In this presentation you will: explore the stages of the water cycle ClassAct SRS enabled.

Firstly, it makes up 70% of living things. Water covers the majority of the surface of the earth. Water is vital to life on Earth for two main reasons. Firstly, it makes up 70% of living things. Secondly, it provides an environment for those organisms that live in water. Next >

Our Water is Millions of Years Old At one time or another, all the water molecules on the planet have been in an ocean, a river, a plant, an animal, a cloud, a raindrop or a glacier. Another interesting fact is that the water we drink today is the same water that the dinosaurs drank millions of years ago! Next >

Water Can Gain Energy Wherever water is on the surface of the earth, it can be heated by radiation from the sun. The sun provides it with energy. Condensation Evaporation Rain The water can be affected by weather conditions too. For example, water in the oceans will form large waves when a storm is near. This also gives large amounts of energy to the water. Next >

Question 1 Which process transfers heat from the sun to the oceans? A) Convection B) Radiation C) Conduction D) Correlation

Evaporation The energy that the water gains helps it to evaporate. Evaporation is the changing of a liquid to a gas. During the evaporation process, impurities in the water are left behind. As a result, the water vapor that enters the atmosphere is cleaner. Water can evaporate into the atmosphere from oceans, seas, lakes, pools, snow, and living organisms. Next >

Factors that Affect Evaporation The amount of natural evaporation that takes place is affected by the wind. The warmer and drier the wind, the higher the rate of evaporation. The main factor affecting evaporation is temperature. Water evaporates more quickly at higher temperatures. Next >

Question 2 Which of the following factors does NOT affect the rate of evaporation? A) Temperature B) Mass C) Humidity D) Wind

Convection When water evaporates, it becomes water vapor. The sun continues to supply energy so the water vapor (a gas) gets warmer. When a gas is heated it expands, its volume gets larger. This makes it less dense than the air above it, so it rises. This upwards flow is called a convection current. Next >

Question 3 Why does warm water vapor rise? A) Because it is less dense than the air above it. B) Because it is escaping from the ocean. C) Because of evaporation. D) Because it is attracted by clouds.

Condensation As the vapor rises it will also cool down. When it has cooled, it may condense. Condensation is the process by which water vapor changes from a vapor to a liquid. Water vapor condenses onto small airborne particles to form dew, fog or clouds. Next >

Question 4 Which of the following correctly describes the term 'condensation'? A) It is the changing of a liquid into a solid B) It is the changing of a gas into a liquid C) It is the changing of a solid into a gas D) It is the changing of a liquid into a gas

Rain, Snow or Hail Clouds contain water vapor and cloud droplets, which are small drops of condensed water. These droplets are much too small to fall out of the cloud, but they are large enough to make the cloud visible. If the water drops become large enough, the water will fall from clouds in the form of rain, snow or hail. This delivers the atmospheric water back to the Earth. This process is called precipitation. Next >

Rainfall Most of the rain or snow that falls lands directly back into water. Some of the rain falls onto land. It can then: evaporate again soak into the soil or rock run off the surface. Next >

Soaking into the Ground Water on the surface soaks into the ground. This depends upon the permeability of the soil or rock. Groundwater tends to move slowly. In some cases, it can take thousands of years to return as surface water. Due to the force of gravity, the water returns to the land surface at a lower point than where it entered. Next >

Percolation Percolation is the downward movement of water through soil and rock. This occurs below the root zone (the depth of soil penetrated by plant roots). Ground water percolates through the soil in the same way as water fills a sponge. It moves from space to space along fractures in rock or through sand or gravel. Next >

Question 5 What name is given to the process of water passing through rocks below the earth's surface? A) Evaporation B) Convection C) Condensation D) Percolation

Run-Off Water that does not soak into the ground or evaporate immediately will run off the land. It will form streams, which in turn form rivers that run into lakes or eventually the oceans. In this way the cycle will then be ready to repeat itself. Next >

Summary After completing this presentation you should be able to: show knowledge and understanding of the stages of the water cycle End >