BEHAVIOR OF GASES

The amount of force exerted per unit area PRESSURE The amount of force exerted per unit area

Pressure = force / area

Unit on pressure is PASCAL (Pa) PASCAL = Newton / meter2

The atmosphere on Earth exerts pressure on everything. How much pressure? About 100,000 Pa!!! (~100kPa)

100,000N = weight of a large truck This means that in every square meter, 100,000N of pressure is exerted. 100,000N = weight of a large truck

As you move farther from the earth, the pressure becomes MUCH less. Which layer would have the least pressure? Why?

Pressure depends on how often the particles hit the surface More times = more pressure

Characteristics of Gases Negligible Volume (very compressible) Gases are in constant motion Collisions are completely elastic No forces off attraction or repulsion Kinetic energy of a gas is directly proportional to the temperature

BOYLE’S LAW For a given amount of gas at a constant temperature the volume of the gas varies inversely with pressure.

CHARLES’S LAW Volume of a gas increases if the temperature increases (pressure staying constant)

How could Charles’s Law be used to explain why hot air balloons fill up.

If temperature is constant when V decreases then P _________ INCREASES

If pressure is constant when T increases then V _________

What happens when you relax in a swimming pool? You float!!! Duh…but why?

BUOYANCY The ability of a liquid or gas to push up on an object placed in it (you in a swimming pool)

If the buoyant force is greater than the weight, then object FLOATS! If not…it sinks.

DENSITY The relationship of the mass (weight) to how much space it takes up (volume)

ARCHIMEDE’S PRINCIPLE The buoyant force on an object in a fluid is equal the weight of the fluid displaced