How to balance chemical equations.

1. How to balance chemical equations. When pieces of matter come together or break apart, it is called a reaction. The law of conservation of matter states that matter can not be created or destroyed. In any reaction, you must have the same amount of each part before and after the reaction happens. We show how reactions become balanced by using chemical equations.

2. How to balance chemical equations. This is a balanced chemical equation. 2Na + Cl22NaCl

3. How to balance chemical equations. The arrow is called the yields sign. It separates what you start with on the left from what you end up with on the right. 2Na + Cl2 2NaCl

4. How to balance chemical equations. To the left of the yields sign are the parts that react. They are called the reactants. 2Na + Cl22NaCl

5. How to balance chemical equations. To the right of the yields sign is what you end up with after the reaction. These are called the products. 2Na + Cl22NaCl

6. How to balance chemical equations. The little number next to and below an element is called a subscript. We have been using them all along. We never change subscripts in a chemical equation. 2Na + Cl22NaCl

7. How to balance chemical equations. The big numbers next to the elements or compounds are called coefficients. These are the only things we can change in a chemical equation. 2Na + Cl22NaCl

8. How to balance chemical equations. Coefficients tell us the amount of each compound or element we have. You multiply the subscript for each element to the right of a coefficient until you are stopped by a + or  2Na + Cl22NaCl

9. How to balance chemical equations. So in this equation you have 2 x 1 sodium atoms being added to 2 chlorine atoms yielding 2 x 1 sodium chloride molecules. 2Na + Cl22NaCl

10. How to balance chemical equations. When we balance chemical equations, we need to figure out what coefficients to use. ___H2 + ___O2___H2O

11. How to balance chemical equations. To do that, we list how many atoms of each element we start with, then use math to figure out the coefficients. ___H2 + ___O2___H2O

12. How to balance chemical equations. In this equation, we start with: ___H2 + ___O2___H2O

13. How to balance chemical equations. Our hydrogen is balanced, but we don’t have enough oxygen in the product. ___H2 + ___O2___H2O

14. How to balance chemical equations. We need to make our best mathematical guess as to which coefficient will bring balance to the equation. ___H2 + ___O2___H2O

15. 2 How to balance chemical equations. We need two oxygen atoms, so lets try a coefficient of 2 in front of the product. ___H2 + ___O2 ___H2O

16. 2 How to balance chemical equations. Multiply that 2 by the subscripts for each atom in the product. ___H2 + ___O2 ___H2O 4 2

17. 2 How to balance chemical equations. Now we have enough oxygen, but too much hydrogen. How do we balance it? ___H2 + ___O2 ___H2O 4 2

18. 2 2 How to balance chemical equations. If we put a coefficient of 2 in front of the H2 on the reactants side, we can balance the equation. ___H2 + ___O2 ___H2O 4 4 2

19. How to balance chemical equations. Multiply the number of atoms you have by coefficients to balance equations. Multiply coefficients by every subscript until you hit a + or a . Never, ever, EVER change a subscript. Make a list of how much of each atom you have and change it as you add coefficients to your equation. If there are poly-atomic ions on both sides of your equation, don’t separate them!

20. Quick Check ___Al(OH)3 + ___H2SO4___Al2(SO4)3 + ___ H2O