Answer:
As you increase the temperature of a gas, its particles get more kinetic energy and move faster.
How does kinetic energy relate to temperature?
I’ll assume you know what KE is.
Consider a sample of confined gas, liquid, or solid material that’s not going anywhere. We may know it’s mass but since it’s not going anywhere, we conclude the sample has zero velocity and KE is zero.
Long ago it was noticed that a sample like this actually had parts and that they were moving. Each part of the sample had a part of the mass and all those random velocities had a combined Internal KE.
More KE in a particle also carried more momentum. So collisions involved more impulse … to each other and to what ever they touched. This causes more pressure to gas samples, more volume in most liquids and solids.
Put your skin on the surface and your nervous system responds to that impact too. We build devices that survive more extremes than our bodies and report more consistent results. We keep the ones that tend to agree with each others’ response and find those that have use in extreme conditions.
Watching a thermometer reading is a measure of its temperature. The laws of motion predict that the average KE of the device will become the same as its surroundings. An outdoor thermometer may be used to gauge the air temperature; but that is inaccurate when it is also gaining KE by being in sunlight or losing by rain evaporation or snow.