Sublimation occurs when a solid changes directly to a gas.
Sublimation occurs when a solid changes directly to a gas.

It is easy to get excited about science fair projects when the experiment seems more like play than work. What lively fifth-grader doesn't love dry ice vapor cascading across the table and soap that grows into a gigantic puff? Fifth-graders are just beginning the scientific process of completing a controlled experiment, collecting data and using research to explain their findings, so it is best to keep the projects simple and engaging. These two experiments can be done in one day, have results that are impossible to miss, and demonstrate scientific processes that are familiar to fifth-graders -- sublimation and the expansion due to heat.

Effect of Temperature on the Sublimation of Dry Ice

Fill the bowl with cold water. Measure temperature.

Add a piece of dry ice, big enough to fit in a tablespoon.

Take a photo, and write observations every 15 seconds until the dry ice is gone -- sublimated into gaseous carbon dioxide.

Empty the bowl and repeat steps 1 through 3, using warm and then hot water. Capture the difference in the speed of the sublimation and the amount of vapor formed by taking photos and recording observations in your research notebook.

How Soap Reacts in the Microwave

Ivory soap floats because of air bubbles inside.
Ivory soap floats because of air bubbles inside.

Gather background information: In addition to the written research you will do on the topic before you begin your experiment, you can also do a pre-experiment demonstration, showing that Ivory soap floats while other brands do not. Place a bar of Ivory soap and two other brands of soap into a large bowl of water. Take a photo and record observations in your research notebook.

Place one bar of Ivory soap on a paper plate or microwave safe plate and place in microwave.

Microwave for two minutes, stopping every 30 seconds to open microwave and take a quick photo before restarting the microwave.

Impress the judges: Research how a microwave works.
Impress the judges: Research how a microwave works.

Repeat steps 1 and 2, using two other brands of soap.