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Earth & Space - Changing materials - Mixing & Separating - P5G12
This is the Teacher's Guide for this targetThis is the Teacher's Guide for this targetTeacher's Guide



1. Evaporation should have been studied in P4 but some revision may be needed. Molecules in a liquid can escape into the air a few at a time and become vapour but they need extra energy to do so. The liquid appears to vanish and we say it has evaporated but the molecules have simply dispersed into the surrounding air. If there is a cold surface nearby then those molecules colliding with it will lose their energy and return to liquid form - we call this condensation.

Moving air and heat can both speed up the evaporation process by giving more energy to the surface molecules of the liquid and allowing more of them to leave.

When investigating this allow the children to try out their own ideas but maintaining a fair test. Make sure they predict what they think will happen and write down their ideas. The investigation format given on the next page may prove useful.

In this case allow the children to suggest things which might affect the speed of evaporation. Imagine they suggest three things -

1. heat
2. blowing air across
3. putting the water in a different size dish.

Now choose one thing to investigate for example No. 2 blowing air.

This means that numbers 1 and 3 must be things which do not change throughout the investigation i.e. all the samples being compared must be kept in similar temperatures and containers.

They will probably suggest more than three things but by using lists or post-it notes they can clearly see which feature they are changing and which ones must stay the same.

Worksheet D9a (G) can be used to plan the investigation.


A good way to help the children plan an investigation is to use a modified version of the ‘Renfrewshire Investigations Package’ idea.

List on the board all the things the children can think of to investigate about the subject you have given.

Help them choose one for the whole class or one per group depending on your intended organisation.

It helps for them write out in their Science jotters sentences such

a) The things we could investigate are...  (List all their ideas here)

b) We are going to investigate...  (Write down their chosen idea)

c) To make a fair test we must keep these things the same...  (List all the things from (a) which are not being investigated.)

d) We predict that...  (What do they think they will happen)

Alternatively, write their ideas onto post-it notes.

The ideas can be listed under question (a), those not being used can then be moved to make a list under (c). This helps to clarify exactly the conditions under which the children must then plan their investigation .

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