One ice cube, three faces
An ice cube (solid) melts into a puddle (liquid) on a hot day, and the puddle vanishes into the air (gas) by afternoon. It's the same water wearing three different outfits depending on how warm it is.
Matter comes in three states
Everything around us is matter, and most matter is a solid, a liquid, or a gas. A solid keeps its shape, like a rock. A liquid takes the shape of its container and can be poured, like water. A gas spreads out to fill all the space it can, like the air in a balloon.
Heat can change the state
Ice (solid) melts into water (liquid) when it warms up, and water boils into steam (gas) when it gets hot enough. Cooling reverses the change.
🧊 ice → 💧 water → ☁️ steam, as it gets warmer.