How to make a pine cone hygrometer

A hygrometer (say: high-GROM-uh-ter) is an instrument used to measure moisture in the air, also called humidity. Examine your pine cones. Take a photo or draw a picture, paying special attention to the scales.

Place your pine cones in the bowl of water and let them soak for 45 minutes. Examine your pine cones again. Take another photo or draw another picture, observing how the wet pine cone scales look different than when they were dry.

1. Preheat the oven to 200 and line the baking pan with aluminum foil.

2. Transfer the pine cones to your baking pan. Have an adult or older sibling help you place the pan in the oven and bake at 200 degrees for 30 minutes.

3. Have an adult or older sibling help you remove the pan from the oven and then carefully remove the pine cones from the pan. How do the scales look now? If you like, take one more photo or draw a final picture.

What happened:The rough ridges on pine cones are scales with seeds inside. When there's a lot of moisture in the air, the scales absorb the humidity, which causes them to swell and "close" the pine cone. This protects the seeds since too much moisture could make the seeds rot or grow mold. But when the air dries out, the moisture in the pine cone's scales evaporates, so they open up again and the seeds to fall out.