Ecosystems and environmental change
Download the visual resource that accompanies the session below.
Show the learners the WWT ‘Ecosystems and environmental change’ visual (you may wish to display it on an interactive board if you have one).
Where can you see water in the picture? (the ocean, the rain, the river). All this water never leaves our planet and its atmosphere, it simply moves around in what we call the ‘water cycle’. The water cycle is the journey of water from oceans to clouds to rain to rivers and back into the ocean. The water cycle involves the processes of evaporation, condensation, precipitation and surface run-off. Discuss each of these words in detail:
- Evaporation - When it rains, puddles form on the ground. Those puddles don’t stay there forever, the water in the puddle eventually seems to disappear. It doesn’t disappear, it evaporates. Evaporation is the process of water being warmed or heated and changing from a liquid into a gas (it’s still water, but now it’s water vapour and it’s mixed with the air). How might the water in this picture get heated? (the sun). Ask a learner to come and label the visual with the word ‘Evaporation’ on the surface of the water.
- Condensation - Condensation is when water changes from being gas (water vapour in the air) into a liquid. This happens when water cools. It is why when you breathe onto a cold window you get mist (water) on the windows. Your breath is warm and has water vapour in it. When your breath comes into contact with the cold glass in the window, the water vapour in it cools and condenses becoming tiny droplets of liquid water. In the water cycle, water vapour that is in the air turns into water droplets as the air cools down. These water droplets gather together to form clouds. Where is condensation happening in this picture? (the clouds). Ask a learner to come and label the visual with the word ‘Condensation’.
- Precipitation - This is when the water is released from the clouds and falls back to the surface of the Earth. One form of precipitation is rain. Where is the precipitation in this picture? (the rain). Ask a learner to come and label the visual with the word ‘Precipitation’. Can you think of any other forms of precipitation? (snow, hail or sleet).
- Absorption – when the precipitation reaches the ground it may be absorbed into the surface of the earth. Different surfaces and types of soil can absorb different amounts of water. During your visit to WWT knowing about absorption will help you to understand and appreciate the import role of wetlands in the water cycle – wetlands absorb a lot of water. Where might absorption occur in the picture?
- Surface run-off - When the precipitation reaches the ground, some of it will not be absorbed. This water trickles down mountain and hillsides, down streets, fields and paths, joining streams and rivers. When the water is flowing over the ground, this is called surface run-off. Can you see where the surface run off has joined a river in the picture? Ask a learner to come and label the visual with the word ‘Surface run-off’.
The water in the streams and rivers eventually flows into the oceans again and the whole water cycle repeats itself.
Play WWT ‘’. Give pairs of learners 4 pieces of card and ask them to write evaporation, condensation, precipitation and surface run-off, one term on each card. They shuffle the words and put them in a pile face down. Now one learner takes the top card and has to explain the word without saying the word written on the card. Learners should take turns and when they have reached the bottom of the pile, they should find another partner and repeat the activity.
Just do section A
Have a whole afternoon?
Extend section A by giving pairs of learners a copy of the WWT ‘Ecosystems and environmental change’ visual. Ask them to add: the four labels ‘Evaporation’, ‘Condensation’, ‘Precipitation’ and ‘Surface run-off’, a definition of each word, arrows to show water moving around the cycle.
Investigate evaporation by:
- Going outside after it has rained. Pairs of learners should take a piece of chalk, find a puddle in the school grounds and draw around it. They should then go back to it at different points during the day and see how the size of the puddle changes. The water is evaporating.
- Ask your class to run around the playground (you could suggest a game of tag or similar). Are any of you now hot and sweating? Discuss how the sweat we produce evaporates. It is the sweat evaporating that cools us down.
- Dampen a scrap of material and take it outside. Hang it somewhere in direct sunlight and go back to it at different points of the day. Is it getting dryer? The water in the fabric is being evaporated.