NCERT Class VII Science Solutions: Chapter 4 – Heat Part 3

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Question 7:

In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Answer:

In places of hot climate it is advised that the outer walls of houses be painted white because white colour reflects most of the heat that falls on it or we can say it absorbs less amount of heat. Therefore, the temperature inside the house does not increase very much.

As showing in images is a result for walls of houses be pain …

Walls of Houses be Painted White

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Question 8:

One liter of water at 30°C is mixed with one liter of water at 50°C. The temperature of the mixture will be

  1. 80°C

  2. more than 50°C but less than 80°C

  3. 20°C

  4. between 30°C and 50°C

Answer:

D. between 30°C and 50°C

Question 9:

An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will

  1. Flow from iron ball to water.

  2. Not flow from iron ball to water or from water to iron ball.

  3. Flow from water to iron ball.

  4. Increase the temperature of both.

Answer: B

The heat will not flow from iron ball to water or from water to iron ball as both the substances have same temperature.

So, when an iron ball at is dropped in a mug containing water at there will be no transfer of heat between the two. This is because the iron ball and the water in the mug are in thermal equilibrium.

Question 10:

A wooden spoon is dipped in a cup of ice cream. Its other end.

  1. Becomes cold by the process of conduction.

  2. Becomes cold by the process of convection.

  3. Becomes cold by the process of radiation.

  4. Does not become cold.

Answer:

D. Does not become cold.

Question 11:

Stainless steel pans are usually provided with copper bottoms. The reason for this could be that

  1. Copper bottom makes the pan more durable.

  2. Such pans appear colorful.

  3. Copper is a better conductor of heat than the stainless steel.

  4. Copper is easier to clean than the stainless steel.

Answer:

D. Copper is a better conductor of heat than the stainless steel.