How to use experiments to prove that the size of atmospheric pressure is related to air density and temperature?

How to use experiments to prove that the size of atmospheric pressure is related to air density and temperature?

Use a syringe for an injection; block the head
The relationship between atmospheric pressure and air density: when the piston is pressed down, the internal gas density increases and the pressure also increases due to the decrease of gas volume;
The relationship between atmospheric pressure and temperature: move the piston to the middle of the needle tube, block the head of the needle, and heat it. At this time, you will find that the piston moves outward, indicating that the internal gas pressure increases, and the piston is pressed outward