If you live in a location that has snow, a good project would be to test if snow or rain is more acidic in the area. The acidity of both samples can be tested using pH strips. The child can research the causes of acid rain, and what factors would cause the result of the test. The child can then construct a poster board with the findings.
Have a child research bridge construction and also what causes earthquakes. Have the child predict what type of bridge would withstand an earthquake the best. Then he can construct model bridges and test his hypothesis by simulating an earthquake. The child could also research what causes earthquakes and what parts of the world are most prone to earthquakes.
Before modern meteorology, most of our weather prediction involved observing the clouds. A student can study the different types of weather and the associated clouds. The child can then hypothesize as to what weather conditions will occur when certain clouds are present. He can then make weather predictions on each day for a set period of time and record both the predictions and the actual results.
Children can use solar panels to power a small, electrical object, such as a light bulb or a toy car. They can also talk about the differences between renewable and nonrenewable energy sources. A student can discuss the negative repercussions that are caused by energy production in the U.S. and also ways to conserve energy.