These four activities are designed to introduce students to ways in which alternative sources of energy can be used. They align with the following National Science Education Standards: Content Standard A: Science as Inquiry; and Content Standard B: Physical Science—Properties of Objects and Materials; Motions and Forces; and Transfer of Energy.
It's A Gas
Showing how the decay of organic materials can produce biogas (methane) takes a few simple ingredients: an empty 1-L plastic bottle and a standard party balloon. This activity is best performed as a demonstration that can be prepared in advance.
Caution: Students should not touch materials in this demonstration because of bacterial growth.
1. Using rubber gloves, put about 10 g of raw ground beef and 2 lettuce leaves torn into small pieces into the plastic bottle. Wash your hands thoroughly with soap and water.
2. Pour about 2 tablespoons of sand into the bottle so that it covers the meat and lettuce. Do not shake the bottle.
3. Slowly pour about 2 teaspoons of water into the bottle, making sure that the water runs down the side of the bottle and not directly onto the sand.
4. Stretch the neck of the balloon over the mouth of the bottle. Tie tightly with string and then place masking tape over the string.
5. Place the bottle in a warm location where your students can observe the balloon and the material in the bottle for the next three days.
What happened to the material at the bottom of the bottle over the three-day period? (The material began to decay.) What happened to the balloon? (It inflated.) What substance inflated the balloon? (Gas that formed during the decomposition.)
Note: When the demonstration is over, puncture the balloon in a well-ventilated place and put everything in a large plastic bag for immediate disposal.