 Measurement Lab, Sig Figs, SI Units, Book Distribution Chem GT 9/1-2/15

Drill  If you didn’t finish taking measurements, you have 5 more minutes now.  Put the What Not To Do Lab sheet on your desk, answer side up.  How should you smell a chemical?  HW:  Finish Significant Figures WS (back)  4A – Get SI Unit PPT notes from website (maybe)  Metric System Scavenger Hunt WS (do on your own, rather than in a group)

Objectives  IWBAT  Explain correct safety procedures.  Measure with great precision  Explain and use significant figures for taking measurement, interpreting measurements, and calculating with measurements  Use the SI Units system to correctly describe measurements

Agenda  Drill  Questions for me!  HW Review  4A – Finish Measurement Lab, Part I  4A – Significant Figures Notes  Measurement Lab, Part II  Book Sign-Out  SI Units Notes – 4A– if we don’t get to these, they are on my website—get the NOTES!  Closure – 2 part

Questions/Concerns  Sorry, there isn’t time to change your STEM fair topic, and yes, you should be gathering data. If you’re without a project (transferred, Bio & Chem, etc), see me at the end of class! If you need something approved, you MUST turn a revised version in to me by Friday/Thursday.  There are plenty (PLENTY) of other assignments other than STEM Fair this year.  No, I didn’t win on Jeopardy!  But I had a great time!  No, you don’t have to memorize the Periodic Table, but you will end up learning quite a lot of it by simple use.  I’ve read part of the Wheel of Time series, but it wasn’t exactly my cup of tea. I prefer Mercedes Lackey and Anne McCaffrey.  Other questions?

HW Review  Any questions from the What Not to Do Lab?  Collect Precision & Accuracy Lab

Measurement Lab – 4A  Let’s return to the measurement lab

Measurement Lab  Do all of your measurements have the same number of digits?  What determines the number of digits you write down?

What are Significant Figures??  Please work with a partner to complete “What are Significant Figures??” WS. You will be deriving rules to govern numbers!

Measuring Devices  When you take a measurement, you record all of the digits that can be recorded directly, and then estimate ONE MORE DIGIT.  Those are your significant figures (or significant digits)  Adding more is just making it up!  Recording less is doing your data a disservice.  Respect your data!

Measurements Determine Significance  Read the temperature on the thermometer.  Is it:  75°C?  74°C?  74.2°C?  How carefully CAN you read it?  The instrument itself determines the significance.

Rules for Determining the number of Significant Figures in a Given Measurement  If you are given a measurement (i.e. YOU did not measure it), you follow these rules to calculate the number of sig. figs.:  All non-zero digits are sig. figs (ex , )  Final zeros to right of decimal are sig. figs (ex. 1. 0, )  Zeros surrounded by significant figures are significant (ex , 1 0 2, )

Record Number of Significant Figures in Each Measurement

Practice  Use Significant Figures WS to practice with determining numbers of Sig Figs – front  4B

Rule for Addition and Subtraction with Sig. Figs.  Round the sum or difference so that it has the SAME number of DECIMAL PLACES as the measurement having the FEWEST decimal places.  ex = 6.22 =  correct answer shown in red box;  what you get on your calculator shown in italics ex = = ex = = ex = 3 =

Rule for Multiplication & Division with Sig. Figs.  Express a product or quotient to the same number of significant figures as the multiplied or divided measurement having the fewer total significant figures.  ex = =  correct answer shown in red box;  what you get on your calculator shown in italics 70.4 (3 sig. figs.) 210 (2 sig. figs.) ex  45 = =

1) g g g 2) L - 2.3L =  A. 347g  B g  C g  A L  B. 0.7 L  C L

Example m x 82.7 m = a) m 2 b) 432 m 2 c) m 2 d) 430 m 2 Example 2 d = 23 g / 4.44 cm 3 = a) g/cm 3 b) 5.18 g/cm 3 c) 5.2 g/cm 3 d) 5 g/cm 3

Infinite Number of Significant Digits  Some quantities have an infinite number of significant figures because they are definitions rather than measurements.  Example, by definition 1 meter = …..cm

Measurement Lab, Part II  Make sure you are taking your measurements with a high degree of precision.  Record the number of sig figs in the third column  I’ll be calling you to sign out books.

The Measurement System of Science  Do these mean anything to you?  Kilo:  kilometer, kilogram  Centi:  centimeter, cents, century  Deca  Decathlon, decade

Brainstorm  What other metric units/prefixes do you know?  Let’s make a list!

Base Units  The International System (SI -- Le Système International d’Unités) has seven base units:  Length (meter - m)  Mass (kilogram - kg)  Time (second - s)  Amount of a substance (mole - mol)  Temperature (kelvin - K)  Electric Current (ampere - A)  Luminous Intensity (candela - cd)  ADD Volume (liter – L) – not really an SI unit!

Prefixes – give meaning!  There are eight prefixes that you will need to know for the SI units: Abbrev.  Mega (1,000,000 x base;M 1 mega-base = base)  kilo (1000 x base; 1 kilo-base = 1000 base) k  hecta (100 x base; 1 hecta-base = 100 base) h  deka (10 x base; 1 deka-base = 10 base) da  deci (base/10; 10 deci-base = 1 base) d  centi (base/100; 100 centi-base = 1 base) c  milli (base/1000; 1000 milli-base = 1 base) m  micro (base/ ;  /u micro-base = 1 base)

So what? How do we use them?  Any SI unit has two parts:  prefix  base  For example,  kilo - gram  kilo - mete r  centi - meter  centi - gram  So, what do we call 10 grams?  deka - gram  What do we call.001 seconds?  milli - second  How about.1 liters?  deci - liter

Closure – Part 1 Identify the number of sig figs in each of these measurements: g m m 4. 9,000,010 s

Closure – Part 2  Brainstorm an item (any item other than Ms. Bloedorn’s examples) that has, approximately:  mass of one gram  volume of one liter  time of one second  distance of one kilometer  FYI, 1 km = 0.62 mi, 1 kg = 2.2 lb