The Water Cycle

The Water Cycle

Middle School

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Learning Objectives

• Describe the water cycle's main stages: evaporation, condensation, and precipitation.

• Explain the Sun's critical role in powering the water cycle.

• Identify how water changes states between solid, liquid, and gas.

• Connect the water cycle to weather and living organisms.

Key Vocabulary

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Water Cycle

The continuous process by which water moves between the Earth's surface and the air, changing states.

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Evaporation

The process where liquid water is heated, turns into a gas, and rises into the air.

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Condensation

The process where water vapor in the air cools and changes back into tiny liquid water droplets.

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Precipitation

Water released from clouds that falls back to Earth as rain, snow, sleet, or hail.

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Water Vapor

The invisible, gaseous form of water present in the atmosphere after the process of evaporation occurs.

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Atmosphere

The entire layer of gases that surrounds the planet Earth, which is commonly called the air.

The Three States of Water

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Solid (Ice)

• Water in its solid form is what we commonly call ice.

• Its molecules are packed tightly in a fixed crystal structure.

• Glaciers and ice caps are large solid water bodies on Earth.

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Liquid (Water)

• This is the most common state of water found on Earth.

• The molecules in liquid water can move and slide past each other.

• Oceans, rivers, and lakes are all examples of liquid water bodies.

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Gas (Water Vapor)

• Water as a gas is usually invisible and called water vapor.

• Its molecules are spread very far apart and move around freely.

• Steam from a hot kettle is a visible form of this state.

Multiple Choice

What is the primary characteristic of water when it is in its solid form, like ice?

• Its molecules are packed tightly in a fixed crystal structure.

• Its molecules can move and slide past each other.

• Its molecules are spread very far apart and move freely.

• It is the most common state of water on Earth.

Multiple Choice

What is the main difference between the molecules in liquid water and water vapor?

• Liquid molecules slide past each other, while vapor molecules are far apart and move freely.

• Liquid molecules are in a fixed structure, while vapor molecules slide past each other.

• Liquid molecules are usually invisible, while vapor molecules are visible as steam.

• Liquid molecules form large bodies like glaciers, while vapor molecules form oceans.

Multiple Choice

Based on the information about the states of water, what can be concluded when you see steam rising from a kettle?

• The water molecules are spread far apart and moving freely.

• The water molecules are locking into a fixed crystal structure.

• The water molecules are beginning to slide past one another in a large body.

• The water has become its most common state found on Earth.

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From Surface to Sky: Evaporation

• The Sun's heat changes liquid water into a gas called water vapor.

• This process of water turning into a gas is called evaporation.

• Evaporation happens from oceans, lakes, rivers, and even your skin as sweat.

• When ocean water evaporates, only the water rises, leaving the salt behind.

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Multiple Choice

What is the definition of evaporation?

• The process of a liquid changing into a gas.

• The process of a gas changing into a liquid.

• The process of a solid changing into a liquid.

• The process of a liquid changing into a solid.

Multiple Choice

What is the role of the Sun's heat in the process of evaporation?

• It provides the energy that causes water to change state.

• It cools the water, causing it to turn into a gas.

• It combines with water to create a new substance.

• It pushes the water vapor down toward the surface.

Multiple Choice

If a cup of ocean water is left in a sunny spot for a week, what is the most likely outcome?

• The cup will contain only salt.

• The cup will be completely empty.

• The salt will have evaporated with the water.

• The salt water will have turned into fresh water.

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From Sky to Surface: Condensation & Precipitation

Condensation

• Water vapor in the air cools down and changes back into tiny liquid water droplets.

• This process is the opposite of evaporation and is responsible for the formation of clouds.

• Clouds are not water vapor, but visible collections of these small, condensed water droplets.

Precipitation

• This occurs when the water droplets in a cloud combine, becoming too large and heavy.

• The cloud releases the water, which then falls from the sky back to Earth’s surface.

• Precipitation can fall in different forms, such as rain, snow, sleet, or even hail.

Multiple Choice

Which statement best describes the process of condensation?

• When water droplets in a cloud fall to the ground.

• When liquid water heats up and turns into a gas.

• When water vapor in the air cools and changes into liquid water droplets.

• When clouds are formed from invisible water vapor.

Multiple Choice

What is the relationship between condensation and precipitation?

• Precipitation is the opposite of condensation.

• Condensation forms clouds, which can then lead to precipitation.

• Precipitation must happen before condensation can occur.

• Condensation and precipitation are the same process.

Multiple Choice

Based on the processes described, what must happen within a cloud to cause it to release rain?

• The air gets colder, causing the water droplets to freeze instantly.

• The cloud moves over a large body of water and collects more vapor.

• The water droplets that form the cloud combine and become too heavy.

• The sun's energy causes the water droplets to evaporate from the cloud.

Water's Pathways and Future Outlook

• Precipitation may run off into rivers or soak into the ground for plants.

• Living organisms release water, which evaporates and continues the cycle.

• Rising temperatures could increase evaporation, leading to more precipitation and floods.

Multiple Choice

What happens to the water that living organisms release?

• It evaporates and continues the water cycle.

• It is absorbed directly by other organisms.

• It immediately freezes into ice.

• It causes precipitation to stop.

Multiple Choice

How does precipitation become available for different parts of the environment?

• It can run off into rivers or soak into the ground for plants.

• It always evaporates before it hits the ground.

• It is only used by animals and not by plants.

• It stops the water cycle from continuing.

Multiple Choice

What outcome can be predicted if global temperatures continue to rise?

• An increase in evaporation, leading to more precipitation and floods.

• A decrease in evaporation, leading to less water for plants.

• An increase in water released by living organisms.

• A decrease in the amount of water flowing in rivers.

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Common Misconceptions

Misconception	Correction
Clouds are made of water vapor.	Clouds are made of tiny liquid water droplets or ice crystals.
The water cycle has a starting point (like the ocean).	The water cycle is a continuous loop with no true beginning or end.
Water disappears when it evaporates.	Water changes its state from a liquid to a gas; it is not destroyed.

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Summary

• The Sun's energy drives the water cycle's main stages: evaporation, condensation, and precipitation.

• Water changes between solid, liquid, and gas, with clouds forming from tiny liquid droplets.

• When water evaporates from the oceans, the salt is left behind.

• Rising global temperatures may lead to increased evaporation and precipitation.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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