NCERT Solutions for Class 5th The World Around Us Chapter 4 Let Us be Cool! — Activity 3
Book page 62 Updated on2026-09-19
Q1.
Take two tiles or stones, paint one black and the other white. Keep them under the Sun. After a while, touch each of them and feel the difference in their temperature. Which one felt cooler?
Answer
The white tile felt cooler. The black tile felt distinctly hot — hot enough that you take your hand off quickly.
How to do it
Take two tiles, or two flat stones, of the same size and the same kind.
Paint one fully black and the other fully white. Let the paint dry completely.
Put both in the open Sun, side by side, on the same surface. Both must get exactly the same sunlight.
Wait about 20 to 30 minutes.
Touch the white one first, then the black one. Touch quickly, with the back of your fingers.
Tile
How it feels after 30 minutes in the Sun
Sample thermometer reading
White tile
Warm, but you can rest your hand on it
about 42 °C
Black tile
Clearly hot; you pull your hand away
about 55 °C
Difference
The black one is much hotter
about 13 °C
Your readings will not be exactly these. They depend on the month, the time of day and how strong the sunlight is. The black tile will always be the hotter one.
Same Sun, same time, same stone — only the colour is different, and that is enough.
Why it happens: Sunlight carries heat. A black surface absorbs it — it takes almost all the heat in, so the tile gets hot. A white surface reflects it — it throws most of the heat back, so less heat stays in the tile and it remains cooler. That is also why white looks bright: it is sending the light back to your eyes.
You already knew this: think of standing barefoot on a black tar road at noon, and then on a white marble floor. Think also of why people wear white or light-coloured clothes in the Indian summer and dark ones in winter.