I am in the 7th grade and I have to create a science project that is an invention and that people would want to buy. I am lost for ideas. Any help would be appreciated.

There is some science to do if you make a better mouse trap, and many people buy mouse traps. It is not the product that is important, it is figuring out how to make it better in some way, which may mean less expensive. You might provide exactly the same kind of mouse trap as your competitors, but use science to improved the manufacturing process; thereby, making a less expensive mouse trap. In this age, making a thing greener is one kind of improvement, which may mean making the factory greener, rather than directly changing the product.

I'd recommend making a few lists. What sort of mechanical/computational problems am I having in my daily life? What could I make to help my friends or family? What could I make to help the environment? What do I use now that could be made better?

 

Once you have your lists you can start brainstorming possible solutions. Feel free to use this site as a sounding board. Decent breadth of knowledge at your disposal.

Inventors spend their whole life searching for that, rarely finding - and this should be a school project?