🔬 ScienceLevel 1Lesson 20
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Water Changing States

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Learning Objectives

  • 1Sequence the five steps of water changing from solid ice to steam
  • 2Name the four change processes — melting, freezing, evaporation, and condensation
  • 3Explain that heat drives these changes
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Mini Lesson

Water is remarkable — it is the only substance on Earth that we regularly experience in all three states of matter. The same water molecules become ice in your freezer, liquid in your glass, and invisible steam above a boiling kettle.

Adding heat: solid to liquid to gas

  1. Step 1 — Ice (solid): Water is frozen into a fixed shape. Temperature is at or below 32°F (0°C).
  2. Step 2 — Melting begins: Heat is added. The ice warms up and starts to lose its rigid shape at the edges.
  3. Step 3 — Liquid water: All the ice has melted. Water flows freely and takes the shape of its container.
  4. Step 4 — Heating to boiling: More heat is added. The water gets hotter and hotter until it reaches 212°F (100°C).
  5. Step 5 — Steam (gas): Water boils and turns into steam — invisible water vapor that rises into the air.

Names for the changes

Condensation in everyday life

  • The droplets on the outside of a cold glass on a hot day — that is condensation. Water vapor from the warm air is cooling on the cold glass surface.
  • Clouds form when water vapor in warm air rises, cools, and condenses into tiny droplets.
The three states of waterThree tiles side by side — an ice cube labeled solid, a glass of water labeled liquid, and a kettle with rising steam labeled gas. Arrows show the direction of heat being added.Three States of WaterIcesolidbelow 0°C+heatWaterliquidflows freely+heatSteamgas100°C+ vaporAdd heat → solid · liquid · gasRemove heat → gas · liquid · solid
The same water molecules — ice, water, and steam.
The water cycleA loop showing the water cycle — the sun heats a lake, water evaporates up to a cloud, the cloud releases rain, and the rain falls back to the lake. Arrows show the direction of the cycle.The Water CycleCLOUDLAKEevaporation(liquid → gas)rain(condense)sun heats water → vapor rises → cools → falls as rain
Evaporation and condensation — water travels in a never-ending loop.
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Ask yourself: "Is heat being added or removed? Adding heat moves water toward gas. Removing heat moves it toward solid."

Vocabulary
Melting
Solid changes to liquid when heat is addede.g. Ice melts into water
Freezing
Liquid changes to solid when heat is removede.g. Water freezes into ice
Evaporation
Liquid changes to gas when heat is addede.g. Water evaporates into steam or vapor
Condensation
Gas changes to liquid when heat is removede.g. Steam condenses into water droplets on a cold surface
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