1. Chemical Reactions

2. Homework
Read pages: 61-63
Worksheet: Word Equations and Reactions 2

3. Describing Chemical Change
In a chemical reaction, one or more substances (reactants) change into one or more different substances (products). Reactants Products
Chemical reactions involve chemical changes.

4. Describing chemical change
Reactants change into products
Bonds are broken
Atoms re-arrange
New bonds are formed
Atoms themselves are neither created nor destroyed!

5. Describing Chemical Change
What happens when you combine baking soda and vinegar ?
describe some of the changes.
In aqueous solution, acetic acid reacts with sodium bicarbonate to produce sodium acetate, carbon dioxide and water.

6. Describing Chemical Change
sodium bicarbonate +
aqueous
acetic acid
sodium acetate +
carbon dioxide
water

7. Separates two or more reactants or products 
Symbol
Explanation +
Separates two or more reactants or products 
Yields - separates reactants from products
→;←;↔
Reversible reaction
(s); (l); (g)
solid, liquid or gas
(aq)
Aqueous solution – a substance dissolved in water
Heat supplied
Platinum used as a catalyst
heat → Pt →

8. Chemical Equations C12H24(s) + O2(g) CO2(g) + H2O(g)
The physical state of the substances can be indicated by placing a symbol in parenthesis after the formula
C12H24(s) + O2(g) CO2(g) + H2O(g)
(s) For solid, (l) for liquid, (g) for gas, and (aq) for an aqueous solution.
Heat

9. Chemical Equations SO2(g)
What would the skeleton equation be for the following:
Sulfur burns in oxygen to produce sulfur dioxide.
S(s) + O2(g)
SO2(g)
Heat

10. Chemical Equations H2(g) + KOH(aq)
What would the skeleton equation be for the following:
When solid potassium is added to water, hydrogen gas and aqueous potassium hydroxide are produced
K(s) + H2O(l)
H2(g) + KOH(aq)

11. Homework
Read 61-63
Reactions 8 and Balancing Chemical Equations

12. Balancing Chemical Equations
Rules for Balancing Equations
Determine the correct formula of all reactants and products
Write reactant on the left and products on the right side of the arrow.
Count the total number of atoms of each element on each side.

13. Balancing Chemical Equations
Rules for Balancing Equations
Balance the elements one at a time by using coefficients – DO NOT CHANGE SUBSCRIPTS
Check each atom or polyatomic ion to make sure the equation is balanced
Make sure all coefficients are the lowest possible ratio that balances
Let’s see how it is done…

14. Balancing Chemical Equations
Balance the following equations:
SO2 + O SO3
Fe2O3 + H Fe + H2O
P + O P4O10
Al + N AlN

15. Balancing Chemical Equations
Balance the following equations:
2SO2 + O SO3
Fe2O3 + 3H Fe H2O
4P + 5O P4O10
2Al + N AlN
More Practice…