1. Chemical Equations What happens during a chemical reaction?
There are different kinds of evidence that chemical reactions are occuring.

2. Where does the new substance come from?
In ordinary chemical reactions, atoms are rearranged through the breaking and reforming of chemical bonds.

3. Where does the new substance come from?
In the methane reaction, the bonds between carbon and hydrogen in methane are broken.
Carbon reforms a bond with the oxygen to form carbon dioxide, one of the reactants.
Hydrogen also forms a bond with additional oxygen atoms to produce water. In addition, heat and light are produced.

4. How are chemical reactions written?
Chemical reactions as sentences
Methane gas reacts with oxygen gas to produce carbon dioxide and water.
Chemical formulas are more convenient
CH4 + O CO2 + H2O
(when we use chemical formulas and symbols to represent a reaction instead of using words, it is called a chemical equation)

5. Conservation of mass
the number of each type of atom on the reactants side of a chemical equation must be equal to the number of each type of atom on the products side of the equation.
In other words, you get out of a reaction what you put into it, nothing more, nothing less.

6. What do coefficients and subscripts mean?

7. 1st Thing to remember when balancing chemical equations.
Make sure you have written the correct chemical formula for each reactant and product.
2nd Thing to remember when balancing chemical equations.
The subscripts in the chemical formulas of the reactants and products cannot be changed during the process of balancing the equation.
Changing the subscripts will change the chemical makeup of the compounds.
3rd Thing to remember when balancing chemical equations.
Numbers called coefficients are placed in front of the formulas to make the number of atoms on each side of the equation equal.
Coefficients are the only numbers which can be changed

8. Steps For Balancing an Equation

9. 1. List all of the types of atoms present in the equationC O Cl Ca

10. 2. Count the number of each type of atom on both sides

11. 3. Add coefficients to balance the equation

12. 4. Recount how many of each type of atom on each side to see if balanced. If not repeat steps 3 and 4.