1. Balancing Equations

2. What is the law of conservation of mass?
In any physical change or chemical reaction, mass is conserved; mass can be neither created nor destroyed
What is the law of conservation of mass?

3. Why do we balance equations?
We must show the law of conservation of mass.
For example:
Manufacturing a bicycle you have a frame, handlebars, wheels, and pedals
Frame + wheel + handlebars + pedal  bicycle
reactants product
F + W + H + P  FW2HP2
This is not balanced; it does not tell us how much of the reactants are needed to make the product.
Why do we balance equations?

4. Why do we balance equations?
subscripts
coefficient
coefficient
Why do we balance equations?

5. Rules for balancing equations
Determine the correct formulas for all the reactants and products.
Write the skeleton equation by placing the formulas for the reactants on the left and the formulas for the products on the right side with a yields sign ( ) in between. If two or more reactants or products are involved, separate their formulas with plus signs.
Rules for balancing equations

6. Rules for balancing equations
Determine the number of atoms of each element in the reactants and products. Count a polyatomic ion as a single unit if it appears unchanged on both sides of the equation.
Balance the elements one at a time by using coefficients. When no coefficient is written, it is assumed to be 1. Begin by balancing elements that appear only once on each side of the equation. Never balance an equation by changing the subscripts in a chemical formula. Each substance has only one correct formula.
Rules for balancing equations

7. Rules for balancing equations
Check each atom or polyatomic ion to be sure they are equal on both sides of the equation.
Make sure all the coefficients are in the lowest possible ratio.
Rules for balancing equations

8. Examples and Independent Practice

9. Why do we (in science) classify information?