Class 7 Science Chapter 4 Heat

NCERT Solutions Class 7 Science Chapter 4 Heat

Class 7 Science Chapter 4 Heat Question Answer by online-shiksha

Q1 : State similarities and differences between the laboratory thermometer andthe clinical thermometer.

Similarities:

Both thermometers have long narrow glass tubes.

Both thermometers have mercury in their bulbs.

Differences:

 Clinical thermometers range from 35°C to 42°C laboratory thermometers range from -10°C to 110°C. Clinical thermometers are used to check the body’s temperature Lab thermometers cannot measure human body temperature. clinical thermometers that can be tilted. Laboratory thermometers are generally upright while reading the temperature

Q2 : Give two examples each of conductors and insulators of heat.

Two examples of conductors of heat are:  Aluminium &  Iron

Two examples of insulators of heat are: Wood & Plastic

Q3 : Fill in the blanks:

1. The hotness of an object is determined by its __ __.
2. Temperature of boiling water cannot be measured by a ____ thermometer.
3. Temperature is measured in degree ___ _.
4. No medium is required for transfer of heat by the process of ___ _.
5. A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of __ _ _.
6. Clothes of ___ _ colours absorb heat better than clothes of light colours.

1. Temperature
2. Celsius
4. Conduction
5. Dark

Q4 : Match the following:

 1. Land breeze blows during a. Summer 2. Sea breeze blows during b. Winter 3. Dark coloured clothes are preferred during c. Day 4. Light coloured clothes are preferred during d. Night

1.  Night  , 2. Day  , 3. Winter  , 4. Summer

Q5 : Discuss why wearing more layers of clothing during winters keeps us warmer than wearing just one thick piece of clothing.

In the winter, wearing more layers of clothing keeps us warmer than wearing one piece since air gets trapped between them. Since air is an insulator of heat, it keeps us warm and prevents the body from losing heat. Layers of clothing keep us warm.

Q7 : In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

In hot climates, it is recommended that the outer walls of houses be painted white because a light colour like white reflects back the majority of the heat that falls on it. As a result, light colours tend to keep the house cool.

Q8 : One litre of water at 30°C is mixed with one litre 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) The temperature of the mixture will be between 30°C and 50°C.

Q9 : 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.

(b)not flow from iron ball to water or from water to iron ball [becoz both has same temperature]

Q10 : 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

Q11 : 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 colourful.
3. copper is a better conductor of heat than the stainless steel.
4. copper is easier to clean than the stainless steel.

Answer : (c) copper is a better conductor of heat than stainless steel.

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