For this demonstration of Boyle's Law, you'll need miniature marshmallows and syringes with the needles removed. Have students place three marshmallows into the syringe and press the plunger down as far as it will go without crushing the marshmallows. Next, instruct them to place their finger over one end of the syringe and pull the plunger back to the end. Inside the syringe, the volume of air increases, the pressure decreases and the marshmallows expand. Ask the students to put their finger over the end of the syringe and push the plunger in. As the pressure increases, the air volume decreases causing the marshmallows to shrink.
You can easily teach children about Boyle's Law with a simple balloon. Let students blow up a balloon and squeeze it until it pops. Explain that by squeezing the balloon they are increasing pressure and reducing the volume of the gas. The balloon bursts because it cannot withstand the added pressure.
For this demonstration of Boyle's law, you'll need a clear pot, water and a heat source, such as a burner. Put the pot of water on the burner and turn the heat to high. Have the students observe the bubbles as they form at the bottom of the pot. Point out the size of the bubbles and how they grow larger when they rise through the water. Explain that the pressure on the bubbles decreases as they move up which allows the bubbles to expand.
Here's a fun, interactive way to show younger students Boyle's Law. You'll need a hammer, nail, clear jaw with metal lid, straw, modeling clay, large marshmallows and a mirror. Make a straw-size hole in the middle of the lid using the hammer and nail. Put the straw through the hole and using the modeling clay, create an air-tight seal around the straw. Draw a face on the flat sides of one marshmallow and drop it into the jaw, screwing the lid on tightly. Place the mirror so students can see the marshmallow and suck the air out of the jaw. Because the marshmallow has air pockets, when you decrease the air pressure in the jar by sucking out the air, the marshmallow decreases in size. When you release the pressure, the air returns to the jar and the marshmallow returns to its normal size.