1. Chemical Reactions Table of Contents
Identifying Physical and Chemical Changes
Describing Chemical Reactions
Controlling Chemical Reactions

2. Identifying Physical and Chemical Changes
Physical Properties Chemical Properties
**In a _______________change, all substances keep their original identities.

3. Identifying Physical and Chemical Changes
Conservation of Mass
Count the atoms of each element before and after the chemical change.

4. Identifying Physical and Chemical Changes
Describe how you would plot the data from the table onto the graph. What would be a good name for the graph?

5. Describing Chemical Reactions
Chemical Formulas
The formula of a compound identifies the elements in the compound and the ratio in which their atoms or ions are present. What are the missing chemical formulas in the table?

6. Describing Chemical Reactions
Modeling a Chemical Equation
Like a skateboard, a chemical equation has a basic structure. How many complete skateboards can be made from the parts pictured?

7. Describing Chemical Reactions
Molecules of nitrogen (N2) and hydrogen (H2) react to form ammonia (NH3). How many H2 and N2 molecules are needed to yield two molecules of NH3? In a balanced chemical equation, the number of atoms is conserved.

8. Describing Chemical Reactions
Conservation of Mass
In a chemical reaction, matter is not created or destroyed. What is the mass of iron sulfide produced by this reaction?

9. Describing Chemical Reactions
The steps below show you how to balance a chemical equation.
Step 1
Write the Equation
Step 2
Count the Atoms
Step 3
Use Coefficients to Balance Atoms
Step 4
Look Back and Check

10. Describing Chemical Reactions
Hydrogen Fuel Cells

11. Controlling Chemical Reactions
A chemical reaction needs a push to the “top of the mountain” to get started. Where has enough activation energy been added to start the reaction?

12. Controlling Chemical Reactions
Graphs of Exothermic and Endothermic Reactions
Each of the graphs shows the amount of energy before and after the reaction. On each graph, determine whether energy is absorbed or released.

13. Controlling Chemical Reactions
Surface Area Temperature Concentration
Increasing temperature, __________ the rate of the chemical reaction.
Decreasing the temperature ________the rate of the chemical reaction.
Increasing the concentration, __________ the rate of the chemical reaction.
Decreasing the concentration, ________the rate of the chemical reaction.

14. Controlling Chemical Reactions
Catalysts
Adding a catalyst speeds up a chemical reaction. How would the energy graph change for the same chemical reaction if a catalyst were used?