Collision Theory and Reaction Rates 2016.notebook

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Collision TheoryAim:  To identify the conditions necessary for a chemical reaction to occur.

Review Book Topic 8Text book Chapter 17

Unit 11: Kinetics and Equilibrium

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Collision Theory

Collisions between particles do not always result in a chemical reaction.

A reaction will only occur if there is an effective collision between molecules.

To have an effective collision:1) The reactant particles MUST hit with sufficient energy2)  The reactant particles MUST have proper orientation. (Think lock and key model for enzymes)

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Collision Theory and Reaction Rates 2016.notebook

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Reaction Rate

Aim:  What factors affect the rate of a chemical reaction?

Collision Theory and Reaction Rates 2016.notebook

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What is kinetics?

Kinetics deals with the speed of chemical reactions.

Reaction Rate: the amount of time it takes for a chemical reaction to occur

Reaction rate is increased by an increase in the amount of effective collisions.

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1) Nature of the Reactants2) Concentration3) Surface Area4) Temperature5) Pressure (only affects gases)

What factors play a role in the speed of a reaction?

6) Addition of a Catalyst

Collision Theory and Reaction Rates 2016.notebook

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Nature of the Reactants

Certain substances are more reactive than others based on their chemical properties.

Example: Lithium is more reactive than Gold.

The more bonds that need to be broken the slower the reaction rate will be.

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Concentration

Increasing the concentration of the reactants will result in more collisions because there are more particles.

More collisions= a faster reaction rate (shorter time)

Collision Theory and Reaction Rates 2016.notebook

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Surface Area

Increasing the surface area of a reactant increases the number of sites where a collision can take place

Greater surface area = more collisions= faster reaction rate (shorter time)

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Temperature

Increasing temperature causes an increase in the average kinetic energy of molecules.

Higher kinetic energy means the particles move faster

This results in more collisions and a faster reaction rate.

Collision Theory and Reaction Rates 2016.notebook

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Pressure 

A change in pressure only affects gases!

Increase pressure by decreasing the volume.

Less space between particles results in more collisions.

More collisions gives a faster reaction rate.

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Collision Theory and Reaction Rates 2016.notebook

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Catalyst

Catalyst: a substance that speeds up a reaction but IS NOT A PART of the reaction.

The catalyst lowers the activation energy. (Less energy needed for an effective collision)

(Ex- Lighter fluid to light charcoals on a barbecue.)

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In short....

Increasing temperature = ________________________

Increasing concentration = ________________________

Increasing pressure = ____________________________

Increasing surface area = _________________________

Addition of a catalyst = __________________________