1. Changes of Matter
Physical Change- a change that alters the appearance or form of a substance but doesn’t produce a new substance.
Ex: melting a sample of gold
Chemical Change/Reaction- a change in matter that produces one or more new substances.
Ex: Gas produced from vinegar and baking soda.

2. Evidence for Chemical Reactions
Gas Production
Change in Temperature/Energy
Change in Color
Change in Properties
Formation of a Precipitate

3. Changes in Energy
Endothermic Reactions- a reaction in which energy is absorbed. Not all endothermic reactions result in a decrease in temperature.
Ex: frying an egg
Exothermic Reactions- a reaction in which energy is released.
Ex: the burning of airplane fuel

4. Chemical Formulas
A chemical formula is a combination of symbols that represents the elements present in the formula and the ratio of elements present.
Ex: MgCl2 - One atom of magnesium for every two atoms of chlorine.
Ratio is 1:2
How many total atoms are present in the following:
Pb(NO3)4 H2SO4 2HNO3

5. What Are Chemical Equations?
Using formulas and symbols instead of words to represent a chemical reaction.
Ex: CaCO  CaO CO2
Structure of an Equation
*Reactants-substances you start with
*Products-substances you end up with
*Arrow means “yields”

6. Subscripts vs. Coefficients
Subscripts – A number that indicates the ratio of elements in a compound.
Ex: H2O Ratio 2:1
Coefficients – a number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.
Ex: 3H2O Three molecules of water

7. Conservation of Mass
During a chemical reaction, matter is not created or destroyed.
Total mass of the reactants equals the total mass of the products.
Open System – matter can enter from or escape to the surroundings. Ex: burning wood in a fireplace
Closed System – matter is not allowed to enter or leave.
Ex: a chemical reaction in a sealed bag

8. Balancing Equations
To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.
Ex: 2H2O + O2  2H2O2
(4 hydrogen atoms and 4 oxygen atoms are present on both sides of the equation)

9. Try these!! _Na + Cl2  _NaCl Ca + Cl2  CaCl2 _H2O  _H2 + O2
N2 + _H2  _NH3
_Al2O3  _Al + _O2
P4 + _O2  P4O6
_Fe + _H2O  Fe3O4 + _H2

10. Controlling Chemical Reactions All reactions require a certain amount of activation energy to get them started.
Activation energy – the minimum amount of of
energy needed to start a chemical reaction.

11. Factors that Influence the Rate of Reactions
Surface Area
Temperature
Concentration – amount of substance in a given volume
Use a Catalyst – a material that increases the rate of a reaction
Use an Inhibitor – a material that decreases the rate of a reaction