I've been doing a lot of science with my son, but he is older. Since he is trying to get his activity badges for cub scouts in artist and scientist, I've been combining them wherever I can.

I would suggest extracting DNA from strawberries, but I had trouble with that one with a classroom full of 4th graders, so….

What about painting with acids and bases? Great way to teach fundamentals of chemistry, and you get cool paintings too smile

http://www.kidsplaybox.com/art-activities-for-kids-red-cabbage-art/

Here's a twist on the old vinegar and baking soda eruption experiment: http://www.learnplayimagine.com/2014/02/erupting-watercolor-absorption-art.html

Another one we'd done is spin art- it teaches Newton's First Law of Motion
http://casamarias.blogspot.com.au/2012/03/spin-art-in-motionpart-one.html

You can get some really cheap salad spinners from IKEA for $3 each…