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CBSE 7th Standard Science Heat Important Questions And Answers Study Material - QB365 Set D

Published on: 31/10/2025

Question Set D

CBSE 7th Standard Science Heat Important Questions And Answers Study Material - QB365

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Std: 7th Standard CBSE - Science

chapter: Heat - Important Questions And Answers

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Questions:

Generic 3

6 x 3 = 18

Explain the reason for the shiny reflectors of room heaters.

Observe the picture given in figure. Water is being boiled in a pan of wide base.
(a) Which position P or T will feel warmer?
(b) Fill up the boxes P and T to indicate the mode of flow of heat to the hand.

One litre water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be
(a) 80⁰C
(b) more than 50°C but less than 80⁰C
(c) 20°C
(d) between 30°C and 50°C

Look at the figure, mark where the heat is being transferred by conduction, by convection and by radiation.

Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

Give two examples each of conductors and insulators of heat.

Multiple Choice Question

5 x 1 = 5

A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because

(a)

friction between the layers of newspaper produces heat

(b)

air trapped between the layers of newspaper is a bad conductor of heat

(c)

newspaper is a conductor of heat

(d)

newspaper is at a higher temperature than the temperature of the surroundings

A marble tile would feel cold as compared to a wooden tile on a winter morning because the marble tile

(a)

is a better conductor of heat than the wooden tile

(b)

is polished while wooden tile is not polished

(c)

reflects more heat than wooden tile

(d)

is a poor conductor of heat than the wooden tile

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

(a)

copper bottom makes the pan more durable

(b)

such pans appear colourful

(c)

copper is a better conductor of heat than the stainless steel

(d)

copper is easier to clean than the stainless steel

10.

A wooden spoon is dipped in a cup of icecream, then its other end

(a)

becomes cold by the process of conduction

(b)

becomes cold by the process of convection

(c)

becomes cold by the process of radiation

(d)

does not become cold

11.

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

(a)

flow from iron ball to water

(b)

not flow from iron ball to water or from water to iron ball

(c)

flow from water to iron ball

(d)

increase the temperature of both

Generic 2

6 x 2 = 12

12.

The mercury does not fall or rise in a clinical thermometer when taken out of the mouth. Explain why

13.

A circular metal loop is heated at point O as shown in figure.
(a) In which direction, would heat flow in the loop.
(b) In which order, the pins at points P, Q and R fixed with the help of wax fall if points , P, Q and R are equidistant from each other?

14.

A laboratory thermometer A is kept 7 cm away on the side of the flame while a similar thermometer B is kept 7 cm above the flame of a candle as shown in figure. Which of the thermometers A or B will show a greater rise in temperature? Give reason for your answer.

15.

To keep her soup warm, Paheli wrapped the container in which it was kept with a woollen clothes. Can she apply the same method to keep a glass of cold drink cool? Give reason for your answer.

16.

The radiators in cars are painted black. Explain why.

17.

Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.

Generic 5

3 x 5 = 15

18.

Last Sunday, Pooja on her week off entered in her kitchen to cook rice for her family in lunch time. The moment she put fry pan on the gas stove and lighted it through the matchstick, all of sudden her 5 years small daughter entered into the kitchen and tends to touch the hot fry pan. At the same time, Pooja saw her and pushed her away from the hot fry pan. In this way, she saved her child.
(a) Explain why do the fry pan are provided with the plastic handles?
(b) Mention the values represented by Pooja here towards her 5 years small daughter.

19.

Prove with the help of an experiment that heat radiation can travel through vacuum.

20.

Explain the differences between heat and temperature.

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Answers Key:

Generic 3

6 x 3 = 18

Since, the shiny surface absorbs very little heat due to which the reflectors reflect all the heat which makes the room heaters more effective. So, due to this reason, room heaters have shiny reflectors.

(a) As in the given diagram, position P will feel warmer because of heat, air rises.
(b) The flow of heat to P is a convection process and flow of heat to T is radiation.

Temperature of mixture is in between 30°C to 50°C because water at 50°C losses some heat and water at 30°C gains some heat.

(i) Heat is being transferred in the steel vessel by conduction.
(ii) Heat is being transferred from vessel to water by convection.
(iii) Heat is being transferred from vessel to surroundings by radiation.

Wearing more number of clothes makes air gap which do not allow heat to pass out but in case of one thick cloth it is not as such, so we should wear more layers of clothing during winter to keep us warmer.

Examples of conductors are metal and steel and examples of insulators are wood and plastic.

Multiple Choice Question

5 x 1 = 5

(b)
air trapped between the layers of newspaper is a bad conductor of heat

(a)
is a better conductor of heat than the wooden tile

As copper is a better conductor of heat than the stainless steel. So, stainless steel pans are usually provided with copper bottom.

10.

It does not become cold because it is an insulator.

11.

As heat can only flow from higher temperature to lower temperature. Thus, the heat will not flow from iron ball to water or vice-versa.

Generic 2

6 x 2 = 12

12.

Because of the kink present in the thermometer, the mercury does not fall or rise.

13.

(a) Heat will flow in both the directions from O to P and from O to R.
(b) First of all pin at P and R will fall simultaneously after that pin at Q will fall.

14.

Thermometer B will show a greater rise in temperature because heated-air above the candle risesimmediatly and increase the temperature of bulb of thermometer B quite greater than A.

15.

Yes, she can apply the same method to keep a glass of cold drink cool because wool is a thermal insulator, and it cannot allow to heat pass through it.

16.

Since, the black bodies are better radiators, so due to this reason, radiators in cars are painted black.

17.

As we know that jute sacks is thermal insulators, it helps ice not to be melt immediately. So, shopkeepers used to cover ice blocks with jute sacks.

Generic 5

3 x 5 = 15

18.

(a) As we know that plastic is a bad conductor of heat which does not allow the heat to pass through itself. So, heat from the fry pan does not flow to the handle due to which we can hold it easily. So that's why, the fry pans are provided with the plastic handles.
(b) The value showed by Pooja here is a great concern and careness towards her five years old small daughter.

19.

First of all, take a flat bottom flask and fix a rubber stopper having two holes in the mouth of the flask. Shift a thermometer through one hole and a glass tube with stopper through the other hole. Now, with the help of a vacuum pump, remove the air from the flask and try to record the temperature from the thermometer. Put a flask in the bright sunlight and we will observe that the thermometer records a rise in temperature. So, on this basis, we can say that this experiment proves that the heat radiation can travel through vacuum.

20.

The differences between heat and temperature are given as below

Heat	Temperature
It is a form of energy which flows from one body to another when there is a difference in temperature between the objects.	It is the thermal condition of a body that indicates whether or not and in which direction, heat will flow from one body to the other.
It is equal to the sum of internal energies of the molecules of a body.	It is proportional to average kinetic energy of the molecules of the body.
As a heat between two bodies, total amount of heat of two bodies remains unchanged.	As a conclusion of exchange of heat between two bodies sum of their temperatures before and after exchange is not same.
SI unit of heat is joule (J).	SI unit of temperature is kelvin (K).