Matter: Hot or Cold

Question 1

What is the average thermal energy of a particle?

Answer 1

kT - Boltzmann’s constant, multiplied by the temperature of the particle

Question 2

What is the symbol for activation energy?

Answer 2

ε

Question 3

Give an example of an activation energy.

Answer 3

Changing state (energy between molecules) Thermionic emission (electrons escaping the surface of the metal) Ionisation (removing an electron from an atom) Conduction in a semiconductor (electrons jumping to the conduction band) Viscous flow (Heating the particles reduced viscosity - weaker IMFs)

Question 4

At what ratio between activation energy and particle energy does a process happen at a steady rate?

Answer 4

∼30

Question 5

Why is it that when ε/kT = 30, a process is still able to occur?

Answer 5

Because a fraction of the particles have at least the activation energy - kT is the average energy per particle. Billions of particles collide each second, so even if it is a small fraction of the particles, it is still a very large number of particles with ε.

Question 6

If the number of particles with energy (kT + E) = f of the number of particles with energy kT, what is the number of particles with energy (kT + 3E)?

Answer 6

f³ times the total number of particles

Question 7

What is the Boltzmann Factor?

Answer 7

e^-ε/kTor n/n₀

Where: ε = activation energy

k = Boltzmann’s constant

T = Temperature in kelvin

n = number of particles with energy ε or greater

n₀ = total number of particles

Question 8

How does temperature affect the Boltzmann factor?

Answer 8

Increasing the temperature increases the Boltzmann factor.

Question 9

Why is the rate of reaction proportional to the Boltzmann factor?

Answer 9

Because the Boltzmann factor is proportional to temperature, and the rate of reaction is proportional to temperature. Therefore, the Boltzmann factor is proportional to rate of reaction.