Basic Science Solutions for Class 7 Science Chapter 5 Heat are provided here with simple step-by-step explanations. These solutions for Heat are extremely popular among class 7 students for Science Heat Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of class 7 Science Chapter 5 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class 7 Science are prepared by experts and are 100% accurate.

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When we heat a pan of water, the water boils and at its temperature rises. The energy for this rise in temperature comes from heat. This shows that heat is a form of energy.

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Temperature of a body is the measure of the hotness or coldness of the body. Celsius and Fahrenheit are the scales used to measure temperature.

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We measure the degree of hotness or coldness of a body by measuring its temperature.

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Following are the three changes that heat can cause in any substance:
(a) Heat can change the temperature of a substance.
(b) Heat can expand a substance.
(c) Heat can change the state of a substance.

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Heat  travel through the spoon by conduction.

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We can hold a match while it is burning as we hold only the wooden part of the matchstick. Wood is a bad conductor of heat and does not support transfer of heat through conduction, thus remaining cold enough to be held easily in hand, while its other end is on fire.  

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Heat from the heater transfers to the whole room through radiation eventually rising the temperature of the whole room.

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Heat from the sun reaches the earth by the process of radiation.

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Heat and light, both are forms of energy and both travel in a straight line.

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The flow of heat from the hotter body to the colder body will stop when the temperatures of the two bodies become equal.

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Celsius Scale Fahrenheit Scale
The melting point of ice is taken at 0°C. The melting point of ice is taken at 32°F.
The boiling point of the water is taken at 100°C. The boiling point of the water is taken at 212°F.

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Convection is a process through which heat travels through the water. When a pan of water is heated, the water expands and becomes lighter. The hot water rises up and is replaced by the cooler water from the above. The cooler water is then heated. This process is repeated till all the water in the pan gets heated.

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When radiant energy falls on an object, some of its part is absorbed by the object and some is reflected by the object.
Absorption of the radiant energy depends upon the following:
1. The colour of the object.
2. Nature of the surface.

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(a)

Conduction Radiation
Flow of heat through a medium occurs without the movement of the material. Flow of heat occurs without the help of any material medium.


(b)
Conduction Convection
Flow of heat through a medium occurs without the movement of the medium. Flow of heat through a medium occurs with the movement of medium.

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Sea takes longer to get heated than the land. So, the land is hotter than the sea during the day. The air in contact with the land becomes hot and rises and the cooler air above the sea moves towards the land to replace the hot air. This movement of air from sea towards the land is called sea breeze.
After sunset, the land cools faster than the sea. The air above the sea is warmer than the air above the land. Air above the sea rises and the cooler air above the land moves towards the sea. This is called land breeze.

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The following experiment explains that a gas expands when it is heated:
Take a balloon and a glass bottle. Fit the balloon to the mouth of a glass bottle. Place the bottle in a pan of water. Put the pan over a gas flame and heat it. It is now seen that the balloon gets inflated as the air inside the bottle becomes warm and expands. Also when the bottle is cooled, the balloon gets deflated as the air inside the bottle gets cooler. This shows that gas expands when it is heated.

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(a) It is better to wear light shades in summer because light shades absorb less heat.
(b) Two thin sweaters feel warmer than one thick sweater because the air trapped between the two sweaters acts as an insulator of heat. It does not allow the heat from our body to escape easily.
(c) Handles of utensils are made up of plastic because plastic is a poor conductor of heat. Therefore, heat will not travel through the plastic and the handles will remain cool during cooking. This saves our hand from getting injured from the heat. Metal on the other is a conductor of heat, which helps in transferring heat from the burner flame to the food and helps in cooking the food.

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(a) does not require any medium
Radiation does not require a material medium to travel.



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(b) some metals conduct heat better than others
Some metals conduct heat better than others because they are good conductors of heat than other metals.

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(b) so that the level of mercury does not fall as soon as the thermometer is taken out of the mouth
The capillary tube of  a clinical thermometer has a kink because kink does not allow the level of mercury to fall as soon as the thermometer is taken out of the mouth.

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(c) poor absorber and good reflector of heat
A polished silvery surface is a poor absorber and good reflector of heat.

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(b) good absorber and good emitter of heat
A black body with a rough surface is a good absorber and good emitter of heat.

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(d) evaporation
Sweating causes cooling by evaporation.

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1. True. Water boils at 212 F.
2. False. Clinical thermometer has kink in the capillary tube.
3. True. Liquid expands more than solid.
4. True. The heat from the sun reaches to the earth through radiation.
5. False. Solid is a good conductor of heat than liquid and gas.
6. True. Heat flows in convection by the movement of the substance.
7. False. Transfer of heat by radiation do not need contact between a hot and a cold body.
8. True. Air is a poor conductor of heat.



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