Fire is a chemical reaction (combustion) involving hot gases and plasma. The three things you need for a flame are oxygen, fuel, and a spark. When the fuel (gaseous wax) and oxygen (from the air) combine in a flame, one of the gases produced is carbon dioxide.
Most people think of carbon dioxide as dry ice, and are fascinated to watch the solid chunk sublimate from solid straight to gas, skipping the liquid state altogether. You’ve seen the curls of dry ice vapor curl down and cover the floor in a thick, wispy fog. Is carbon dioxide always more dense than air, or can we get it to float?
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The answer is… yes! Here’s an experiment that will walk you through how to create a hot, invisible cloud of carbon dioxide and detect where that cloud is.
Materials:
- three candles
- adult help
- blocks or stones
- LARGE jar that fits over all three candles (watch video)
Download Student Worksheet & Exercises
Carbon dioxide changes volume when you heat or cool it. When you heat the CO2, the volume expands, lowering the density to less than that of air. When the CO2 cools, the cloud contracts (gets smaller), and the density increases as it falls to the floor.
Remember density is mass per unit volume. So it’s an inverse relationship – when volume goes up, density goes down. In this experiment, when the temperature goes up, the volume goes up, and the density goes down.
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AWESOME!!!!!!!!!!!!!!!!!!!