Technically, air is a gas. It is a mixture of nitrogen and oxygen with traces of many other gasses.
Nitrogen, N2, (about 79% in air) is a rather inert gas.
20
Approx 0.00001%
Gas will stay in a cup. If the gas is denser then air, it will settle into the cup and stay there in much the same way that a liquid will. If the gas is close to the same density as the air, or lighter, it will float away and mix with the air.
Alot
Not much. Both compress gas: the one "air", t'other some freon-based gas.
About 15 parts per million (0,0015%)
It means you have too much air intake It means you have too much air intake
It means you have too much air intake It means you have too much air intake
The drawbacks are:natural gas does burn quickly and fastnatural gas doesn't five much electricitynatural gas pollutes the air
You can only get gas heating and air conditioning. The gas heating and air conditioning is less because it uses less gas then how much water you would be using. The electricity for the heater and AC can be fairly cheep.
Chlorine is about 2.7 times denser than air.