Grade 4 (age 9-10)

States of Water

Water changes form with temperature: solid ice, liquid water, or vapor. Cold molecules quiver in place, while warmer ones move freely and dash about fast. Drying laundry is slow evaporation, a boiling kettle bubbles, and drops on a cold cup are condensation. Drag the slider to watch the molecules move.

Water has three forms

Temperature25°C

💧 Three States of Water

①Ice (solid): molecules vibrate in place

②Water (liquid): molecules move freely

③Vapor (gas): molecules fly fast in all directions

④Higher temperature → faster motion

Evaporation vs. Boiling

🔥 Evaporation vs. Boiling

①Evaporation: slow vaporization from surface (any temp)

②Boiling: active vaporization inside (at 100°C)

③Drying laundry = evaporation

④Bubbling kettle = boiling

What is Condensation?

🪟 Vapor Back to Water

①Hot vapor on a cold glass forms droplets

②This is condensation (gas → liquid)

③Clouds, fog, dew all form by condensation

④Vapor turns to liquid in cold places

Summary

Water State Changes

Ice (0°C) ↔ Water ↔ Vapor (100°C)

Temperature drives solid ↔ liquid ↔ gas changes

Names of Changes

Melt (S→L) / Boil (L→G) / Condense (G→L) / Freeze (L→S)

Each transition has a name

🎯 Key Points

①Water has 3 states: solid, liquid, gas

②0°C: ice↔water, 100°C: water↔vapor

③Evaporation slow from surface; boiling active inside

④Condensation: vapor → droplets in cold

⑤State changes — water itself is the same substance

Examples and Unit Test

Example 1

What process is laundry drying, and what process is water bubbling in a kettle?

Evaporation happens slowly only at the surface of water, and at any temperature.

Boiling is vigorous vaporization that happens even inside the water at 100°C, so drying laundry is evaporation and the kettle is boiling.

▸ Drying laundry = evaporation / kettle = boiling

Evaporation happens slowly at the surface; boiling happens vigorously inside too.

Example 2

Why do water droplets form on the outside of a cold drink cup?

Water vapor (a gas) in the air cools when it touches the cold surface of the cup.

The cooled vapor turns into tiny water droplets (a liquid); this is called condensation.

▸ Because water vapor in the air condenses (gas → liquid)

Condensation is water vapor turning into droplets on a cold surface.

Unit-test style

Which statement about the changes of state of water is correct?

①Boiling happens only at the surface of water

②Condensation is water vapor turning into water

③Evaporation happens only at 100°C

④When water freezes it turns into a different substance

⑤Water vapor is water in a solid state

▸ ② Condensation is water vapor turning into water

Condensation is when water vapor, a gas, cools and turns into liquid water droplets.

Boiling happens vigorously inside the water too (①), evaporation happens at the surface at any temperature (③), water stays the same substance when it freezes (④), and water vapor is water in a gas state (⑤).

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