1. Chemical Reactions
Chapter 5
Lessons 2 and 3

2. Types of Chemical Reactions
Synthesis
Two or more substances combine and form
one compound.

3. Type of Chemical Reactions
Decomposition
One compound breaks down and forms two or more substances

4. Types of Chemical Reactions
Single-Replacement
One element replaces another element in a compound.

5. Types of Chemical Reactions
Double-Replacement
The negative ions in two compounds switch places, forming two new compounds.

6. Types of Chemical Reactions
Combustion
A substance combines with oxygen and releases energy.

7. Starting Chemical Reactions
Activation Energy is the minimum amount of energy needed to start a chemical reaction.

8. What can affect the rate of reaction?
Temperature: temperature can either speed up or slow down a reaction
Slow down: food spoilage
Speed up: baking a cake

9. What can affect the rate of reaction?
Concentration: the amount of substance present in a certain volume
A greater concentration means that the particles have a greater chance of running into each other

10. What can affect the rate of reaction?
Surface Area:
The greater the surface area the faster the reaction will occur.
Only the atoms or molecules in the outer layer of the reactant material can touch the other reactants and react.

11. How can you speed up a reaction?
Use a catalyst
The catalyst is not used up during the chemical reaction
Catalysts can either provide a surface for the reaction to take place or reduce the activation energy needed to start the reaction.

12. How can you speed up a reaction?
Use an enzyme
Enzymes are large protein molecules that speed up reactions needed for your cells to work.
Enzymes function by positioning the reacting molecules so that their structures fit together properly.

13. How can you slow down a reaction?
Use an inhibitor
An inhibitor makes the formation of a product take longer.
Many foods contain chemicals that slow down the rate of spoilage and increase the shelf life of the product.

15. Review
1. The minimum amount of energy required to start a reaction is called the _______.
2. Most chemical reactions _______ when temperature increases.

16. Review
3. Most chemical reactions _______ when concentration increases.
4. Apple slices can be kept from browning by brushing them with lemon juice. Infer what role lemon juice plays in this case.

17. Review
5. Chili can be made using ground meat or chunks of meat. Which would you choose, if you were in a hurry? Why?