Gas Laws

Gases:

  • Fill the container their in

  • Are highly compressible

  • Will naturally diffuse and mix together

  • Are made of particles that move rapidly (are always in consistent motion)

Temperature

  • A measure of average kinetic energy of particles in a substance

  • Higher temperature = faster moving particles (vise versa)

  • Determines average kinetic energy

Pressure

  • For per unit area

  • High frequency of collisions = higher pressure

  • High energy = higher pressure 

Volume

  • A volume a single gas occupies is negligible compared to the volume the particle travels (atom vs container)

  • Volume determined by size of container 

STP- is standard temperature volume and pressure SATP is standard temperature volume and pressure at room temperature (25°C)

Factors that affect pressure!

  • Gas: (a proportional relationship) increase in number of moles, particles, and collisions creates an increase in pressure

  • A decrease in number of molecules, particles, and collisions within the sides decreases the pressure

  • Volume: (inversely proportional) increase in volume, more room for molecules to move, and fewer collisions lead to decrease in pressure

  • Decrease in volume, meaning less room to move, and more collisions, is equal to an increase in pressure

  • Temperature: (Proportional relationship)

  • Increase in temp, kinetic energy, and force & frequency of collisions creates an increase in pressure (because particles are colliding with each other more often)

  • Decrease in temperature kinetic energy of particles, and force & frequency of collisions with a container wall results in a decrease of pressure (because particles are colliding with each other less often)

Kinetic energy

  • Higher kinetic energy means particles move faster!

  • Gases move in random straight line motions because they have no forces (so far apart that the forces are so low) the particles will only change direction when involved in a collision. They have perfect elastic collisions, so there is no energy transfer. Ek will stay the same

  • Collisions do not affect the temp of the colliding particles

Ideal gases

  • Obey all gas laws, do not condense into a liquid when cooled, are composed of particles w/ 0 volume and attraction 

  • Assumed to have no IMFs  between molecules since IMFs slow down molecules and reduce number of collisions

  • Gases cannot condense into a liquid if there are no IMFs they do not have any attractive forces and therefore they cannot pull molecules towards themselves 

  • Lowering temp will just lower the Ek (speed of particles)

Real gases

  • Do not obey all gas laws

  • Condense into a liquid when cooled

  • Are composed of particles w/ volume and attraction 

  • P-T and V-T charts are NOT linear 

  • Occur at high pressures and low temperatures (because molecules will get closer together and will begin attracting each other) - lower temp = lower Ek = slower moving molecules, high pressure = molecules are close together (IMFs strengthen as distances decrease)

Boyles Law

  • Between pressure and volume (inversely proportional)

Charles Law

  • Between volume and temperature (proportional)

Gay-Lussac’s Law

  • Relationships between temperature and pressure (proportional)

Ideal Gas Law

  • Used to describe relationships between pressure, temp, volume and chemical amount in a  single equation (no change = ideal gas law)