1. Ch. 6: Chemical Reactions
Chemical reactions are everywhere!
Fires burn, grass grows, joggers run, milk sours
In a chemical reaction one or more substances change into different substances
Equations are used to describe chemical reactions
Word equations: names of the chemicals
Chemical equations: formulas represent chemicals

2. During a chemical reaction, reactants collide allowing their atoms or ions to rearrange to form products
Reactants: the substances that are used up during the reaction
Products: the substances that are produced during the reaction

3. Example 1: Reactants -> Products
Word equation: iron + sulfur -> iron(II) sulfide + energy
Chemical equation: Fe S -> FeS energy
Example 2: State Symbols Included
energy + copper(II) carbonate -> carbon dioxide + copper(II) oxide
energy CuCO3 (s) -> CO2 (g) CuO(s)
Example 3
zinc copper(II) sulfate - > zinc sulfate copper
Zn(s) CuSO4(aq) -> ZnSO4(aq) Cu(s) energy
Remove slide contents before printing! Chemical reactions can either absorb or release energy, 1. releases more energy than is absorbed, therefore it is a product, 2. copper(II) carbonate absorbs energy to produce carbon dioxide gas and copper(II) oxide
State symbols, s, g, l, aq

4. Conservation of Mass MASS IS CONSERVED DURING CHEMICAL REACTIONS
What about a fire?
Wood burns down to fluffy ashes that have much less mass than the original wood
Answer:
Some products are gases which have mass and they diffuse away
Antoine Lavoisier - conservation of mass 4:40 min

5. Law of Conservation of Mass: in any given chemical reaction, the total mass of the reactants equals the total mass of the products
The atoms in reactant compounds are rearranged to form product compounds
Therefore, all the atoms that existed in the reactants are still present in the products of the reaction
Atoms cannot be created or destroyed

6. Chemical equations much follow the law of conservation of mass!
It must show an equal number of each kind of atom on both sides of the equation
Meaning, there are equal numbers of each kind of atom before and after the chemical reaction takes place
Steps for balancing chemical equations:
1. Write the word equation 2. Write the chemical equation 3. Count the number of atoms of each type on each side 4. Multiply the formulas by coefficients until balanced
Homework: page 236 #7 (if lots of time #5,6,7 also)