The Fairy-Land of Science · Lecture IV, part 1 · Part 4: Lecture IV: A drop of water on its travels
10. A drop of water goes up into the sky
Goal: Your child can explain that the sun's heat turns water into invisible vapor that rises into the air, and that the vapor cools high up into clouds and falls as rain.
You'll need
- Two saucers, water, and a marker or piece of tape
- A bowl of hot tap water (not boiling) and a cold glass lid or plate from the fridge
- Science notebook and pencils
What's in the book
Pages 73 to 80. Following one drop of water on its travels: a boiling kettle shows that steam is invisible until it cools into "water-dust"; the sun lifts water invisibly from seas and ponds every day; rising air cools and the vapor becomes clouds; and cold winds or cold mountains squeeze the water out as rain.
The lesson, step by step
Hook question
Dip your finger in water and hold up the drop.
Tell me, have you any idea where this drop has been?
Let your child imagine: a cloud? the sea? a river? Buckley says it has been all of these.
Read together
Read pages 73 to 75. Buckley boiled a kettle over a spirit-lamp. Right at the spout there's a clear gap: that is the real steam, invisible. The cloud a little way off is steam that has cooled into tiny drops.
its particles are drawn together again into tiny, tiny drops of water, to which Dr. Tyndall has given the suggestive name of water-dust.
Safety: steam burns badly. Only an adult goes near a boiling kettle. Buckley's spirit-lamps are open flames; we won't use them.
Try it: catch the water-dust
Pour hot tap water into the bowl. Hold the cold lid over it for a minute, then lift it and look underneath: drops! The warm water gave off vapor, and the cold lid turned it back into water.
SayThat's how clouds and rain work.
Try it: water vanishing
Pour the same amount of water into two saucers. Mark the level with tape or marker. Put one in a sunny window and one in a shady spot. Check them every day this week.
Without any fuss or noise or sign of any kind, the water of our earth is being drawn up invisibly into the sky.
From vapor to rain
Read pages 78 to 80. As wet air rises, it spreads out and cools, and the vapor turns to water-dust: a cloud. When a cold wind blows through the cloud, the tiny drops join into big ones, and down comes the rain. Buckley tells of hills in India where 500 inches of rain fell in nine months.
Look up at the clouds as you go home, and think that the water of which they are made has all been drawn up invisibly through the air.
Tell it back and check
Your child tells the drop's journey from the sea to the cloud and back. Then ask:
1. Is steam visible or invisible?
2. What made the drops under the cold lid?
3. Which saucer do you think will dry first?
Draw it
Draw the water cycle as a circle of arrows: sea, sun lifting vapor, cloud, rain, river, back to the sea. Put a little drop with a face traveling round it.
Afterwards
Notice it this week: check the two saucers each day. Watch puddles dry up after rain, and laundry drying on a line.
Tip
Clouds form on tiny specks of dust and salt in the air; the water-dust needs something to gather on. It's a nice extra to share if your child asks why clouds don't form everywhere.
Answers to the book's problems
1. Invisible; the white cloud we see is tiny drops of water. 2. Invisible vapor from the hot water cooled on the cold lid and turned back into drops. 3. The one in the sun, because the sun's heat lifts the water away faster.
Worked out for this site from the scan. If a number in your copy differs, trust the book.