1. Chemical Reactions

2. Reactants & Products
During a chemical equation, reactants (the stuff you start with) are changed into products (the stuff you finish with)
The products actually are composed of the same stuff you started with, but the molecules have been rearranged by chemical bonding to produce completely new compounds with unique physical properties
A basic chemical equation looks like this:
REACTANTS PRODUCTS

3. What you put in (before) = reactant
A chemical reaction is when atoms interact with each other to form new substances
What you put in (before) = reactant
What comes out (after) = product
Mass of reactants = mass of products
MASS IS CONSERVED

4. Conservation of Mass
A chemical equation is a chemical reaction in which reactants and products (separated by an arrow) are expressed as formulas
The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical reaction

5. Balancing Equations/Manipulating Coefficients
In order to show that mass is conserved during a reaction, a chemical equation must be balanced
A coefficient is the number that appears BEFORE a formula
Recall that subscripts are used to balance a formula
Coefficients are used to balance the equation

6. Steps to balancing a chemical equation:
1. Write out the chemical equation
2. Balance the most unusual element or compound first, use subscripts as a guide
3. Continue with other elements, ending with the most common
Example: Balance the chemical equation
C2H6 + O2 → H2O + CO2
2 C2H6 + 7 O2 → 6 H2O + 4 CO2

7. Moles & Molar Mass
a mole is the SI unit that measures the amount of substance
A mole contains 6.02 x 1023 particles (molecules, atoms, Formula units) of a substance
Molar mass is the mass of one mole
Molar mass is calculated by adding up the atomic masses of each element (multiplied by the subscript)
Example: CO2
Carbon = 12 * 1(subscript) = 12
Oxygen = 16* 2 = 32 +
The molar mass of CO2 is g

8. Types of Reactions Synthesis Decomposition Single displacement
Double displacement
Combustion reactions

9. Synthesis or Combination Reactions
synthesis reactions occur when two substances combine to form a new more complex substance
general form A + B → AB
Example: 2H2 + O2 → 2H2O

10. Decomposition
Decomposition occurs when one large substance breaks down to two or more smaller substances
general form AB → A + B
Example: 2NaClO3 → 2NaCl + 3O2

11. Single Displacement
Single displacement reactions occur when atoms of one element take the place of an element in a compound
general form XA + B → A + XB
example 3CuCl2 + 2Al → 2AlCl3 + 3Cu

12. Double Displacement
Double displacement reactions occur when two compounds exchange their elements
general form AX + BY → AY + BX
example : AgNO3 + HCl → AgCl + HNO3

13. Combustion combustion reactions occur when a compound and oxygen burn
With enough oxygen the products are carbon dioxide and water
without enough the products are carbon monoxide and water
general form A + O2 → H2O + CO2
example 2CH4 + 4O2 → 4H2O + 2CO2

14. Energy Changes & Chemical Reactions
Indications of a chemical reaction include color change, gas formation, and temperature change
Atoms are just rearranged as bonds are broken and new ones formed
Breaking bonds requires energy
Forming bonds releases energy

15. chemical energy is the energy stored in the chemical bonds of a substance
Chemical reactions involve the breaking of chemical bonds in the reactants & the formation of chemical bonds in the products
Q: Does breaking chemical bonds require energy or release energy?

16. Exothermic & Endothermic
Reactions that release energy are exothermic
Reactions that absorb energy are endothermic
ENERGY IS CONSERVED.
Example: for an exothermic reaction energy stored in bonds (chemical energy) = energy released during reaction

17. Conservation of Energy
Law of Conservation of Energy: during a chemical reaction, energy is neither created nor destroyed
In exothermic reactions, the chemical energy of the reactants is converted to heat plus the chemical energy of the products