NCERT Solutions Curiosity Chapter 8 Extended activities and projects — Learning further

Book page 162 Updated on2026-09-05

Q1.

Wet one hand with water and leave the other dry. Blow air across both hands and feel the cooling effect. Find out the reasons for it.

Answer

What you feel: the wet hand feels distinctly cold while you blow on it; the dry hand feels almost nothing, at most a slight breeze. Stop blowing and the difference becomes smaller. Wet the hand with spirit instead of water and the chill is even sharper.

The reason:

The air you blow out is at about 37 °C — that is your body temperature. It is warmer than the room, not colder. So the coolness cannot be coming from the air itself.
On the wet hand, the moving air sweeps away the humid layer just above the skin and speeds up evaporation.
Evaporating water needs heat, and it takes that heat from your skin.
Your skin loses heat, and you feel cold.
The dry hand has no water on it, so there is nothing to evaporate and no heat is taken away.

Blowing on a wet hand → faster evaporation → heat taken from the skin → the hand feels cold
Blowing on a dry hand → no evaporation → almost no cooling

Why this little experiment is so valuable: it settles the question that puzzles most people — a fan does not blow cold air; it makes the moisture on our skin evaporate. The dry hand is the control, and it is the control that proves the point.

Try This too: wet one hand and hold it still, then wave it about. The waving hand feels colder — proving that air movement is what speeds evaporation up.

Q2.

Make a game to navigate through different states of water and water related concepts to reach the finish line. Challenge cards with questions related to water cycle, evaporation, condensation, etc., can be some game elements.

Answer

Make it as a snakes-and-ladders style board — it is easy to draw and the science fits it perfectly.

What you need: a chart paper board of 40 squares, one die, a token for each player, and about 25 challenge cards made from half a postcard each.

How to build the board:

Square 1 is OCEAN and square 40 is BACK TO THE OCEAN — because the water cycle has no true end.
Mark some squares as stages: puddle, wet clothes, air, cloud, hailstone, mountain snow, glacier, river, lake, groundwater, well, matka, tap.
Draw an up arrow (a "ladder") for a change that lifts water into the sky — evaporation, a hot sunny day, a strong wind, a wide open plate.
Draw a down arrow (a "snake") for a change that brings water down — condensation, rain, hail, snow, freezing, a very humid day.
Mark about eight squares with a "?". Landing there means you must draw a challenge card.

Sample challenge cards (write the answer on the back):

Card	Answer	Reward / penalty
Name the change gas → liquid	Condensation	Move 3 forward
At what temperature does ice melt?	0 °C	Move 3 forward
At what temperature does water boil?	100 °C	Move 3 forward
Give one difference between evaporation and boiling	Evaporation happens at any temperature and only from the surface; boiling happens at 100 °C throughout the liquid	Move 4 forward
Why does a matka keep water cool?	Water seeps through the pores and evaporates, taking heat away	Move 3 forward
Why do clothes dry slowly on a rainy day?	The air is already humid	Move 3 forward
What do water droplets condense around, high in the sky?	Dust particles	Move 4 forward
You left the tap running while brushing	—	Go back 4 squares

What makes the game teach and not just entertain: the arrows are not random. Every ladder is a change that needs heat to be supplied and every snake is a change that needs heat to be removed. After three or four rounds the players stop having to think about it — which is exactly the point.

Q3.

Discuss with your teacher and act out the stages of the water cycle through a role-playing activity in your school assembly.

Answer

A role play works best if each stage of the cycle has its own character, its own line and its own simple prop. Here is a plan for a five-minute assembly item.

Character	Simple costume or prop	Line to say
Sun	A yellow cardboard disc with rays	"I am the Sun. I give the heat that starts the whole journey."
Water drops (4–5 children in blue)	Blue dupattas or blue paper caps	"We live in the ocean. The Sun warms us, and up we rise!" (they rise on tiptoe and move upward)
Evaporation	An upward arrow on a placard	"I am evaporation. I turn liquid water into invisible water vapour — at any temperature, even in your classroom."
Dust particle	A small grey cap	"I am tiny, but without me the droplets would have nothing to gather on."
Condensation	A downward arrow placard	"High up it is cold. I turn the vapour back into tiny droplets." (the water drops crowd around the dust particle)
Cloud	Cotton wool stuck on card, held overhead	"Together, all these droplets are me — a cloud!"
Rain, Hail and Snow	Blue, white and silver ribbons	"We are heavy now. Down we come as rain, as hail, as snow!" (drops crouch and move down)
River	A long blue cloth held by two children	"I carry them across the land, back to the sea." (drops walk under the cloth)
Groundwater	A brown sheet held low	"Some of them soak into me and wait underground, feeding wells and springs."
Narrator	—	"And the journey begins all over again. This never-ending circulation is the water cycle."

How to close it: all the characters stand in a circle, join hands and turn once, to show that the cycle has no beginning and no end. The narrator ends with a line the whole school can repeat — "No new water is ever made. Save every drop."

Tip: Discuss with your teacher first, rehearse twice, and keep every line short. Draw a large water-cycle chart to hold up behind the actors so that the audience can follow the stages while they watch.

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