This place has some great science and history ideas for the third grade. These could be edited to work with a higher or lower grade. Third Grade Thinkers: Science: Earth Cycles Need to make sure its accurate to prevent misconceptions!
Summer Activity and Science: EYFS DINOSAUR TOPIC: Children can help to "hatch open" the dinosaur egg using salt and tools, revealing small dino toys. Made by simply putting toy inside balloon, fill with water, freeze overnight then cut balloon away.
Colorful Fizzy Fun: Pinner says "This kept my 2 year busy for an entire hour and my 4 year old busy for 2 hours! Drop vinegar tinted with food coloring onto a pan filled with baking soda. Sheer minutes of colorful fizzy fun!