There are many experiments you can perform in order to prove that gases are poor thermal conductors. You can try heating up an enclosed space from the top and feeling the bottom for example.
An experiment can prove or disprove a hypothesis.
Prove causation
Experiment
That depends on the result of the experiment. The experiment is a way to test a hypothesis, and it's completely fine if the experiment disproves the hypothesis. Ideally, though, the experiment will support the hypothesis.
Galileo
to prove it worked.
An experiment can prove they are wrong or right ...:)
Electricity is the propogation of electrons down a chain of atoms, a copper wire for instance. Gases are too spread out to pass electrons from one atom to the next, although they may be spread in to dense enough clouds for this to occur. This would explain why they are semi conductive. This is a guess but you could prove it by checking for a correlation between a gases conductivity and its density.
This was an experiment to prove universal gravitation!
An experiment can show: Cause and effect (Apex).
By experiment.
The first step is to decide on the purpose of the experiment. What is it that you are trying to prove or disprove.