How the heart works.
Some ideas for a third grade science project are showing how aerobic and anaerobic decomposition occurs or if food items are fruits or vegetables. Other ideas are showing how a compass works or how to tell time using the sun.
There are many science ideas to be found online. Sites such as Science Buddies, Kidz World, Cool Science Projects, and even Brown University feature dozens of science fair ideas for multiple abilities and grade levels.
A clay volcano
eating your butt
bread
There are lots of ideas for a 4th grade science project. One example is studying the solar system, learning about each planet that orbits Earth and the sun.
can plant better grow
Egg flotation, exploding volcancoes.
Look in the back of each chapter of the science book. They often have suggestions.
For a middle school aged child, you can find some excellent science fair solar system projects online. A great site to look for ideas is sciencebuddies.org. Look under the "Project Ideas" tab on that website.
Science fairs are very common in fifth grade. Some of the most common include a potato/copper battery, volcano, hydroponic experiments and a mouse-in-a-maze experiment.
You can say: does the mass of an object affect how far you throw it