The Mole Theory Dimensional Analysis

Dimensional Analysis A way to solve problems by converting or using the units of the items involved Converting one thing to the another – amount has not changed Used to solve problems in everyday life

Dimensional Analysis For example… 3 = 1 or just 1 Conversion factors: the numerator and denominator are equal so they are basically equal to ‘1’ – used to solve for unknowns in dimensional analysis problems For example… 3 = 1 or just 1 3 1 So if I have 2 x 3 = 6 where the 5 3 15 value is unchanged =

Dimensional Analysis Example Problem 1: How many seconds are in a day? What do we know? Set up Conversion Factors: Then we solve: × × = 86,400 sec 1 day

Dimensional Analysis Problem 2: You're throwing a pizza party for 15 and figure each person might eat 4 slices. How much is the pizza going to cost you? You call up the pizza place and learn that each pizza will cost you $14.78 and will be cut into 12 slices. You tell them you'll call back. How much money is the pizza going to cost you, which in math terms is: cost (in dollars) per party, or just $/party 14.78 x 4 x 15 = $73.90 12 party

Dimensional Analysis Tips for solving: Identify Known & Unknown (what do you know and what do you want to know?) Pick out conversion factors you may need to get from known to unknown Plug into the grid or rail road tracks – always start with the Known Work your way across so that tops and bottoms cancel with the one before it Stop when you get to units of the Unknown