Collision Theory

Define Collision Theory

• chemical reactions occur only if reactant atoms/molecules/ions collide

• They must do this with correct orientation, and enough kinetic energy, E_k, to not only break bonds, but form new ones (the products) as well

What is Kinetic Energy? What is it proportional to?

1. movement of particles

2. proportional to temp in K

Average K.E is proportional to?

temp in K

Define Activation Energy

• denoted by E_A

• minimum amount of energy colliding molecules must have for reaction to happen

• helps overcome repulsion and weaken reactant bonds

How do reactions get to a transition state? What is formed as a result?

1. when enough energy reaches the activation energy

2. products!

What factors affect the Rate of Reactions? How do they affect the rate?

1. Temperature

2. Concentration

3. Particle Size

4. Pressure

5. Catalyst

they increase the # of successful collisions

What is Temperature? How does it affect the rate of a reaction?

• average kinetic energy of particles

• Increased temp. = increased kinetic energy = more energy for collisions = increased rate of collisions

• small increases in temp. have big effects of rate (double rate for every 10°C)

What does a Maxwell-Boltzmann graph look like?

What is Concentration? How does it affect the rate of a reaction?

increased con._products = increased # of collisions = increased rate of reaction

Which picture would have an increased rate of reaction? Why?

the right picture because it has a higher concentration of reactants

Which picture would have an increased rate of reaction? Why?

the right picture because it has a smaller particles for reactants

What is Particle Size? How does it affect the rate of a reaction?

Also known as Surface Area

• decreasing particle size increases rate of reaction for heterogenous mixtures

• Larger particles splitting into smaller parts increases surface area = increased contact = increased # of collisions

What can be the cause of industrial accidents?

• Larger particles splitting into smaller parts increases surface area

Which picture would have an increased rate of reaction? Why?

the picture on the right since with a higher pressure, the particles are closer together and are more likely to collide

What is Pressure? How does it affect the rate of a reaction?

• For GASES, increasing pressure increases rate of reaction

• higher pressure compresses the gas increasing its concentration

What are Catalysts and how do they affect the rate of reactions?

1. entities that increase rate of reaction by using alternative route

2. are not used up in reaction

Example of Maxwell-Boltzmann Diagram

What are some real life examples of catalysts?

Catalytic Converters	Enzymes	Green Chemistry
device that converts toxic gas → less harmful ones	biological catalysts	Catalysis seeks to reduce negative impact of chemical processes on environment