Home Geography for Primary Grades · Lesson XIV · Unit 4: Water, air and weather
14. How water is changed to vapor
Goal: Your child knows that heat changes water into an invisible vapor that goes into the air, and sees it happen with wet cloths, puddles and a dish of water.
You'll need
- A damp sponge and a slate, chalkboard or dark tile
- A small plate or saucer of water
- A wet washcloth
- A kettle or pot of water (adult only, for watching)
- A geography notebook (any notebook kept just for these lessons) and a pencil
What's in the book
The lesson asks what happens to the water in a kettle on a hot stove: it is changed to vapor, not destroyed, and the air holds the vapor as a sponge holds water. Warm air can hold more vapor than cold. Then simple observations: a damp slate drying, a wet hand waved in the air, clothes drying on the line, a plate of water in the sun, roads drying after rain, dew vanishing in the morning sun.
The lesson, step by step
Where did it go?
Ask: When water boils in a kettle for a long time, the kettle gets emptier. Where does the water go? Is it gone forever?
The water is changed, but it is not destroyed.
Watch a kettle (adult only)
An adult heats water in a kettle or pot while your child watches from a safe distance.
Safety: steam burns. Your child stays back and never touches the kettle, pot or steam.
SayThe water is turning into vapor, so small and spread out that we cannot see it. It floats away into the air of the room.
A sponge of air
Read:
The air holds the vapor, just as a sponge holds water.
SayWarm air is like a big sponge and can hold more water than cold air.
Disappearing water
Do the book's small experiments: wipe a slate or dark tile with a damp sponge and watch the wet patch vanish. Dip a hand in water and wave it in the air. Where did the water go?
A race to dry
Put a saucer of water in a sunny window and another in a shady corner. Hang one wet washcloth in the sun and one in the shade. Check them later today and tomorrow. Which dries first? Why?
Outdoors
After a rain, notice puddles and wet roads drying up. In the early morning, look for drops on the grass, then look again when the sun is up.
Ask the book's question: Has all the water sunk into the ground?
Why does it rise?
Read the last part: smoke goes up because it is lighter than air.
Ask: Vapor is lighter than air too. What do you think happens to it? (It rises up into the sky.)
Afterwards
Check the saucers each day and mark the water level with a pen on tape until the sunny one is empty.
Answers to the book's problems
The water in the kettle is changed to vapor, which floats in the air; it is not destroyed. The water on a wet slate, a wet hand, clothes on the line, a plate in the sun and muddy streets goes into the air as vapor (some of the street water also sinks into the ground). When the sun warms the air in the morning, the drops on the grass dry up and go into the air. Vapor rises because it is lighter than air.
Worked out for this site from the scan. If a number in your copy differs, trust the book.