Winter Science Experiments at Home: Frost, Salt and Snowflakes
By Ahmed, founder
When the weather turns cold, kids stay inside and parents run out of ideas by about 10 a.m. The good news is that winter is full of science, and most of it needs nothing you don’t already have in the kitchen.
Here are three winter science experiments for kids aged 5 to 11. Each one starts with a question, and each one has a real answer that you, the grown-up, can explain with confidence.
1. Can you make frost on a can?
Pack crushed ice into two clean tin cans. Add a few spoonfuls of salt to one, stir, and wait. Within a few minutes, the salted can grows a layer of frost on the outside.
Why it works. Salt makes ice colder than ice alone. A mix of ice and salt can drop to about −21 °C (−6 °F). The outside of the can gets so cold that water vapour from the air lands on it and freezes. The frost didn’t leak through the can. It came out of the air in your kitchen.
What to ask your child: “Where did the water come from?” Most children guess “inside the can.” The comparison with the unsalted can is what proves them wrong, and that’s a fair test in action.
Full instructions, the questions kids ask and an easier version for younger children are in our lesson Can you make frost in a can?
2. Why does salt melt ice?
Put three ice cubes from the same tray on three plates. Sprinkle one with salt, one with sugar and leave one alone. Watch which melts fastest and which makes the biggest puddle.
Then try the classic trick: lay a piece of string across an ice cube floating in a glass of water, sprinkle a pinch of salt on the string and wait about a minute. The string freezes to the cube and you can lift the cube out of the glass.
Why it works. Salt dissolves in the thin film of water on the ice and lowers the temperature at which that water freezes. So the ice melts, which takes heat from its surroundings, and the mixture gets colder. For a moment there’s a cold puddle around the string that refreezes and grabs it.
It also explains why roads are salted in winter. Salt works well down to a certain point, and below that, it stops helping much, which is why salting doesn’t solve everything on the coldest days.
Try it with the lesson Why does salt melt ice?
3. What’s inside a snowflake?
If it’s snowing, put a piece of dark fleece or black felt outside for ten minutes to chill, then catch a few flakes on it and look with a magnifying glass. You’ll see six-sided shapes: plates, columns and branching stars.
Why six? A snowflake is a single ice crystal that grows from water vapour. Water molecules lock together in a hexagonal pattern, so the crystal grows with six sides or six arms. Each arm meets slightly different air as it falls, which is why no two flakes follow the same path, even though they follow the same rules.
No snow where you live? Grow a crystal snowflake on a pipe cleaner overnight in a jar of very hot, salt-saturated water (a grown-up handles the hot water). The lesson What’s inside a snowflake? covers both the snow and no-snow versions.
A note for readers south of the equator or in warm climates: winter in your January is summer’s opposite, so save these for June or July, or use ice from the freezer. The frost-on-a-can experiment works in any season, indoors.
How to get more from these experiments
- Predict first. Ask “What do you think will happen?” and let your child say why, even if it’s wrong.
- Change one thing. Salt versus no salt. Sugar versus salt. One change at a time is the heart of a fair test.
- Write down what you see. A few words or a drawing is enough.
- Finish with “How do you know?” That question turns a fun activity into science.
Where to go next
Every winter experiment above comes from our Winter Science at Home unit, written for parents with the science explained and no science background needed. You can also browse science experiments for kids at home or sign up for three full lessons as printable PDFs, free.