1. CHEMICAL REACTIONS

2. DESCRIBING CHEMICAL CHANGE
In a chemical reaction (rxn), one or more substances (reactants) change into one or more different substances (products).
reactants products
Chemical rxns involve chemical changes.

3. DESCRIBING CHEMICAL CHANGE
Reactants change into products:
bonds are broken
atoms rearrange
new bonds are formed
Atoms themselves are neither created nor destroyed!

4. DESCRIBING CHEMICAL CHANGE
baking soda + vinegar → ?
In aqueous solution, acetic acid reacts with sodium bicarbonate to produce sodium acetate, carbon dioxide and water.

5. DESCRIBING CHEMICAL CHANGE
sodium
bicarbonate +
aqueous
acetic acid
sodium acetate +
carbon dioxide
water

6. → → Symbol Explanation + separates one or more reactants or products →
yields – separates reactants from products
→ ← 
reversible reaction
(s), (l), (g)
solid, liquid, gas
(aq)
aqueous soln – substance dissolved in water
heat or Δ
heat supplied Pt
platinum is a catalyst
heat → Pt →

7. CHEMICAL EQUATIONS
physical states of the substances indicated by symbol in parentheses after the formula
C12H O2 → CO H2O
(s) (g) (g) (g)

8. CHEMICAL EQUATIONS
example: sulfur burns in oxygen to produce sulfur dioxide
S(s) + O2(g) → SO2(g)
heat

9. CHEMICAL EQUATIONS
example: when solid potassium is added to water, hydrogen gas and aqueous potassium hydroxide are produced
K(s) + H2O(l) → H2(g) + KOH(aq)

10. BALANCING CHEMICAL EQUATIONS
burning candle equation:
C12H24(s) + O2(g) → CO2(g) + H2O(l)
when one molecule of wax reacts, does one molecule of CO2 form?
C12H24(s) + 18 O2(g) →
12 CO2(g) + 12 H2O(l) 18 12 12

11. BALANCING CHEMICAL EQUATIONS: RULES
Determine the correct formula for all reactants and products.
Write reactants on left and products on right of the arrow.
Count the total number of atoms of each element on each side.

12. BALANCING CHEMICAL EQUATIONS: RULES
Balance the elements one at a time using coefficients – DO NOT CHANGE SUBSCRIPTS
Check each atom or polyatomic ion to make sure the equation is balanced.

13. BALANCING CHEMICAL EQUATIONS: RULES
Make sure all coefficients are in the lowest possible ratio.

14. BALANCE THE FOLLOWING EQUATIONS:
SO O2 → SO3
Fe2O H2 → Fe H2O
P O2 → P4O10
Al N2 → AlN

15. BALANCE THE FOLLOWING EQUATIONS:
2 SO O2 → 2 SO3
Fe2O H2 → 2 Fe H2O
4 P O2 → P4O10
2 Al N2 → 2 AlN

16. WRITE AND BALANCE (USING MODELS):
Hydrogen gas + elemental oxygen yields water.

17. WRITE AND BALANCE (USING MODELS):
Solid sulfur + oxygen gas yields sulfur trioxide gas.
Nitrogen gas + hydrogen gas yields gaseous ammonia (NH3).