Year 9 science project ideas please

[Violinmum1]

DD, Year 9, has been asked to make a science model for school, to submit as part of a competition. We're not in the UK, so I can go out and get things to make it with, but it has to be something that can be displayed and demonstrated over Zoom. Also nothing that would need outdoor space as we live in a flat.

It can be entered under the Physics, Chemistry or Biology categories. She has a week to complete it. Any ideas would be welcome!

Some good ones here. I like the DIY Air Conditioner
www.real-world-physics-problems.com/science-fair-project-ideas.html

You could probably demonstrate the action of lungs fairly well with hydraulics/ syringes / balloons. Quite topical?!

@FortunesFave, thanks for the link. I'll go through that.

@BridgetDrones, thanks, that would have been perfect for the current times, but they had each made an inflating model of lungs and diaphragm a couple of years ago.