NCERT Solutions Curiosity Chapter 7 .1 Hot or Cold? — Activity 7.1: Let us investigate
Book page 1247 Updated on2026-09-05
Q1.
Write down your predictions. — What will my right hand feel on dipping it in B?
Answer
Prediction: the right hand will feel that the water in B is cool (cold).
Remember what each container holds:
Container
What is in it
Which hand was in it
A
Warm water
Right hand, for 1–2 minutes
B
Tap water
Both hands together, afterwards
C
Ice-cold water
Left hand, for 1–2 minutes
Why it happens: the right hand has been sitting in warm water, so it has become used to warmth. Tap water in B is cooler than the warm water in A, so to that hand B feels cool.
Q2.
What will my left hand feel on dipping it in B?
Answer
Prediction: the left hand will feel that the water in B is warm.
Why it happens: the left hand has been sitting in ice-cold water. Tap water in B is warmer than the ice-cold water in C, so to that hand the very same water feels warm.
So the two hands are placed in one and the same bowl of water at the same moment, and they report two opposite things.
Q3.
Now, conduct the activity and write your observations.
Answer
Observation: the predictions come true. Water in B is a single sample at a single temperature, yet
Hand
Was earlier in
What it feels in B
Right hand
Warm water (A)
Cool
Left hand
Ice-cold water (C)
Warm
Conclusion:Our sense of touch cannot always be relied upon to decide correctly whether a body is hot or cold.
Why it happens: the skin does not sense temperature. It senses the flow of heat between the object and itself. Heat flows out of the warm right hand into the tap water, so that hand says “cool”; heat flows from the tap water into the cold left hand, so that hand says “warm”. Both hands are honest — they are simply answering a different question from the one we asked.
Check it yourself: put a steel tumbler and a woollen cap side by side in the same room. The steel feels colder — yet a thermometer shows both at the same room temperature. Steel simply carries heat away from your hand faster.