CBSE NCERT Solutions for Class 7 Science Chapter 4
Heat: Question – Answers
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7 Science Chapter 4: Heat
Important Questions with Answers
- Paheli and Boojho measured their body temperature. Paheli found her’s to be 98.6 °F and Boojho recorded 37°C. Which of the followng statement is true?
(a) Paheli has a higher body temperature than Boojho.
(b) Paheli has a lower body temperature than Boojho.
(c) Both have normal body temperature.
(d) Both are suffering from fever.
- 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 surrounding.
- 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.
- Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
- Why is it advised not to hold the thermometer by its bulb while reading it?
- To keep her soup warm Paheli wrapped the container in which it was kept with a woollen cloth. Can she apply the same method to keep a glass of cold drink cool? Give reason for your answer.
- You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so?
- In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object. What is the reason for this rise in the level of mercury?
- 1 (c)
- 2 (b)
- 3 (a)
- 4. They must use some insulating material like, sack, saw dust, newspaper, etc. to cover the ice.
- 5. If we hold a thermometer by its bulb, the mercury in the bulb will expand due to our body temperature.
- 6. Yes. Wool is poor conductor of heat.
- 7. The jerk to the thermometer will allow the mercury in or above the kink to flow into the bulb so that the mercury level is below normal temperature.
- 8. Mercury expands when heated. Hence, it rises in the capillary tube.