1. Rates of Reactions
Lesson 11
September 13th, 2010

2. Rates of reactions (P260-264)
Review of Particle Theory
All Matter is made up of extremely tiny particles
Each Pure substance has its own kind of particles, different from the particles of other pure substances
Particles are always moving. Particles at a higher temperature are generally moving faster, on average than particles at a lower temperature.
Particles attract each other

3. Collision Model (theory)
Atoms and molecules are constantly bumping into each other. If they are moving too slowly or are stable, no reaction will occur. Molecules that are moving quickly enough may break bonds between atoms and the atoms may combine to form new molecules (new products).
The exact energy required for a particular old bond to be broken and a new one to be formed is called the 'Activation Energy. This is the threshold energy at or beyond which, if the collisions occur, new bonds form.

4. Collision Model (theory)
Two factors increase the rate of reaction
Number of collisions
Number effective/successful collisions

5. 4 Factors that affect rates of reactions
Temperature When the reactants are heated, they bounce and contact more vigorously with other reactant molecules. This increases the number of successful collision and the rate of reaction. This is the most important factor.

6. 4 Factors that affect rates of reactions
Concentration
Concentration is defined as the number of molecules of reactants per unit volume. The more the concentration of reactant molecules, the higher the probability of collision due to their sheer number. Excess concentration may have no effect if one of the reactants is used up.

7. 4 Factors that affect rates of reactions
Surface Area
By increasing surface area, the number of molecules exposed for collisions is increased. This allows more collisions between molecules to occur and increases the rate of reaction.

8. 4 Factors that affect rates of reactions
Catalyst
Catalysts, are chemicals or substances that catalyze or promote a chemical reaction to occur and remaining unchanged in the end. They are like parts of an assembling mechanism that help making the final product but then detach themselves from it. They lower the activation energy.

9. Homework / MSIP Complete balancing worksheet
hand in
Complete types of reactions worksheet
Complete Lab
Hand in
Read pages (today’s work)
Questions page 264 #1-5- Homework check