Step 1 of 5 · Predict
Before you test: what's your guess?
Almost everything gets smaller and heavier when it freezes. Water is the odd one out — and that's why ice cubes bob at the top of your drink instead of sinking.
“No peeking ahead. Commit to an answer first — being wrong on purpose is how scientists learn fastest.”
What other kids guessed
Step 2 of 5 · Experiment
Test it in your kitchen.
Fifteen minutes, four things you already own. Tap each step as you finish it.
“Do them in order and don't skip the waiting. The melting step is the one that surprises everyone.”
You'll need
- A clear glass of water
- Two ice cubes
- A marker or tape
- Salt (a big spoonful)
Step 3 of 5 · Explain
Here's what's actually happening.
Density is just how much stuff is packed into a space. When water freezes, its molecules lock into a rigid six-sided lattice with gaps — so the same amount of water takes up about 9% more room as ice.
Liquid water
1.00 g/cm³
Molecules slide past each other and fill every gap they can find.
Ice
0.92 g/cm³
A rigid lattice with built-in gaps — same water, more room.
Less dense than the liquid around it means it floats. That is the whole answer.
Step 4 of 5 · Check yourself
Predict the next one.
You drop an ice cube into a glass of cooking oil instead of water. Oil's density is about 0.92 g/cm³ — almost exactly the same as ice. What happens?
“Compare the two numbers before you answer. What does it mean when they're nearly identical?”
Step 5 of 5 · Record it
Write it down properly.
Real scientists don't trust their memory. Print the lab sheet, fill in what you predicted versus what actually happened, and keep it — you'll compare it to Lesson 4.
“Print the lab sheet before you forget what happened. Future you will thank present you.”
Lesson complete!
That's every step of “Why does ice float?” finished. Fern the Fox is impressed.