1. Chemical Reactions:

2. a well defined example of a chemical change.
Chemical reaction:
a well defined example of a chemical change.

3. The substances that are about to react.
Reactants:
The substances that are about to react.

4. The new substances produced.
Products:
The new substances produced.

5. Law of Conservation of Mass:
In a chemical reaction, matter is not created or destroyed but is conserved.

6. Writing equations:
A variety of symbols are used when writing equations: Chemical symbols, other symbols, subscripts, and coefficients.

7. Coefficient:
Represents the number of units of each substance taking part in a reaction.

8. Subscripts
The little numbers in a chemical equation on the right side of elements which tells you the number of element atoms are present

9. A balanced chemical equation:
Has the same number of atoms on each side of the equation.

10. Steps for balancing an equation:

11. Step 1: Write a chemical equation for the reaction.
H2(g) + O2(g) --> H2 O(l)

12. Step 2: H2(g) + O2(g) --> H2 O(l) Check equation for atom balance.
H = H = 2
O = O = 1

13. Step 3: If there is atom balance, then you are done.
If there is not atom balance, you must choose coefficients.(This is a trial & error procedure. It gets easier with practice.)

14. Choosing coefficients
2H2(g) + O2(g) -->2 H2 O(l)
H = H = 4
O = O = 2

15. This procedure will get easier as you practice!

16. Symbols in Chemical Equations Chart

17. Energy in Chemical Reactions

18. Exothermic Reactions:
Some form of energy is given off by the reaction. (heat, light)

19. Endothermic Reaction:
Some form of energy must be added for the reaction to take place. (heat, light)

20. A substance added to speed up a chemical reaction.
Catalyst:
A substance added to speed up a chemical reaction.

21. Used to prevent chemical reactions from occurring.
Inhibitors:
Used to prevent chemical reactions from occurring.