Behavior of gases Physical Science

Earth’s atmosphere The atmosphere is the layers of air surrounding the Earth. The atmosphere extends from Earth’s surface to about 10,000 km above. The layers of the atmosphere (from closest to Earth’s surface to farthest) are: Troposphere Stratosphere-Where the Ozone layer is! Mesosphere Thermosphere Exosphere

Gases in the atmosphere The atmosphere is composed of many different gases. Nitrogen makes up about 78% of the Earth’s atmosphere. Oxygen makes up about 21% of the atmosphere. The remaining 1% is composed of argon, carbon dioxide, hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon.

BOYLE’S LAW AND CHARLES’ LAW-GIZMO Boyle’s law and Charles’ law describe how temperature and pressure affect a gas. Unlike a liquid, a gas’s volume will change in response to temperature and/or pressure variations.

BACKGROUND INFO Gases are composed of a sea of colliding molecules. The temperature of the gas is a measure of the average velocity of the molecules. As the molecules speed up, the temperature increases. As the molecules slow down, the temperature decreases.

PRESSURE If a gas is held in a container, it will expand to fill the entire container. As the molecules of the gas collide with the walls of the container, the gas exerts pressure on the container. Pressure is a measure of force exerted on a unit of area. The SI unit of pressure is the pascal (Pa), where 1 Pa = 1 newton per square meter (1 N/m2).

The Ideal gas law PV = nRT The ideal gas law quantifies the relationship between the volume, pressure, and temperature of a gas: PV = nRT P stands for pressure V for volume n for the number of gas molecules R for the ideal gas constant T for temperature. The gas constant R is 8.314 when p is measured in pascals, V in cubic meters, n in moles, and T in kelvins.

Boyle’s law Boyle’s law at a constant temperature, the volume of a fixed amount of gas varies inversely with pressure on the gas. As pressure increases, the volume of the gas decreases. As pressure decreases, the volume of the gas increases.

Charles’ law Charles’ law – with pressure on the gas held constant, the volume of a gas varies directly with temperature. As temperature increases, the volume of the gas increases. As temperature decreases, the volume of the gas decreases.

Absolute zero – the coldest possible temperature. The Kelvin scale measures temperature from absolute zero, so 0 K is absolute zero and 273.15 K is 0 °C. Absolute zero is equivalent to -273.15 °C, or -459.67 °F. At absolute zero, the molecules in a substance do not move.