Let's think about this. If students have a picture of all substances being made of tiny particles called molecules, the molecules must be very far apart in a gas since a gas occupies a very large volume compared to a liquid. The molecules must get closer together if you place them under pressure. Press the button on a cigarette lighter without igniting the flame. This is easier to do if you first break the safety mechanism to keep you from pressing the button accidentally.
Butane is a clear, colorless gas.
You might see some wavy lines like you see while filling you car with gasoline. You use the property that gasses can displace liquids to visualize the N 2 bubbles. Sometimes this property of gasses displacing liquids is described as gasses penetrating liquids. You can even ignite the bubbles as they reach the surface. However, N 2 and many other gasses can not be liquefied be pressure alone.