The Fairy-Land of Science · Lecture IV, part 3 · Part 4: Lecture IV: A drop of water on its travels
12. Snowflakes, ice, glaciers, and the salty sea
Goal: Your child can say that snowflakes are six-pointed crystals, that water swells when it freezes, that icebergs float mostly under water, and why the sea is salty.
You'll need
- A small plastic cup of water and a marker
- A freezer
- A clear glass of water and an ice cube
- Black paper or a dark cloth (if it is snowing)
- Paper and scissors for a paper snowflake
- Science notebook and pencils
What's in the book
Pages 89 to 98. Snowflakes as six-pointed crystal stars; looking at melting ice with a magnifying glass; why ice takes more room than water and bursts pipes; snow pressed into glaciers and icebergs; hard water; why the sea is salt; and the end of the drop's travels.
The lesson, step by step
Hook question
SayEvery snowflake is different. But they all share one thing. Can you guess what?
Then read page 89.
you will see that the snow-flakes are not mere lumps of frozen water, but beautiful six-pointed crystal stars
Try it: ice needs more room
Fill the plastic cup about half full of water and mark the level. Put it in the freezer. Tomorrow, look: the ice is higher than the mark.
And this leads us to notice that ice always takes up more room than water, and that this is the reason why our water-pipes burst in severe frosts
Now drop the ice cube into the glass of water. It floats, with most of it under the water.
SayThat's why icebergs are so dangerous to ships. Most of the iceberg is hidden.
Make a six-pointed snowflake
Fold and cut a paper snowflake with six points. (Fold a circle in half, then fold it into thirds, then cut shapes.) If it is snowing, catch flakes on black paper and look closely with a magnifying glass before they melt.
Rivers of ice
Read or tell pages 92 to 94. Snow on high mountains piles up and gets squeezed into clear ice that creeps slowly downhill.
Then we have what is called a "glacier," or river of ice
In Greenland the glaciers reach the sea and pieces snap off as icebergs.
Why is the sea salty?
Read or tell pages 95 to 97. Rivers carry tiny bits of salt and lime from the land, too small to see. The sun lifts only pure water out of the sea, so the salt is left behind.
If you like, leave a saucer of salty water in the sun for a few days (instead of boiling sea water on the stove, as Buckley suggests).
Tell it back and check
Your child tells the whole journey of the drop from Lecture IV: sea, vapor, cloud, rain or snow, river or glacier, back to the sea.
Ever onwards it goes, up and down, and round and round the world, taking many forms, and performing many wonderful feats.
Then ask:
1. How many points does a snowflake have?
2. Why do water pipes burst in a hard frost?
3. Why is the sea salty but rain is not?
What we know now
Buckley guessed that the tiny bits of water have two different ends, like her magnets, and line up into crystals. She was close: each water molecule has a slightly positive side and a slightly negative side, and these pull water into its six-sided pattern when it freezes.
Afterwards
Notice it this week: check the cup in the freezer, ice cubes floating in drinks, and (in winter) frost patterns and snowflakes.
Tip
An ice cube floats with about nine-tenths of itself under water. Look at it from the side of the glass to see.
Answers to the book's problems
1. Six. 2. Water takes up more room when it freezes, so the ice pushes the pipe until it cracks. 3. Rivers carry salt into the sea, and the sun lifts out only pure water, so the salt stays behind; rain is made from that pure water.
Worked out for this site from the scan. If a number in your copy differs, trust the book.