Ice Fishing with Salt

Ages 5+ with an adult5 minutesMess: Low

Grown-ups: please supervise this experiment the whole time. Read the safety notes first.

Lift an ice cube out of a glass using only a piece of string and a pinch of salt.

WOW FACT

Salt lowers the temperature at which water freezes. That's why gritters spread salt on icy roads in winter.

🧰 What you'll need

Ice cubesFrom the freezer.
✔ You probably have this

A glass of cold water or a saucerTo hold the ice cube.
✔ You probably have this

String or cottonAbout 20 cm is plenty.
✔ You probably have this

Table saltJust a pinch.
✔ You probably have this

✨ Want to go further? (optional)

Kids' chemistry setMore safe experiments about melting, mixing and freezing.
View on Amazon (amazon.co.uk)

Kids' thermometerMeasure how cold the ice and water really get.
View on Amazon (amazon.co.uk)

Children's science experiment bookDozens of easy experiments for rainy days.
View on Amazon (amazon.co.uk)

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What to do

Float an ice cube in a glass of water (or put it on a saucer).
Lay one end of the string across the top of the ice cube.
Sprinkle a pinch of salt over the string where it touches the ice.
Wait about a minute.
Gently lift the string. Can you lift the ice cube?
Try it without salt to compare.

What's going on?

Salt makes the ice start to melt where it lands. That melting takes heat from the water around it, which then refreezes around the string and traps it. It's a cousin of the reason salt is spread on icy roads.

Safety notes

Don't let small children put salt or ice in their mouths.
Very cold ice can stick to skin: handle with dry fingers briefly.