1. Science 9 Unit B: Matter and Chemical Change
Lesson 2-4: Types of Reactions (we saw yesterday) and Factors affecting rates of reaction

2. Reaction Rate a measure of how fast a reaction occurs
can be measured by how quickly a reactant disappears or product appears

3. Changing Reaction Rate
can be sped up or slowed down by:
changing the temperature
stirring the reactants
changing the size (surface area) of reactants (example: grinding a reactant into a powder
increase the concentration of a reactant (this increases the number of particles per unit volume)

4. Catalyst
a substance that speeds up the rate of reaction without being changed itself
does not affect the amount of product
increases only the speed of the reaction

5. Enzymes are natural catalysts made by living things.
almost all chemical reactions in the human body are catalyzed by enzymes
when chewing carbohydrates, salivary amylase (which is an enzyme) breaks down starches into smaller molecules
one of the most important group of enzymes are the proteases, which break down proteins
proteases are used in meat tenderizers and contact lens cleaning solutions
Video

6. Inhibitor a substance that slows down chemical reactions
inhibitors are found naturally in seeds to prevent germination until conditions are just right
an inhibitor is added to hydrogen peroxide to prevent its molecules from decomposing too quickly

7. Corrosion
is the oxidation of metals or rocks in the presence of air (oxygen) and moisture
Rust (iron oxide) is an example of corrosion 4Fe(s) + 3O2(g)  2Fe2O3(s)
(iron) (oxygen) (iron oxide)
corroded materials lose their strength
corrosion occurs on the metal surfaces and at points of strain, eventually making it all the way through

8. corrosion can be prevented:
applying a thin coat of paint
galvanization, the process of coating metals with a thin layer of zinc (example – galvanized nails)
coating car bumpers with a thin layer of chromium to protect the iron from corroding
aluminum oxidize quickly forming aluminum oxide which seals the surface and stops corroding
as a result, aluminum cans will take over 400 years to degrade

9. Electroplating
the process of covering a metal with another metal by using electrolysis is called electroplating

11. Combustion
combustion (requires heat, oxygen and fuel) is a highly exothermic combination of a substance with oxygen

12. Combustion
examples include a fireplace, a gas barbecue, or the furnace in your home
also takes place inside the internal combustion engine of a car
gasoline combines with oxygen to release energy to make the car move

13. Products of Combustion
food you eat is converted to energy by combining with the oxygen that you breathe
the combustion reaction of acetylene and oxygen is hot enough to melt metal
2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O + energy
(acetylene) + (oxygen)  (carbon dioxide) + (water vapour) + (heat)
(Acetylene torch welding)

14. Fire Triangle

15. Today: You’ll be investigation factors that affect rates of reaction
Complete Lab 2-3: Investigating Conditions that affect rate of reaction.