What must happen for a chemical reaction to occur?
Particles must collide with sufficient energy and the correct orientation.
Define activation energy (Ea).
the minimum energy required for a reaction to occur when particles collide
Why do most collisions not lead to a reaction?
Many particles dont have enough energy to overcome to Ea.
Collisions in incorrect orientation
factors affecting rate of reaction
Temperature
Concentration
Surface area
Pressure
Catalyst
What does the Maxwell–Boltzmann distribution show?
The spread of molecular energies in a gas at a given temperature.
Describe the shape of a Maxwell–Boltzmann distribution curve.
Starts at the origin.
Rises to a peak (most probable energy).
Tails off to the right but never touches the x-axis.
Area under the curve = total number of particles.
What happens to curve when temp increases
peak lowers and to the right
more particles have energy >=Ea
area under curve stays the same
what happens to curve when temp decreases
peak becomes higher
moves to the left
fewer particles have energy >=Ea
How does a catalyst affect the Maxwell–Boltzmann distribution?
The shape stays the same, but the activation energy (Ea) line moves to the left, meaning more particles have enough energy to react.
What is meant by the rate of reaction?
The change in concentration of a reactant or product per unit time.
How does increasing temperature affect the rate of reaction?
Particles have more kinetic energy.
A greater proportion of particles have energy ≥ activation energy (Ea).
Collisions occur more frequently and more successfully.
Therefore, the rate of reaction increases.
Use the Maxwell–Boltzmann distribution to explain why a small temperature increase causes a large increase in rate.
curve shifts to right
and flattens
large increase in particles with energy >=Ea
small rise in temp causes more effective collisions
How does increasing concentration affect the rate of reaction?
There are more particles per unit volume.
Collisions occur more frequently.
Therefore, more successful collisions per second, increasing the rate
How does increasing the pressure of a gas affect the rate of reaction?
Gas particles are closer together.
Collision frequency increases.
More effective collisions occur per unit time, so the rate increases.
Define a catalyst.
A substance that increases the rate of a chemical reaction without being used up or chemically changed.
what does a catalyst do
provides an alternative pathway by lowering activation energy
Use the Maxwell–Boltzmann distribution to explain how a catalyst increases rate
The curve’s shape stays the same.
The Ea line moves to the left, so more particles have energy ≥ Ea.
This increases the frequency of successful collisions.
Give one industrial advantage of using catalysts.
Catalysts allow reactions to occur at lower temperatures, saving energy and reducing costs.
