used because it has high density and high specific heat