ACARA v9 CONTENT DESCRIPTION “identify sources of water and describe key processes in the water cycle, including movement of water through the sky, landscape and ocean; precipitation; evaporation; and condensation”
Builds on knowing that water can be a solid, a liquid or a gas, and on watching weather change from day to day. Here we follow one drop of water as it travels between the ocean, the sky and the land in a never-ending journey called the water cycle.
Water is stored all around us
Water is found in many places on Earth. The biggest store by far is the salty ocean, but there is also fresh water in rivers and lakes, water vapour floating in clouds, and water soaking through the soil and rock underground. The water cycle is the way water moves between all of these places, using energy from the sun.
Where is water found?
Tap each part of the land and sky to highlight a place where water is stored.
Water is stored in many places. Most of it sits in the salty ocean, but there is also fresh water in rivers and lakes, water vapour high in the clouds, and water soaking the soil and rock underground. The water cycle moves water between all of these places.
Evaporation: water rises into the sky
When the sun shines on the ocean, rivers and lakes, it heats the water. Some of the water turns into a gas called water vapour and rises up into the air. This change from liquid into vapour is called evaporation. The stronger the sunshine, the more water evaporates. You cannot see the vapour, because it is a gas, but it is carrying water up into the sky.
Evaporation: the sun lifts water into the sky
Add heat from the sun, step by step. Watch water leave the surface as invisible vapour.
When the sun heats water in the ocean, rivers and lakes, some of it turns into water vapour and rises into the sky. This is called evaporation. The more heat the sun gives, the more water evaporates. The vapour is a gas, so you cannot see it as it rises.
Condensation: vapour turns back into water
High in the sky the air is much colder. As the rising vapour cools, it changes back into tiny droplets of liquid water. This change is called condensation. Millions of these tiny droplets floating together are what we see as a cloud. The same thing happens on a cold window, where breath or steam leaves little drops of water.
Condensation: cooling makes a cloud
Switch the air high up between warm and cool, and watch a cloud appear.
High in the sky the air is much colder. When rising water vapour cools, it turns back into tiny droplets of liquid water. This is called condensation, and the millions of tiny droplets together are what we see as a cloud.
Precipitation: water falls to the ground
Inside a cloud the tiny droplets bump into each other and join up. As they grow bigger and heavier they can no longer float, so they fall to the ground. Falling water is called precipitation. When the air is mild it falls as rain, and when the air is very cold it falls as snow or hail. This is how the water that went up into the sky comes back down to the land and sea.
Precipitation: the cloud lets the water fall
Fill the cloud with droplets, then choose how cold the air is to see rain or snow.
Inside a cloud the tiny droplets join together and grow heavier. When they are too heavy to float, they fall to the ground. This falling water is called precipitation. It falls as rain when the air is mild, and as snow when the air is very cold.
Round and round: the whole cycle
Once rain reaches the land, it soaks into the ground or runs into streams and rivers. Rivers carry the water back to the ocean, where the sun can evaporate it again. So the water keeps moving in a loop: ocean to vapour, vapour to cloud, cloud to rain, rain to river, and river back to the ocean. The water cycle has no real beginning and no end.
The whole water cycle, round and round
Step through the cycle from the ocean to the sky and back. It keeps going forever.
The water cycle has no start and no end. Water evaporates from the ocean, condenses into clouds, falls as rain, and runs through rivers back to the ocean, ready to begin again. The same water has been travelling this loop for a very long time.
Why this matters
The water cycle gives us the fresh water we drink, grow food with and use every day, even though most of Earth water is salty ocean. It also explains the weather, from clear skies to rain and snow. Understanding how water moves through the sky, the landscape and the ocean helps you make sense of rivers, droughts, floods and the clouds you see overhead.
Quick self-check
1. Which of these is the largest store of water on Earth?
2. What does the sun do to water in the ocean during evaporation?
3. Why does a cloud form high up in the sky?
4. When a cloud is full and the droplets grow heavy, what happens?