4.11 Vocabulary - 10/8/07• Reaction rate: The speed at which reactants

form products. Reactions rates can be modified.

• Temperature: The average kinetic energy of particles.

• Concentration: The amount of a specified substance in a unit amount of another substance.

• Surface area: A measure of the exposed area • Catalyst: A substance added to the reactants

that increases the rate of a reaction without being consumed in the process.

• Particle collisions: an interaction between particles which causes an energy transfer.

Catalysts & Reaction Rates

PS-4.11 Explain the effects of temperature, concentration, surface area, and the presence of a catalyst on reaction rates.

Chemical Reactions• Occur when reactants collide!• Reactants must collide with sufficient

energy to react!• It is important to consider particle

collisions when looking at reactions!

What factors affect the rate of a reaction?

Reaction rate factors include:• Temperature• Concentration• Surface area• Catalysts

Temperature

When temperature increases, the rate of a chemical reaction increases.

• Higher temp More collisions!

Concentration

When reactants are concentrated, the rate of a chemical reaction will increase.

• Better odds of collision if concentrated!

Surface AreaWhen the surface area of reactants

increases, the reaction rate increases.• Better odds of collisions with smaller

particle size!

Catalysts• The presence of a catalyst will speed

up a chemical reaction by lowering the amount of energy needed to start a reaction

Catalysts• Catalysts remain unchanged in a

reaction and do not change amount of product, they only change the rate of production!

Elephant toothpaste

• Write out this formula & balance it:• Dihydrogendioxide breaks down into water & oxygen gas

• 2H2O2 2H2O + O2(g)

• What kid of equation is this?

• Decomposition

Elephant toothpaste• 2H2O2 2H2O + O2(g)

• Think about when you get a cut & use hydrogen peroxide…. It bubbles up. That bubbly gas is oxygen.

• Hydrogen Peroxide isn’t very stable, so it is constantly breaking down.

• It’s always decomposing to water and oxygen

• Under normal conditions, the decomposition goes very slowly. 

Elephant toothpaste• 2H2O2 2H2O + O2(g)

• Do you want to see it speed up????• Add yeast, it catalyzes the

decomposition, making the reaction go much more quickly. 

• Add a dish soap, the oxygen gas gets stuck in the soap making it bubbly

• Add food coloring….you get colored elephant toothpaste!

REVIEWWhat is the average kinetic energy of

particles called?TemperatureWhat is the amount of exposed area

called?Surface areaWhat is the amount of a specified

substance in a unit amount of another substance?

Concentration

REVIEWWhat is speed at which reactants turn

into products called?Reaction RateWhat is an interaction between particles

which causes an energy transfer?Particle collisionsWhat do you call a substance that you

add to the reactants that increases the rate of a reaction?

Catalyst

REVIEWTrue or False: Catalysts are consumed

by the chemical reaction.

False

What is the effect of increased temperature on a chemical reaction?

It speeds up!

What is the effect of concentration on a chemical reaction?

It speeds up!

REVIEWWhat is the effect of increased

temperature on a chemical reaction?

It speeds up!

What is the effect of a smaller surface area on a chemical reaction?

It speeds up!

Chemical reactions only occur when there is enough ___________.

Energy!