The Water Cycle
Grade 4 · Science · Study Guide
Follow the journey of water as it moves continuously through Earth's systems.
The water cycle is the continuous movement of water through Earth's systems. It has no beginning or end — water is always moving and changing forms. The same water that dinosaurs drank millions of years ago is still cycling through Earth today!
Evaporation is when liquid water is heated by the sun and turns into water vapor (gas). This happens from oceans, lakes, rivers, and puddles. Transpiration is when plants release water vapor through their leaves. Together, these processes move enormous amounts of water into the atmosphere.
As water vapor rises, it cools and changes back into tiny liquid droplets — this is called condensation. These droplets collect together to form clouds. When enough water collects in clouds, it falls back to Earth as precipitation — rain, snow, sleet, or hail. Water that falls on land may flow into rivers and lakes as runoff, or soak into the ground as groundwater. Then the cycle begins again!
Key terms
- Water cycle
- The continuous movement of water through Earth's systems by evaporation, condensation, and precipitation
- Evaporation
- Liquid water turning into water vapor (gas) due to heat
- Condensation
- Water vapor cooling and turning back into liquid water droplets
- Precipitation
- Water falling from clouds as rain, snow, sleet, or hail
- Transpiration
- The release of water vapor from plant leaves
- Runoff
- Water that flows over land into rivers, lakes, and oceans
Flashcards
- Evaporation
- Liquid water turns to water vapor when heated by the sun
- Condensation
- Water vapor cools and turns to liquid droplets forming clouds
- Precipitation
- Water falling from clouds as rain, snow, sleet, or hail
- Runoff
- Water flowing over land into rivers and lakes
- Transpiration
- Water vapor released through plant leaves
- Water cycle
- The continuous recycling of water through Earth's systems
Practice questions
What is it called when water vapor cools and turns into liquid droplets to form clouds?
- Evaporation
- Precipitation
- Condensation
- Runoff
Show answer
Answer: Condensation
Condensation is when water vapor cools and turns into tiny liquid droplets. These droplets collect to form clouds.
Which energy source drives the water cycle?
- Wind
- The moon
- The sun
- Ocean currents
Show answer
Answer: The sun
The sun provides heat energy that evaporates water from oceans and other bodies of water, powering the water cycle.
The water cycle has a definite beginning and end.
Show answer
Answer: False
The water cycle is a continuous cycle with no beginning or end. Water is always moving through different stages.
Precipitation can be rain, snow, sleet, or hail.
Show answer
Answer: True
Precipitation is any form of water falling from clouds. It can be liquid (rain) or solid (snow, sleet, hail) depending on temperature.
When liquid water is heated and turns into water vapor, the process is called ___.
Show answer
Answer: evaporation
Evaporation is when liquid water absorbs heat energy and changes into water vapor, rising into the atmosphere.
Fun facts
- The same water molecules on Earth today were here when dinosaurs roamed — water is constantly recycled!
- About 97% of Earth's water is in the oceans — too salty to drink.
- Plants release so much water vapor that the Amazon rainforest creates its own rainfall!
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