invisible gas
Put a tablespoon of baking soda into a wide mouth jar. Put
about 3 ounces [about 1/3 cup] of vinegar into the jar. You
can use lemon or grapefruit juice instead of vinegar. The jar
fills with the invisible gas carbon dioxide. It is heavier
than air. That makes the gas sink in air instead of rising
and floating away. It stays in the jar just as water would.
To prove the gas is there have a small lighted candle nearby.
If you are under 15 years old get an adult's permission when
doing anything with fire. Fire can kill and destroy in ways
that you may not know about. When the baking soda and vinegar
has stopped bubbling lift the jar and move it over to the
candle. Tilt the jar as you would to pour water from it.
But do not tilt it so much that any of the vinegar solution
pours out. Tip the jar quickly to get a large amount of gas
down over the flame all at once. The candle will go out.
Carbon dioxide can be poured because it is heavier than air.
That makes the gas sink in air when you tip the jar.
The flame goes out because the carbon dioxide pushes the air
away from the flame. Without air the flame cannot burn.
We cannot see the carbon dioxide gas. We cannot smell it or
taste it. Yet we know it is there. We can do something with
it that produces a result.
Another version of this is to place a short candle inside a
container whose sides are higher than the top of the candle's
flame. Then pour the gas into the container.