Target Audience
Key Stage 2 (Yr 4/5)
Link to the National Curriculum (2014)
Pupils should be taught to:
“Demonstrate that dissolving, mixing and changes of state are reversible”
Objective
- To enable children to understand that it is possible to reverse some changes to materials.
Preliminary Activities
- Re–unite the children with the story of the Gingerbread Man asking them to recall the story before reading it to them.
- Split the children into groups to make Gingerbread Men of their own (over a period of weekly cooking sessions) and in the process demonstrating that the ingredients for making the gingerbread men once used cannot be turned back to their original form.( see down loads for recipe for ginger bread men also investigation sheets for further activity)
- Pose the following problem to the children relating to the story after all groups have undertaken the activity) No-one could catch the Gingerbread man, so why did he elect to jump on the fox’s back when he could quite easily have swum across?
What you need
- Groups of Gingerbread Men of three different sizes.
- Simple equalising scale balance ( sort used in the infant department)
- Empty ice-cream containers.
- Forks
- Weights ( in this case washers or standardised plastic or metal weights)
What you do
- Watch the video clip from the website practicalprimaryscience.co.uk
- Weigh each of the gingerbread men (small medium and large) using the washers or standard weights with the equalising balance and record their weights. This could also be done with plastic or metal weights
- Now take each gingerbread man in turn and place him in the water until he sinks. Carefully take him out and reweigh him. Again record the individual weights
- When all three have been reweighed in water, compare the results and discuss the out come with the children referring to the original problem.
How it works
- The Gingerbread men absorbed water increasing their individual weights in proportion to their original sizes demonstrating that in this case the changes were reversible if they (the gingerbread men) were carefully dried out. They would return to their original weight. This change therefore could be described as a physical change only because no chemical change occurred
- This could be compared with the other non-reversible cooking chemical change when the Gingerbread men were made, as the original ingredients could not return to their original raw state.
Follow up work
- This could involve further non reversible cooking activities
- The rain cycle where water could be shown to exist in the three reversible states of ice, water, steam( water vapour)