how about shower heads and see which one uses the most water or less water and tell them which shower head is the best to use or get different types of gum and see which flavor last longer

When my daughter was in second grade she did a project on how fire extinguishers worked. We did the baking soda in a kleenex “bag” tied to a string in a bottle filled with a little vinegar and a balloon on the top. Then you shake the bottle, the balloon expands, and flies off the bottle — like the pressure in the extinguisher. I found a picture of the inside of an extinguisher and llightly drew it then she colored and labeled it. We also set up an appointment with our local fire department and they were real nice. They set up a “burn” so she could learn how to put out a fire and I took lots of pictures. It was a great experience for her and she got an A on the project. When you give any assistance on a project remember — don’t do it for the child but say that Soandso helped with whatever ( drawing, labeling, etc.) Let 99% be the child’s work no matter how it looks then it’s done by the student. That’s the learning process. Good luck!