Grade 4 (age 9-10)

The Water Cycle

Earth's water never disappears; it circles between sky and land. The Sun warms the sea, water rises as vapor, then cools up high and forms clouds. Rain or snow falls, runs down rivers, and returns to the sea, repeating endlessly. Watch the moving diagram to follow water from sea to clouds to rivers.

Water Goes Round and Round

💧 Water's Journey

①Sun heats the sea, water becomes vapor (evaporation)

②Vapor rises and cools to form clouds (condensation)

③Rain or snow falls from the clouds (precipitation)

④Rainwater flows down rivers back to the sea

Three States of Water

🧊 Water's Transformations

①Solid (ice): water freezes when cold (below 0°C)

②Liquid (water): the usual state

③Gas (vapor): water evaporates when hot (100°C)

④Water changes state with temperature

Summary

The Water Cycle

Sea → Evaporate → Cloud → Rain/Snow → River → Sea

Water continually cycles around Earth

Water State Changes

Ice (solid) ↔ Water (liquid) ↔ Vapor (gas)

Water changes state with temperature

🎯 Key Points

①Cycle: evaporation→condensation→precipitation→runoff→evaporation

②Solar energy drives the cycle

③Water exists as solid, liquid, and gas

④Earth's water is recycled, never newly made

⑤The cycle brings rain and flowing rivers

Examples and Unit Test

Example 1

What do we call the process where seawater warmed by the Sun turns into water vapor and rises into the sky?

When the Sun warms the sea, the water turns into water vapor and rises into the air.

This change of water into water vapor is called evaporation.

▸ Evaporation

The water cycle goes evaporation → condensation (clouds) → rain/snow → rivers → sea.

Example 2

What is the process where water vapor that rose into the sky cools and gathers into tiny droplets to form clouds?

As water vapor rises high into the sky, its temperature drops.

The cooled vapor turns into tiny water droplets that gather into clouds; this is called condensation.

▸ Condensation

Vapor cooling into droplets is condensation, the start of clouds and rain.

Unit-test style

Which statement about the water cycle is correct?

①Evaporation is water vapor turning into water

②Water changes state as it cycles

③The water on Earth is created anew more and more as it cycles

④The water cycle does not need energy from the Sun

⑤A cloud is a solid formed by water freezing

▸ ② Water changes state as it cycles

Water cycles through evaporation, condensation, and precipitation, changing between gas and liquid states.

Evaporation is water turning into vapor (①), the water on Earth is not newly made but recycled (③), the cycle is driven by energy from the Sun (④), and a cloud is gathered tiny droplets (⑤).

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