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🌡️ Heating, Cooling, and Changing State

Heat it up or cool it down and matter can change! Discover melting, freezing, boiling, and condensing, and see how water does all four.

lessons

~20 min

to learn

🔬 Science

subject

Ages 6–12

level

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What you’ll learn

Heating Changes StateExplain melting and boiling as changes caused by heating, and understand melting points.Heating can change the state of matter. Melting turns a solid into a liquid, like ice into water, and each solid has its own melting point. Keep heating a liquid and it boils, turning into a gas, like water becoming steam.
Cooling Changes StateExplain freezing and condensing as changes caused by cooling.Cooling changes matter the other way. Freezing turns a liquid into a solid, like water into ice. Condensing turns a gas back into a liquid, like steam becoming droplets on a cold window. Melting, freezing, boiling, and condensing are the four state changes.
Changing State Goes Both WaysUnderstand that changes of state are reversible and trace water through all of them.Changing state is reversible: melting can be undone by freezing, and boiling by condensing. It is always the same substance. Water shows every change, moving between ice, liquid, and steam as we heat and cool it, again and again.

Questions this course answers

What happens when ice melts?

Melting is when heat turns a solid, like ice, into a liquid, like water.

The temperature where a solid turns into a liquid is called its...

The melting point is the temperature at which a solid turns into a liquid, like ice at 0 degrees Celsius.

When water gets hot enough to turn into steam, this is called...

Boiling is when a liquid gets hot enough to turn into a gas, like water turning into steam.

What does freezing do to liquid water?

Freezing is when a liquid gets cold enough to turn into a solid, like water becoming ice.

Steam touching a cold window turns into water droplets. This is called...

Condensing is when a gas cools down and turns into a liquid, like steam becoming droplets.

Which pair of changes are opposites of each other?

Melting turns solid to liquid, and freezing turns liquid back to solid, so they are opposites.

Grounded in trusted sources

BBC Bitesize
Britannica Kids
Royal Society of Chemistry
NASA Climate Kids

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