Pressure Section 16.3

The Atmosphere Gases in the atmosphere-oxygen, argon, carbon dioxide, nitrogen, hydrogen, water vapor, some other elements Gravity holds particles in. Particles have mass

Earth’s Atmosphere Troposphere- from 0 to 10 km- the layer that we live in every day Stratosphere- from 10 to 50 km-contains the ozone layer Mesosphere- from 50 to 85 km- the coldest layer Thermosphere- from km-auroras form here Exosphere- beyond 500 km- very hot- region where the Hubble Space Telescope orbits

Pressure Pressure = F/A Units: F = newtons (N) A = m 2 P = kPa Air causes expansion because: air particles collide with the walls of their container, forcing the walls outward More air added to container without flexible walls = more pressure Pressure of gas- # of times the particles strike the walls of the container

Pressure When containers expand- pressure decreases because particles don’t collide with walls of the container more often Boyle’s Law-If volume decreases, pressure of the gas will increase Helium balloon-as it rises, pressure decreases, allowing the volume to expand until the balloon ruptures

Pressure, Volume, and Temperature Boyle’s Law-P 1 V 1 = P 2 V 2 Temperature & amount of gas must be constant Aerosol cans-when heated, gas hits walls more often, pressure increases, can explodes Charles’s Law-volume of a gas increases with increasing temperature provided the pressure does not change Reason-hotter = particles move faster = hit walls more often, forcing walls outward

Charles’s Law V 1 /T 1 =V 2 /T 2