Gas and oil are "fossil fuels" because they were created from the bodies of plants and animals that were trapped between layers of sediments, or dirt and sand that layered over them. As more and more layers of sediment were piled over them, the pressure converted their remains into oil and gas. Because it takes a very long time to make oil and gas in this way, scientists call them non-renewable resources.
How Oil is Formed
To help your child understand how oil forms, you will need some gummy candies or jellybeans and three kinds of bread, cracker or cookie crumbs. Explain that oil forms most often under an ocean. Ask your child to place a layer of crumbs on the bottom of a baking tray. Let him have some fun arranging the gummy candies on the "ocean floor" to represent creatures that float to the bottom of the ocean. Next, have him cover the creatures with a layer of differently colored crumbs. Explain that the process goes on for decades and ask him to add a different kind of crumb on top of that. Finally, apply pressure to the layers by stacking several books on top of the layers. Leave for a couple of days. Remove the books and examine what has happened to the layers. The squeezed gummy creatures represent the oil.
Explain to your child that over time, the packed earth around the oil deposits gets so hard that it turns into rock. Fill a clear glass with ice cubes, and then pour your child's favorite cold drink over the cubes. The ice cubes represent the rocks around the oil; the drink represents the oil itself. Let your child drink the fluid. Discuss how the ice cubes shift as the liquid disappears. Explain that oil is our favorite kind of fuel for making electricity, moving cars around or even heating homes. Discuss what happens when oil no longer exists between rocks and brainstorm what the world might be like without it.
Explain that it takes so long to make fossil fuels that we would have to wait millions of years for a new supply of oil. Brainstorm ways to make oil last longer, such as walking when traveling a short distance or carpooling. Make a chart of the ways that you use fossil fuels in your home. These can range from electricity from a local power plant to the spray lubricant you use to keep the chain on your child's bicycle lubricated and operating correctly. Discuss which things use the most oil and which use the least.
Discuss some of the other ways to make fuel, such as from squeezing vegetable matter or fermenting husks or stalks to make alcohol. Use a garlic press to squeeze various types of vegetables, such as garlic, onions, olives or kernels of corn to see how much liquid you can extract from each. Mix together two cups of water, one package or tablespoon of dry yeast, two tablespoons of sugar and a 1/2 cup of flour. Place the mixture in a quart jar. Stretch a balloon over the top of the jar and see what happens as the yeast grows.