how does a gas exert pressure on a surface?

Answer 1

Lets look at gas in a balloon. Lets pretend we can see the gas molecules buzzing around on a micro-scale. At the boundary of the gas and the surface there are always some of these molecules hitting the surface. The molecules hitting the surface, much like you pushing on a surface, creates the pressure. So, the faster the molecules are traveling (due to a rise in temperature) the harder they will impact the surface. Also if there are more molecules present, more will be hitting the surface and also increase the pressure. This can be verified by analyzing the ideal gas law, PV=nRT. Where P=Pressure, n=amount of gas molecules, and T=temperature. We can see if we raise the n or T the pressure must rise also, assuming a constant V(volume).

On a macro-scale, such as our atmosphere, the gas has a mass just like anything else. Although the mass is small, there are miles of gas so the total mass has a noticeable affect here at the ground. We don't notice the pressure because we are used to it (sometimes you may notice it when your ears 'pop' driving up or down a large hill) but the atmosphere is exerting pressure on everything.

Answer 2

Molecules in a gas are constantly and randomly moving around. Each molecule has a mass, a velocity, and consequently, a momentum (p). When they bounce off of a surface, they give some of their momentum to the surface. This takes place over a finite time (t). A change in momentum over a finite time gives rise to a force. Newton's 2nd law says:

F = (change in p) / (change in t)

Now, pressure is force per unit area:

P = F / A = (change in p) / ((change in t) * A)

Its easiest to think of the molecules as little billiard balls. If you threw a bunch of billiard balls at the wall, they would exert a force on the wall. This force, divided by the area covered by the billiard balls, is the pressure they exert on the wall.

Answer 3

If you throw a ball against a wall it exerts a pressure at the moment of contact before bouncing back. In a gas the millions of molecules are doing the same thing - except that they never stop.

Answer 4

Because it has mass and when gravity acts on it it weighs something. It's just like a weight acting over a surface.

The atmosphere, which is a gas, is 200 miles thick and it presses down on the earth and everything on it, including us, with a weight that is known as atmospheric pressure which is about 15 pounds per square inch. That's why if we go beyond the atmosphere, where there is no gas and therefore no weight we don't feel the pressure and we experience ...weightlessness

Answer 5

ENTROPY CAUSES RANDOM DISORDERED MOVEMENT OF GASEOUS MOLECULES