light a match
You go to Alberta and find Steve, and Steve will help you prove it exists... Hes super cool
Water exists in our environment as a liquid gas and solid.
Aliens.
Prove that god exists
yes
Merlin is a character out of a story and there is no evidence or sightings to prove he exists
Include evidence to support you claim.
No. Any person trained in logic will tell you that 'you cannot prove a negative'. If you want to disprove the existence of fairies you first attempt to try and prove their existence. And the best you can do is to fail to prove it. The option to prove it always exists.
Water vapor is the atmospheric gas that exists in variable amounts. Its concentration can vary depending on factors such as temperature and location.
All matter exists as either a solid, liquid, gas or plasma. This is called it's 'State Of Matter'. Oxygen exists as a gas.
I don't think there is. Science can only prove what can be observed.
Carbon Dioxide. You can prove it by collecting some of the gas in a test tube (the gas is heavier than air). Drop a lighted splint into the test tube, and the flame will be extinguished.