 Safety Video & Tour Math Assessment Review Measurement and Sig Figs Chem GT 8/28-31/15

Drill  Classify these sets of data as precise or accurate or both:  Set 1: 2.3mL, 3.4mL, 1.2mL  Correct value=2.3 mL  Set 2: 9.8cm, 9.9cm, 9.8cm  Correct value=9.5cm  Set 3: 1.02g, 1.01g, 1.01g  Correct value=1.02g

Objectives  IWBAT  Explain correct safety procedures.  Review the math concepts required for Chem GT  Measure with great precision  Review math concepts  HW:  What Not To Do Laboratory WS, get Safety Contract signed  Finish Precision & Accuracy Lab, if needed  Gather data for STEM Fair!!!

Pd. 4A – Precision & Accuracy Lab  Let’s discuss the percent error.  What could have gone wrong? Let’s discuss sources of error.  Go back and gather data for part 2. Record your percent error on the board.  Work on questions until everyone is done with part 2.

Missing Forms – Pd. 4A  You’re doing a great job!  Erik Irby

Missing Forms – 4B  Great job!  Parent Confirmation:  Ryan

Math Assessment  You have gotten back the math assessment. It was graded out of 24 points, in your homework/classwork category.  Let’s go over your questions!  Pass in the Exponent Math HW

Safety  Let’s watch a safety video.  mYme6Y mYme6Y  We will also do a safety “tour” of the room and look at the safety contract.  Do you know what to do for the drills?  Fire? Duck, cover, and hold? Lockdown?

Measurement Lab  You will be filling out the FIRST column, only.  Please take the measurements with the highest degree of precision possible.

Measurement Lab  Do all of your measurements have the same number of digits?  What determines the number of digits you write down?  4A

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

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, )

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.

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!

Record Number of Significant Figures in Each Measurement

Practice  Use Significant Figures WS to practice with determining numbers of Sig Figs

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

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