Mrs. Howland Chemistry 10 Rev. Jan 2016

Learners will know… The Law of Conservation of Mass as it relates to chemical changes of substances The parts of a chemical reaction Learners will be able to… Write and balance chemical equations Perform stoichiometry calculations

Chemical properties Chemical changes Chemical formulas Chemical bonding The MOLE Mole conversions CHEMICAL EQUATIONS Balancing chemical equations Stoichiometry Types of chemical reactions

Matter is neither created nor destroyed. In chemical reactions, the amount of particles in the reactants is equal to the amount of particles in the products.

Chemical reactions involve changes in the chemical composition of matter Creates new materials with new properties AMOUNT of matter does not change! Chemical equations describe a chemical reaction Written similar to a mathematical equation/is like a ‘RECIPE’

Reactants = Atoms or compounds that are changed in a chemical reaction (LEFT SIDE) Products = Atoms or compounds that are generated as a result of a chemical reaction (RIGHT SIDE)

SUBSCRIPTS = how many atoms or ions within a compound COEFFECIENTS = how many moles or formula units

Because of Law of Conservation of Mass, chemical equations MUST BE BALANCED BALANCED = same number of each kind of atom on both sides (reactants and products)

The TOTAL number of any given atom is equal to the COEFFECIENT x SUBSCRIPT H = 2 x 2 = 4

You MAY change the COEFFECIENTS You MAY NOT change the SUBSCRIPTS WHY NOT? Changing the subscripts changes the compound

There are FOUR basic steps 1. Write the correct formula for the reactants and the products ~ DO NOT TRY TO BALANCE IT YET! You must write the correct formulas first. **And most importantly, once you write them correctly DO NOT CHANGE THE FORMULAS! 2. Find the number of atoms for each element on the left side ~ Compare those against the number of the atoms of the same element on the right side.

3. Determine where to place coefficients in front of formulas ~ Left side must have same number of atoms as the right side for EACH element in order to balance the equation 4. Check your answer to see if: The numbers of atoms on both sides of the equation are now balanced The coefficients are in the lowest possible whole number ratios. (reduced)

Take one element at a time, working left to right except for H and O Try metals then nonmetals Save H for next to last, and O until last. IF everything balances except for O (there is no way to balance O with a whole number) double all the coefficients and try again. (Because O is diatomic as an element) (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units VIDEO: e.com/watch?v=UGf 60kq_ZDI e.com/watch?v=UGf 60kq_ZDI

Balance the following chemical equation: __C + __S 8  __CS 2

Use the simulation on this site to practice and re-learn the concepts LINK: chemical-equations-simulation/ chemical-equations-simulation/ DIRECT LINK: equations/latest/balancing-chemical-equations_en.html equations/latest/balancing-chemical-equations_en.html