The Gas LawsThe Gas Laws

Section 3.2Section 3.2

PressurePressure

I.I. Pressure – The result of a force Pressure – The result of a force distributed over an areadistributed over an areaA. SI Unit = Pascal (Pa)A. SI Unit = Pascal (Pa)

Pa = Newton/mPa = Newton/m22

1. A Newton is a measure of 1. A Newton is a measure of forceforce

2. (Meter)2. (Meter)22 is a measure of is a measure of areaarea

3. 1000 Pa = 1 KPa3. 1000 Pa = 1 KPa

PressurePressure

B.B. The pressure in a closed container of gas is The pressure in a closed container of gas is caused by collisions between the particles of caused by collisions between the particles of a gas and the walls of the containera gas and the walls of the container1. The speed and frequency of collision have 1. The speed and frequency of collision have

a direct affect on pressurea direct affect on pressure2. As speed increases the pressure 2. As speed increases the pressure increases, as speed decreases the increases, as speed decreases the pressure decreasespressure decreases3. The mass of the particles also affects the 3. The mass of the particles also affects the

pressurepressure

Factors that Affect Gas Factors that Affect Gas PressurePressure

A.A. TemperatureTemperature1. Raising the temperature of a gas will 1. Raising the temperature of a gas will increase the pressure if the volume of the increase the pressure if the volume of the gas and number of particles are constantgas and number of particles are constant2. As the temperature rises, the average 2. As the temperature rises, the average kinetic energy of the particles in the air kinetic energy of the particles in the air increasesincreases3. With increased kinetic energy, the 3. With increased kinetic energy, the particles move faster and collide more often particles move faster and collide more often with the walls of the containerwith the walls of the container

B. VolumeB. Volume

1. Reducing the volume of a gas 1. Reducing the volume of a gas increases its pressure if the temperature increases its pressure if the temperature of the gas and the number of particles of the gas and the number of particles are constantare constant

2. As the volume is decreased, particles 2. As the volume is decreased, particles of trapped air collide more often with the of trapped air collide more often with the walls of the containerwalls of the container

C.C. Number of ParticlesNumber of Particles

1. Increasing the number of particles will 1. Increasing the number of particles will increase the pressure of a gas if the increase the pressure of a gas if the temperature and the volume are constanttemperature and the volume are constant

2. The more particles there are in the 2. The more particles there are in the same volume, the greater the number of same volume, the greater the number of collisions and the greater the pressurecollisions and the greater the pressure

Charles’s LawCharles’s Law

A.A. States that the volume of a gas is States that the volume of a gas is directly proportional to its temperature directly proportional to its temperature in Kelvin if the pressure and the number in Kelvin if the pressure and the number of particles are constantof particles are constant

B.B. Absolute zero – the temperature of 0 K Absolute zero – the temperature of 0 K or -273or -273°C°C

C.C. The formula equals The formula equals

Temperature must beTemperature must be

written in Kelvinwritten in Kelvin

D. As a gas cools to temperatures near D. As a gas cools to temperatures near 0K, the gas changes to a solid, liquid, or 0K, the gas changes to a solid, liquid, or sometimes a Bose-Einstein condensatesometimes a Bose-Einstein condensate

Charles’s LawCharles’s Law

Boyle’s LawBoyle’s Law

A.A. The volume of a gas is inversely The volume of a gas is inversely proportional to its pressure if the proportional to its pressure if the temperature and the number of temperature and the number of particles are constant.particles are constant.

B.B. The formula equals PThe formula equals P11VV11 = P = P22VV22

Boyle’s LawBoyle’s Law

The Combined Gas LawThe Combined Gas Law

A.A. Describes the relationship among the Describes the relationship among the temperature, volume, and pressure of a gas temperature, volume, and pressure of a gas when the number of particles is constantwhen the number of particles is constant

B.B. The formula equals The formula equals

C. Scientists need lawsC. Scientists need laws to deal with situations into deal with situations in which multiple variableswhich multiple variables are changingare changing

D. What will happen to the volume of a weather D. What will happen to the volume of a weather balloon as it rises through the atmosphere?balloon as it rises through the atmosphere?1. A decrease in pressure should cause the 1. A decrease in pressure should cause the balloon to expand to a larger volumeballoon to expand to a larger volume2. A decrease in temperature should cause 2. A decrease in temperature should cause the balloon to contract to a smaller volumethe balloon to contract to a smaller volume3. Whether the balloon expands or contracts 3. Whether the balloon expands or contracts depends on the size of the changes in depends on the size of the changes in pressure and temperaturepressure and temperature

Plot

Boyle’s

Law

Plot

Charles’s

Law