What happens when ice melts and water boils?
Ice, water and water vapour are all the same stuff: water. Heating and cooling change it from solid to liquid to gas, and back.
Solid ice
The ice is a solid. It keeps its own shape. Heat is warming it up towards 0 °C.
Times are not to scale: in real life, boiling water away takes much longer than melting ice. The water level is kept steady so you can cool it back down.
Solids, liquids and gases: questions and answers
Everything around us is a solid, a liquid or a gas. Water is special because we see all three every day: ice is solid, water is liquid, and water vapour is a gas. Heating and cooling change water from one state to another, but it is always water.
What are the three states of matter?
Solid: keeps its own shape, like ice or a rock. Liquid: flows and takes the shape of its container, like water or juice. Gas: spreads out to fill any space, like the air or water vapour.
Why does ice melt?
When ice gets warmer than 0 °C, it takes in heat and turns from a solid into a liquid. That change is called melting.
How does water turn back into ice?
When water is cooled to 0 °C and keeps losing heat, it turns from a liquid into a solid. That is called freezing. A freezer is about −18 °C, so water freezes there.
What happens when water boils?
When water is heated to 100 °C (at sea level), bubbles of water vapour form inside it and rise to the top. The vapour escapes into the air. That is boiling.
Is steam the white cloud above a pan?
Not quite. Real water vapour is invisible. The white mist you see is made of tiny drops of liquid water that form when the vapour cools in the air.
Is melted ice still water?
Yes. Ice, liquid water and water vapour are all made of the same water particles. Only the way the particles are arranged and how much they move changes.
What the 3D model shows
The model shows a steel pan of nine ice cubes on a black hob. Press Play and the hob ring glows to show heating. The ice cubes shrink as they melt and liquid water fills the bottom of the pan, with the last pieces of ice floating. The thermometer reading stays at 0 °C until the ice has gone, then rises to 100 °C. At 100 °C bubbles rise through the water and white mist drifts above it. Then the model cools: bubbles stop, the water cools to 0 °C, and it freezes back into ice. A small zoom-in panel shows a particle model: in ice the particles sit in rows and wiggle in place; in liquid water they slide past each other; in water vapour they fly far apart.
Common mix-ups
- “Bubbles in boiling water are air.” They are mostly water vapour, the gas form of water.
- “Steam is the white cloud.” Water vapour is invisible; the white cloud is tiny water droplets.
- “Melting ice turns into a different substance.” It is still water. Melting is a change of state, not a new material.
- “Water keeps getting hotter while it boils.” At normal air pressure, boiling water stays at about 100 °C, however strong the heat.
Remember
Heating can melt ice and boil water; cooling can turn it back. Solid, liquid or gas, it is still water.
For grown-ups: things to ask
- Before pressing Play, ask: “What will happen to the ice first? Will the water level go up or down?”
- Pause on “Melting” and ask: “Why do you think the temperature stops at 0 °C?”
- Try it safely at home: put an ice cube on a plate and time how long it takes to melt, then put the water back in the freezer.
Going deeper (ages 9–11)
Why does the temperature stop rising while ice melts?
While ice is melting, the heat goes into breaking the ice’s fixed pattern of particles instead of warming it. So the temperature stays at 0 °C until all the ice has melted. The same thing happens at 100 °C while water boils.
Why does ice float?
When water freezes, its particles lock into an open pattern that takes up more space. That makes ice a little less dense than liquid water, so it floats with most of it under the surface.
What is the difference between boiling and evaporation?
Evaporation happens at the surface of water at any temperature, which is why puddles dry up. Boiling happens all through the water when it reaches its boiling point, which is why bubbles form inside it.
How do particles move in each state?
In a solid, particles are packed tightly in a pattern and vibrate in place. In a liquid, they are still close together but can slide past each other. In a gas, they are far apart and move quickly in all directions.
What this model simplifies
- Real melting and boiling take different amounts of time: boiling all the water away takes far more heat than melting the ice. The timings here are squeezed so you can see every stage.
- In a real open pan, boiling water slowly disappears into the air. Here the water level stays steady so the model can cool back down.
- Freezing is shown in the same pan for simplicity. In real life you would put the water in a freezer.
- Water boils at 100 °C at sea level. High up a mountain, it boils at a lower temperature.
- The particle picture is a simple model. Real water particles are far too small to see, and there are trillions of them.
Sources
- NASA Science for Kids: What is the water cycle? (water as solid, liquid and gas)
- OpenStax Physics: Phase change and latent heat
- NSTA: What’s in the bubbles?
- Science Learning Hub: Hidden heat
Last updated 10 November 2026. Made by Akhil Paul. Interactive lessons are free to use.