Intro video

-shorthand way to describe chemical reactions using symbols and formulas Instead of writing: “When you add solid silver to hydrogen sulfide gas, you get solid silver (I) sulfide and diatomic hydrogen gas.” You can just write: Ag (s) + H 2 S (g) --> Ag 2 S (s) + H 2 (g)

 Reactants:  On the left side of the equation  Substances that are altered in the course of a chemical reaction (what you start with)  Products:  On the right side of the equation  New substances created as a result of a chemical reaction (what you end up with) →→  “Yeilds” or produces  Similar to an equal sign in an equation

“In a chemical reaction, matter (consisting of atoms) is not created or destroyed.”

– number placed in front of items in a chemical equation to tell how many of each are taking part in the reaction – Pb(NO 3 ) KI  PbI KNO 3

-equation with the same number of atoms of each element on both sides of the equation (atoms are rearranged) If you don't balance your equations, you're not following the law of conservation of mass! It looks like you're making or destroying atoms!

-To balance the equation, you CANNOT change subscripts. You can only change coefficients.

Does the following equation follow the law of conservation of mass? Explain your answer. Ag (cr) + H 2 S (g)  Ag 2 S (cr) + H 2(g)

Ag H S

H S

1. Coefficients will always be whole numbers. 2. Leave oxygen and hydrogen until last. 3. If you have to add coefficients to more than 1 item, leave single elements like Ag or H 2 4. If you get stuck, try balancing the metals first. 5. Make sure the equation is in the simplest form by reducing.

GCD = 2 Divide all coefficients by GCD (2) 4 Al + 3 O 2  2Al 2 O 3

2 H 2 O  2 H 2 + O 2 2 H 2 O  2 H 2 + 1O 2

O 2 + H 2  H 2 O NaOH  Na 2 O + H 2 O Ag 2 O  Ag + O 2