Science fair projects for third-graders can center on one of the three main science disciplines: biology, chemistry or physics. As students carry out and practice their projects, make sure that they comply with all of the health and safety regulations of the science laboratory or guidelines for safe fieldwork.

Biology

Introduce your third-grade students to biology by getting them to see how environmental factors affect the speed of a snail. Get your students to first set up a narrow snail run that is between 4 and 6 inches long and 1 inch wide using cardboard strips. Students should angle the walls of their snail run inward so that the two pieces almost touch at the top, which will make sure snails stay on course. Have students time the snail's progress from one end of the run to the other. Students should then repeat this experiment on a layer of sand and a layer of dirt to see how the surface affects snail speed.

Chemistry

An idea for an easy chemistry project for your third-graders involves seeing how different liquids evaporate. Have students place four identical bowls next to one another on a sunlit windowsill and fill each with 100 ml of the following: water, vinegar, rubbing alcohol and salty water (1 tablespoon of salt dissolved into 100 ml of water). Get students to take a marker and note the level of the liquid. Students should check back every two hours to see how much each liquid has evaporated. Have students leave their bowl for 24 hours before measuring and comparing how much liquid is left in each bowl.

Physics

A quick and simple physics project that will engage your third-grade students gets them to see how many times they can fold a piece of paper in half. Provide students with several different sizes of construction paper and get them to start folding it in half as many times as they can. Each time they make a fold, have students mark a tally in a notebook; make sure students clearly label the tallies so they know which size paper they are recording the results of. Explain exponential growth and exponential decline to your third-graders.

Health and Safety

Regardless of how easy a science project may be, you should ensure your third-grade students to wear the correct safety clothing when completing experiments. Introduce the topic of safety to your students by compiling flashcards which get them to work out what they should do next. For example, show the class a flashcard of a student about to step on broken glass, such as a beaker. Ask students to raise their hands and indicate both what will happen next and the appropriate course of action for cleaning up the broken glass.