Like many scientists who lived 300 years ago, Benjamin Franklin worked on lots of different problems in science. But it wasn’t enough for him to just understand the science. With each discovery he made an invention: something to make people’s lives easier and safer. He made no money from his inventions, believing that they should be used freely by everyone.

Make your own water cycle...

This activity demonstrates that water not only evaporates, but it also will condense as well.

You will need...

A large square tub, such as an ice cream tub
Some clingfilm
A small pebble
One handful of modelling clay
Water
Blue food colouring

How long?

This will take about half an hour to an hour to build depending on how long they want to spend making their islands. You may need to help them to put the clingfilm on.

In a sunny spot the water will start to evaporate immediately, and drops will start to appear in their lakes within an hour.

What to do...

You may want to divide the class into pairs or small groups for this activity so they can discuss what is happening in their water cycles.

The full instructions are given on the students' pages.

What's happening?

  1. Can the students point to where different processes are happening in their water cycle?
  2. Where is evaporation happening?
  3. What is evaporating?
  4. Where is the water vapour?
  5. Where is condensation happening?
  6. What is condensing?
  7. Can they find other daily examples of where they can see condensation and evaporation?

Curriculum Links

Science:

Working scientifically

 

Lower Key stage 2  Year 4
States of matter

 

Upper key stage 2 Year 5
Properties and changes of material

Literacy:

Reading - Comprehension

Geography:

Human and physical geography

 

 

 

 

Scottish Curriculum

Science:

SCN 2-05a

Planet Earth - Processes of the planet

 

SCN 2-12a

Biological systems - Body systems and cells

Investigating some body systems and potential problems which they may develop. Making informed decisions to help me to maintain my health and wellbeing

 

SCN 2-12b

Biological systems - Body systems and cells

Exploring the structure and function of sensory organs to develop my understanding of body actions in response to outside conditions.

Wet and dry

It was hot in the summer of 1750 in Philadelphia, but Benjamin Franklin wasn't as hot as everyone else.

He had discovered that wearing wet clothes on a breezy day made you cooler. Although this is something that most people know whether they are on the beach or out in the rain, Benjamin Franklin went on to study why this happened, noticing that this is the reason why people sweat.

His experiments showed that when liquid water evaporated into water vapour it took some of the heat with it. Today, scientists can cool things to astonishingly low temperatures by evaporation.

Benjamin Franklin's wet clothes dried because they took heat from his body, in the same way that clothes dry on a washing line by taking heat from the Sun. Wind speeds up drying because it blows the water vapour away.

In the water cycle, water evaporates from the sea, lakes, rivers, and even plants. This water vapour condenses into clouds, rain falls, and the rain collects to form lakes and rivers which flow to the sea.

Try making your own water cycle...

Download a pdf of the instructions here.
Modelling the water cycle



 

 

You will need...

A large square tub, such as an ice cream tub
Some clingfilm
A small pebble
One handful of modelling clay
Water
Blue food colouring

What to do...

1. Make a small island out of the modelling clay. The island needs to be much smaller than your tub. Make a hollow in the middle, which can form your inland lake. Don't make it too deep or it may never fill up enough to run down into the sea again.

2. Put your island in the middle of your tub.

3. Pour enough water around your island to cover the base, and add a few drops of blue food colouring.

4. Cover the top of the tub with clingfilm. You will need to seal the whole tub so no water vapour can escape, but don't pull the clingfilm too tight as you will want it to hang down into the tub.

5. Put the pebble on top of the clingfilm so the clingfilm is pulled down towards your island, directly above your lake.

6. Carefully lift the whole thing and put it somewhere sunny. If it is warm enough, your water cycle will start within minutes.

What is happening?

Water from around the island starts to evaporate, turning into a gas, water vapour. Some of this water vapour turns back into a liquid when it reaches the clingfilm covering the tub. You will be able to see drops of water there. This water runs down the clingfilm (because of the pebble weighing it down) and drops off onto the island as if it were raining. If you have made a lake, the lake will fill up and eventually overflow as a river which flows back down into the sea.

If you have used food colouring you will notice how the water in the lake is clear - fresh water - while water in the sea is coloured - salt water. The water cycle purifies the water.