Paheli Boojho Heat Science Class 7 Chapter 4 Answer

Paheli Boojho Heat Science Class 7 Chapter 4 Answer

Question 1: Why do our hand feel different to touch the object which has the same temperature.

Answer: Hot and cold are relative terms. If we are in AC and go outside in the sun, then we will feel hot. However, if we are in shadow and go out in the sun, then we will feel lesser heat than what we felt when we move from AC to outside.

A similar thing happens when we put hands in different solutions one by one. If we put one hand in hot water and another in cold water, then we put bot hands in mixed water first hand will feel cold while the later hand will feel warm. See Activity 4.1.

Question 2: Fahrenheit scale or Celsius scale?

Answer: Our average body temperature is 98.6 ºF or 37ºC. Both indicate the same temperature. Fahrenheit scale is an old scale for measuring the temperature. Now we use celsius scale.

Question 3: Paheli measured her body temperature. She got worried as it was not precisely 37°C.


Body temperature varies from person to person. It may be slightly higher for some people and maybe lower for someone. In a population, the average temperature is 37°C. We take this as a reference. Unless there is a significant variation like 39°C, 40°C, we should not worry.

Q4. Boojho got a naughty idea. He wanted to measure the temperature of hot milk using a clinical thermometer. Paheli stopped him from doing so.

Answer: A clinical thermometer can measure only between 35 to 42°C. Beyond 42 its mercury will not move further and the boiling milk may even break the thermometer bulb or glass. So, Paheli did goodby stopping him from doing so.

Q.5 page 39.

Boojho now understands why a clinical thermometer cannot be used to measure high temperatures. But still wonders whether a laboratory thermometer can be used to measure his body temperature.

In mercury thermometer we need to shake it to move down the mercury level. Laboratory thermometer however, doe not need any shake. It brings down its own mercury level by itself. So, we can not use a laboratory thermometer in measure our body temperature.

Note: A lab thermometer can measure -10 to 110°C temperature.

See also: Paheli Boojhoo answer chapter 2 Nutrition in Animals.

Activity Explanation chapter 4 Heat.

Paheli Boojho Heat Science Class 7 Chapter 4 Answer

Ref: NCERT Science chapter 4.

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