NCERT PRACTICE QUESTIONS
1. State similarities and differences between the laboratory thermometer and the clinical thermometer.
Ans.- Similarities -Both are made of glass and consist of long narrow glass tube. At one end both of them have a bulb. Bulbs of both the thermometers consist of mercury. Celsius scale is present in both the thermometer
Differences
Clinical Thermometer | Laboratory thermometer |
Temperature range if 35C to 42C | Temperature range is 10C to 110C |
Used to measure human body temperature | Used to measure temperature in the laboratory |
It has kink which prevents immediate back flow of mercury | It does not have a kink |
2. Give two examples each of conductors and insulators of heat.
Ans.- Conductors are Iron and Copper while insulators are Plastic and rubber.
3.Fill in the blanks :
(a) The hotness of an object is determined by its __________.
(b) Temperature of boiling water cannot be measured by a _____________ thermometer.
(c) Temperature is measured in degree ______________.
(d) No medium is required for transfer of heat by the process of __________.
(e) A cold steel spoon is dipped in a cup of hot milk. Heat is transferred to its other end by the process of ______________.
(f ) Clothes of ______________ colours absorb more heat better than clothes of light colours.
Ans.- (a) temperature. (b) clinical (c) Celsius. (d) radiation.(e) conduction. (f ) dark
4. Match the following :
Ans.-
Column-I | Column-II |
(i) The land breeze blows during | (d) night |
(ii) The sea breeze blows during | (c) day |
(iii) Dark coloured clothes are preferred during | (b) winter |
(iv) Light coloured clothes are preferred during | (a) summer |
5. Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Ans.- Wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing as air gets trapped in-between layer when we wear multiple clothes.
6. Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.
7. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Ans.- In places of hot climate, it is advised that the outer walls of houses to be painted white because white colour reflects back most of the heat that is falls on it as white poorly absorbs heat. This helps in keeping the house cool in warm weather.
8. One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be
(a) 80°C (b) more than 50°C but less than 80°C (c) 20°C (d) between 30°C and 50°C
Ans. - The temperature of the mixture will be between 30°C and 50°C because hot water loses the heat and simultaneously cold water gains heat this keeps the temperature in between high and low.
9. 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.
Ans. - (b) not flow from iron ball to water or from water to iron ball.
10. A wooden spoon is dipped in a cup of ice cream. 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.
Ans.- (d) does not become cold because wood is a bad conductor of heat.
11. 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 stainless steel.
(d) copper is easier to clean than stainless steel.
Ans. - (c) copper is a better conductor of heat than the stainless steel.
Junior Science Topic - Heat. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 7, CBSE syllabus, chapter 04)
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