Changing states

Understanding melting, freezing, evaporation and condensation, and the water cycle

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Try each question. If you're stuck, leave it and come back. The answer key is on the last page.

1
Put the stages of the water cycle in the correct order, starting with evaporation. Put these in order: Evaporation (water turns to vapour), Condensation (vapour forms clouds), Precipitation (rain or snow falls), Collection (water gathers in rivers and seas)
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2
What is it called when a solid turns into a liquid? A) Melting B) Freezing C) Evaporation D) Condensation
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3
Complete the sentence about freezing. Water freezes at ___ degrees Celsius.
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4
What happens when ice is heated above 0 degrees Celsius? A) It melts into water B) It freezes C) It evaporates D) It stays the same
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5
What is evaporation? A) A liquid turning into a gas at its surface B) A gas turning into a liquid C) A solid turning into a liquid D) A liquid turning into a solid
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6
True or false? Evaporation only happens when water boils at 100 degrees Celsius. A) True B) False
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7
Order these processes from the one that needs the most heat to the one that releases heat. Put these in order: Evaporation, Melting, Condensation, Freezing
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8
Wet washing dries faster on a hot, windy day than on a cold, still day. Why? A) Heat gives water particles more energy to evaporate, and wind carries the vapour away B) The wind blows the water onto the ground C) Hot days have more gravity D) Cold days have more water in the air
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9
True or false? Condensation and evaporation are reversible changes - no new substances are made. A) True B) False
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10
Why does a glass of cold water get droplets on the outside on a warm day? A) Water vapour in the warm air condenses on the cold glass surface B) The water leaks through the glass C) The cold water pushes droplets through the glass D) The glass is sweating
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Answer key

Changing states · for parents and teachers

1
Evaporation (water turns to vapour), Condensation (vapour forms clouds), Precipitation (rain or snow falls), Collection (water gathers in rivers and seas)
The water cycle: water evaporates from seas and lakes, rises and condenses into clouds, falls as precipitation (rain/snow), then collects in rivers and seas before the cycle repeats.
2
Melting
Melting is when a solid gains heat energy and its particles move faster until they break free of their fixed positions and become a liquid.
3
0
Water freezes (turns from liquid to solid) at 0 degrees Celsius. This is also called the freezing point of water.
4
It melts into water
When ice is heated above 0 degrees Celsius it melts, changing from a solid to a liquid.
5
A liquid turning into a gas at its surface
Evaporation is when liquid particles at the surface gain enough energy to escape as gas. It happens at any temperature, not just at boiling point.
6
False
False. Evaporation happens at any temperature. Particles at the surface of a liquid can escape as gas whenever they have enough energy. Boiling is rapid evaporation throughout the liquid at 100 degrees Celsius.
7
Evaporation, Melting, Condensation, Freezing
Evaporation needs the most heat (liquid to gas). Melting needs heat (solid to liquid). Condensation releases heat (gas to liquid). Freezing releases heat (liquid to solid).
8
Heat gives water particles more energy to evaporate, and wind carries the vapour away
Higher temperatures give water particles more energy to escape as gas. Wind removes the vapour near the surface, allowing more particles to evaporate. Both factors speed up drying.
9
True
True. Changing state is reversible. Water can evaporate to steam and condense back to water - it is still the same substance (H2O) throughout. No new materials are created.
10
Water vapour in the warm air condenses on the cold glass surface
The warm air contains invisible water vapour. When this vapour touches the cold glass surface, it loses energy and condenses into visible liquid droplets on the outside of the glass.