Gases contribute to atmospheric pressure through the weight of the air molecules and their collisions with surfaces. Here’s a clear breakdown:
- Air is made of gas molecules: The atmosphere contains gases like nitrogen, oxygen, carbon dioxide, and small amounts of others. These molecules are in constant motion.
- Molecules exert force when they collide: Gas molecules move randomly and collide with each other and with surfaces (like the ground, walls, or your skin). Each collision exerts a tiny force.
- Pressure is the cumulative effect of many collisions: Atmospheric pressure is the total force per unit area from billions of gas molecule collisions happening every second.
- Weight of the air above: The air higher up in the atmosphere also presses down due to gravity. This weight contributes to the pressure felt at lower altitudes.
- Dependence on density and temperature: More molecules in a given volume (higher density) or faster-moving molecules (higher temperature) increase the pressure.
In short: Gas molecules create atmospheric pressure by colliding with surfaces and by the weight of the air above, pressing down on everything below.