Reaction Rate Lesson

Reaction rate

The speed at which a chemical reaction occurs.

Activation energy

The minimum energy needed for a chemical reaction to occur.

Collision theory

A reaction occurs when particles collide with enough energy and in the correct orientation.

Two requirements for a reaction

Particles must collide with enough energy and in the correct orientation.

Effect of increasing temperature

Increases reaction rate because particles move faster and collide more often.

Effect of decreasing temperature

Decreases reaction rate because particles move slower and collide less often.

Surface area

The amount of exposed area available for particles to react.

Effect of increasing surface area

Increases reaction rate because more particles are exposed and able to react.

Example of increased surface area

Crushing an Alka-Seltzer tablet makes it react faster because more surface area is exposed to water.

Effect of increasing concentration

Increases reaction rate because there are more particles available to collide.

Effect of decreasing concentration

Decreases reaction rate because there are fewer particles available to collide.

Elephant toothpaste

A rapid decomposition of hydrogen peroxide that releases oxygen gas, creating foam.

Hydrogen peroxide concentration

As hydrogen peroxide concentration increases, the reaction becomes faster, hotter, and produces more foam.

Catalyst

A substance that speeds up a chemical reaction by lowering the activation energy.

Effect of a catalyst

A catalyst lowers the activation energy required for a reaction to occur.

Does a catalyst get used up?

No. A catalyst helps a reaction occur but is not consumed by the reaction.

Factors that increase reaction rate

Higher temperature, greater surface area, higher concentration, and catalysts.

Higher temperature vs. lower temperature

Higher temperature = faster reaction; lower temperature = slower reaction.

Greater surface area vs. smaller surface area

Greater surface area = faster reaction; smaller surface area = slower reaction.

Higher concentration vs. lower concentration

Higher concentration = faster reaction; lower concentration = slower reaction.