Aoife,
Do you have an outline for this activity? Heated Air is quite a general topic and I am not sure how it links to Sun and Shadows Toolkit.
It seems as if you might be considering making a hot air balloon, which I have seen done at second level, but not at primary.
Curious Minds has water fountain, which uses warm air to make water into a fountain. There is also PopTop.
With regards to the explicit teaching of “discussing the properties of gases and the kinetic theory of matter,” please note that the SESE Science curriculum refers to:
matter: anything that takes up space and has mass; all substances and materials can be called matter; solid, liquid and gas are the terms used to describe the three states of matter; it is possible to convert one state into another by either heating or cooling
In Junior Cycle Science students will “develop and use models to describe the atomic nature of matter … ”
When developing predictions at primary level I would not use the language of “hypothesis formulation,” but ask them to explain what they think might happen in terms of their own understanding.
You mention precise measurements and controls. What measurements would you expect them to make? A discussion about precision vs accuracy would be of interest to some of the more able children, but is generally a Leaving Cert Physics discussion. Controls in experiments tend to appear more in biology, so what would you expect the children to control? Would they keep one balloon at room temperature? Place another inflated balloon into the fridge? Place a third balloon into sunlight?