CHEMISTRY TUESDAY, 9/15 As you come into class, please take out: 1.your significant figures notes from last class 2.Something to write with 3.Calculator 4.Sig Fig practice (purple, up front)

SIG FIG CALCULATIONS 1.Read over the calculation rules with your partner  Addition & subtraction  Multiplication & division 2.Complete these practice problems worksheet. Work with your partner!  Check your answers when you’re done.

DIMENSIONAL ANALYSIS In which you will learn about: Conversion factors Standard dimensional analysis Dimensional analysis with exponential units

Dimensional Analysis is a way chemists and other scientists convert units of measurement. We can convert any unit to another unit of the same dimension. That means we can convert some number of seconds into another unit of time, such as minutes, because we know that there are always 60 seconds in one minute. Or we can convert some amount of mass from grams to kilograms, knowing that there are always 1000 grams in one kilogram. Or we can convert lengths, say, from kilometers to miles, although metric units are most frequently used in chemistry. With a known conversion factor, it is sometimes possible to convert to a new dimension. For instance, 1 kilogram of pure water is equal to 1 liter. Using that knowledge, you could convert a volume of pure water to a mass of water, or vice versa. DIMENSIONAL ANALYSIS

DIMENSIONAL ANALYSIS PACKET  Underline or highlight the definition of “SI” units (p. 587).  Underline or highlight the “equivalencies” in the example problems (p.588).  To solve calculations, these equivalencies convert into “conversion factors”. Box ALL of the conversion factors in both example problems (p.588).  Complete #2 on page 589

PROBLEM #3 (p.589) – An antacid tablet contains 168 mg of the active ingredient ranitidine hydrochloride. How many grams of the compound are in the tablet? 1) Find your “given” piece of information in the problem and underline it. Given: 168 mg 2) Find your “unknown” piece of information (or what you are trying to find) and box it. Unknown: ? grams 3) Determine your equivalencies. Do we know how many milligrams are in a gram? 1 gram = 1000 mg DIMENSIONAL ANALYSIS PACKET

Hint! Use the one that will cancel out the units you want to change DIMENSIONAL ANALYSIS PACKET

 There are a few more practice problems for you to look over on page 592. Take a look at those and walk through them with your partner.  Ok. Now try #1 on page 593 with your partner. Answer: 4,741 km  Make sure you are showing your work correctly. Check your answer with mine.  Don’t forget about significant figures! Look back at your rules for performing calculations to make sure you are getting the correct answer. DIMENSIONAL ANALYSIS PACKET

 Complete #2-3 on p.593 and check your answers up front.  Complete #5 & #7 on p.590 and check your answers up front. DIMENSIONAL ANALYSIS PACKET

PICK UP YOUR HOMEWORK Unit 1 Worksheet 6 (yellow) is due next class.