Kinetic Theory
Matter is made of particles, and these particles are moving.
- We can use Brownian motion and diffusion as evidence for this.
Brownian Motion - The random motion of particles suspended in a medium (either in a liquid or gas)
As the temperature increases, these particles move faster.
Temperature - A measure of the average kinetic energy of particles.
All these ideas underpins collision theory, which allows us to predict the rate of reaction.
Gases have a lot of different particles that make it up, and therefore some move relatively faster than others. As we increase the temperature of the gas, the overall “average” kinetic energy will increase, yet some particles would be moving faster and slower than this average kinetic energy. This phenomenon can be observed using the Maxwell Boltzmann Distribution.
Both the blue line and the green line are the same gas, but they are at two different temperatures. The blue line is at a lower temperature. The average kinetic energy is lower than at a higher kinetic energy. As the temperature decreases, we can see the peak of the curve increasing, meaning that more particles are at the average kinetic energy. The more temperature that is added, the “flatter” the curve and the larger the distribution.
Ideal Gases
Ideal Gases have the following properties:
- Infinitesimal Particles
- Straight Line Motion
- No force of attraction/repulsion between particles
- Elastic collisions between particles-particles and particles-walls
- Manifests pressure in a container
Pressure, Volume, and Temperature
Pressure is inversely proportional to Volume. P ∝ 1/V
- This means as pressure increases, volume decreases.
Pressure is directly proportional to Temperature. P ∝ T
- This means as pressure increases, temperature increases.
Temperature is directly proportional to Volume. T ∝ V
- This means as temperature increases, volume increases.
(Pressure is also directly proportional to the number of moles)
We can combine all these proportionalities so that we can have one equation:
\[P = \frac{nRt}{V}\]Where:
- P is pressure
- n is the number of moles
- R is the ideal gas constant = 8.314…
- t is the temperature
- V is the volume