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The Water Cycle - PowerPoint PPT Presentation

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The Water Cycle. 75% of Earth’s surface is covered with ocean. 25% of the surface is land (7 continents). Maybe that’s why Earth is called the Water Planet. The atmosphere over all Earth also contains water in the form of vapour. But there are two kinds of water:.

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The Water Cycle

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75% of Earth’s surface is covered with ocean.

25% of the surface is land (7 continents).

Maybe that’s why Earth is called the Water Planet.

The atmosphere over all Earth also contains water in the form of vapour.

But there are two kinds of water:

Salt wateris in the oceans

Fresh water

is everywhere else

Most (97%) of the water on Earth is salt water in the oceans.

Earth’s water

Only about 3% of Earth’s water is fresh water.

Salt waterin the oceans


Fresh water


There are may types of plants and animals that live in the salt water oceans.

But all the plants and animals that don’t live in the ocean must have fresh (not salt) water to live and grow.

Salt water from the oceans becomes fresh water in a process we call the…Water Cycle.

fresh water

Salt water

The water cycle begins when energy from the sun heats ocean water.

This heat energy causes evaporation.

evaporation ee va poh ray shun

evaporated; evaporating

  • from Latin evaporare, steam, vapor

  • Spanish equivalent : evaporación

  • when liquid water becomes vapour

Evaporation is what happens when water “dries up.”

Water from the oceans is constantly evaporating. Sunlight makes water evaporate faster.

When water evaporates, molecules of water become vapour and float up into the air. Only pure water can evaporate. The salt stays behind in the ocean.







Some vapour gets into the air as it is released from plants. This is called transpiration.

Water vapour is not visible in the atmosphere until it cools and condenses into clouds.

condensation con den say shun

condensed; condensing

  • from Latin condensare, to thicken

  • Spanish equivalent : condensación

  • when vapour becomes liquid water

Condensation is the next part of the water cycle where vapour cools and forms clumps of liquid water.

Warm air can hold a lot of vapour but when air cools the vapour condenses into bigger and bigger droplets.

Vapour condenses more and more as it gets cooler. Droplets get bigger and clouds get darker.

When the droplets get too heavy they fall to the ground as liquid or frozen water. This step in the water cycle is called precipitation.

precipitation pree sip ih tay shun

precipitate; precipitating

  • from Latin praecipitare, to fall

  • Spanish equivalent : precipitación

  • any water that falls from the sky

    (rain, snow, sleet, hail)

Precipitation is how the land areas get fresh water that plants and animals need to live.

Some of the precipitation falls as snow. It may lay on the ground all winter then melt slowly to keep rivers running all summer.

Some precipitation falls as snow and does not melt for many years. Most of Earth’s fresh water is stored in glaciers.

Some precipitation seeps down underground to form aquifers.We can drill wells to get this fresh water.


Some precipitation collects in lakes, and ponds. Even if water is green, we call it fresh water. Fresh doesn’t mean clean, it means not salty.

A lot of the precipitation runs off into streams and rivers where it flows back to the ocean. This is called runoff.


Precipitation that doesn’t soak into the ground and “runs off” the land to get back to the oceans.

Eventually, all fresh water gets back to the ocean where the cycle of evaporation, condensation, precipitationand runoffcan go on and on to supply fresh water to our planet.

A cycle is a wheel that is constantly turning

Earth’s water is in a constant cycle.It evaporates from the ocean, travels through the air, rains down on the landand then flows back to the ocean.

Evaporation speeds up when water is heated.

Earth’s atmosphere is warmer near the equator where the Sun’s ray are more direct. The north and south polar regions are colder.






This is why the areas around the equator where the world is hotter have more rain and humidity.



Some parts of the world seem to be very dry, but even in the desert, there is water.

Every living plant and animal contains water and there is water vapour in the air.

For millions of years, some of the rain water that falls has been soaking deep underground. You can find water in these aquifers almost anyplace you drill.

Name 3 kinds of fresh water

Vapour vay pohr

Water that is in the gas state.

Water molecules that have been evaporated.

Vapour is usually invisible but hot steam can be seen for a few seconds before it disappears.

Dew (doo)

Small droplets of water that appear on the ground in early morning. Dew can occur even with no clouds when humid air cools at night. Many small animals get the water they need from dew drops.

Convection current

Air movements caused by uneven heating of the Earth and temperature differences.

Hot air rises, colder air sinks. The result is wind.

Aquifer (ah kwih fur)

Big areas of underground water that can be found by drilling almost anyplace on Earth. This is also called the water table.

Drought (rhymes with out)

An usually dry period with less than normal amounts of rainfall.

Flood (flahd)

An usually wet period with more than normal amounts of rainfall when rivers can’t carry the runoff.


The chemical formula for water.

H2 (2 hydrogen atoms) + O (1 oxygen atom)


( 1 water molecule)

Frozen H2O = ice

Liquid H2O = water

Gas H2O = vapor

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