Our science objective this week is to investigate evaporation and condensation using practical experiments. It links very closely to our work in geography now too and you can refer to last weeks geography experiment using the sea (water with salt) and river.
Firstly, recap evaporation and condensation practically. You could explore what happens to a puddle over time (create one if it has not been raining!). What do children think will happen? How can we measure what is happening? Perimeter? Diameter? Length across widest point? Could draw chalk line around puddle once an hour/half hour (when dry then take digital photo of lines). Can children explain what has happened to the water? It becomes a gas. What do they think causes the drying? (Wind, sunshine.) This process is called evaporation.
Or look at any other everyday examples? Washing drying on a line, water boiling in a saucepan, kettle boiling. Steam is composed of tiny droplets of water, which can be seen, and then which become invisible water vapour (gas). The water hasn’t ‘disappeared’ but has become a gas.
What happens when children breathe onto a mirror? What can they see/feel? Water droplets. Where has the water come from? Water vapour in the air from lungs. This process is called condensation.
Point out that these changes in the state of water (by evaporation & condensation) are reversible changes.
Now watch the clip about fair testing at http://www.bbc.co.uk/education/clips/z684d2p and then using the resource sheets conduct your pwn evaporation experiment.
How will they ensure their test is fair? This could be very tricky for some children, depending on how much testing they’ve set up before. An explanation, with examples of fair testing, and a range of possible enquiry questions are listed in the session resources if chn need a prompt or reminder. Chn should record their question, the equipment they need, how they will make their test fair and the method they will use before they start. They record their results as they carry out the enquiry and then discuss their findings before drawing a simple conclusion. A labelled diagram should be drawn. Explain the recording sheet – assess their understanding of ‘prediction’, ‘observation’ and ‘conclusion’ from the previous session.
There is also a further task on preparing a diary to record your water use at home during the next week.