Heat
Heat - NCERT Guide Science Class 7
Q1: State similarities and differences between the laboratory and clinicalthermometer.
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Ans:
Similarities:
1. Both consist of a long, narrow, uniform glass tube.
2. Both have a bulb containing mercury at the end of the tube.
3. Both are marked with Celsius scale on the glass tube.
Differences:
1. A clinical thermometer reads temperature from 35OC to 42OC, while a laboratory thermometer ranges between
–10OC to 110OC.
2. Clinical thermometer has a kink near the bulb while there is no kink in laboratory thermometer.
Q2: Give two examples each of conductors and insulators of heat.
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Ans:
Conductors of heat: copper, iron.
Insulators: wood, paper, plastic.
Q3:Fill in the blanks:
- The hotness of an object is determined by its _____________.
- Temperature of boiling water can not be measured by a _________thermometer.
- Temperature is measured in degree ___________.
- No medium is required for transfer of heat by the process of _______.
- A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of _________.
- Clothes of __________ colours absorb heat better than clothes of light colours.
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Ans:
(a) temperature, (b) Celsius, (c) conduction, (d) clinical, (e) radiation, (f) dark
Q4: Match the items in column I with those in column II:
| Column I |
Column II |
- Land breeze blows during
- Sea breeze blows during
- Dark coloured clothes are preferred during
- Light coloured clothes are preferred during
|
- Summer
- Winter
- Day
- Night
|
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Q5: Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
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Ans:
Wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing because of the air trapped between two layers of clothes. This layer prevents the flow of the heat from our body to the cold surroundings and keeps our body relatively warmer.
Q6: In places of hot climate it is advised that outer walls of houses be painted white. Explain.
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Ans:
It is because the white colour reflects most of the heat that falls on it. Hence, the outer walls of the houses in the places of hot climate are advised to paint with white colour so that most of the heat falling on these walls would be reflected which will help in keeping the houses cool.
Q7: One liter of water at 30'C is mixed with one liter of water at 50'C. Thetemperature of the mixture will be:
- 80'C
- more than 50'C but less than 80'C
- 20'C
- between 30'C and 50'C
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Q8: An iron ball at 40'C is dropped in a mug containing water at 40'C. The heat will
- flow from iron ball to water
- not flow from iron ball to water or from water to iron ball
- flow from water to iron ball
- increase the temperature of both.
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Q9: A wooden spoon is dipped in a cup of ice cream. Its other end
- becomes cold by the process of conduction.
- becomes cold by the process convection.
- becomes cold by the process of radiation.
- does not become cold.
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Q10: Stainless steel pans are usually provided with copper bottoms. The reason for this could be that
- copper bottom makes the pan more durable.
- such pans appear colourful.
- copper is better conductor of heat than the stainless steel
- copper is easier to clean than the stainless steel
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NCERT (CBSE) Science Class 7 Heat - Study Material
(Notes and Additional Important Questions)
- Give the names of any three kinds of thermometers.
- Which metal is used in the bulb of thermometer?
- hat is the Wunit of temperature?
- What is the range of clinical thermometer?
- By which method we get heat from the sun?
- What kind of cloth we prefer in summer?
- What are conductors?
- State whether following statements are true or false:
- Our sense of touch about hotness or coldness is not always reliable.
- Normal temperature of human body is 98.6'C
- In all cases heat flows from a hotter object to a colder object
- Water at higher temperature feels hotter.
- Marking on clinical thermometer is from 0'C to 100'C.
- Shinning thread in thermometer is the column of mercury
- The materials which allow heat to pass through them easily are calledconductors.
- Water and air are good conductors of heat.
- Woolen clothes keep us warm during winter.
- The maximum and minimum temperature of the day is measured by a laboratory thermometer.
- Celsius is the SI unit of temperature.
- Conduction is the method of transfer of heat in gases.
9. Fill in the blanks:
- Temperature is the measure of _________ of an object.
- The thermometer used to measure human body temperature is called __________ thermometer.
- The normal temperature of human body is ___________'C.
- A ___________ near the bulb of a clinical thermometer prevents mercury level from falling of its own.
- The water and air are ___________ conductors of heat.
- All hot bodies radiate ______________.
- Wool is a ____________ conductor of heat.
