Transcript 9/1-2 Fin Meas Lab, Sig Figs, SI Units

Measurement Lab, Sig
Figs, SI Units, Book
Distribution
Chem GT 9/1-2/15
S
Drill
S If you didn’t finish taking measurements, you have 5
more minutes now.
S Put the What Not To Do Lab sheet on your desk,
answer side up.
S How should you smell a chemical?
S HW:
S Finish Significant Figures WS (back)
S 4A – Get SI Unit PPT notes from website (maybe)
S Metric System Scavenger Hunt WS (do on your
own, rather than in a group)
Objectives
S IWBAT
S Explain correct safety procedures.
S Measure with great precision
S Explain and use significant figures for taking
measurement, interpreting measurements, and
calculating with measurements
S Use the SI Units system to correctly describe
measurements
Agenda
S Drill
S Questions for me!
S HW Review
S 4A – Finish Measurement Lab, Part I
S 4A – Significant Figures Notes
S Measurement Lab, Part II
S Book Sign-Out
S SI Units Notes – 4A– if we don’t get to these, they are on my
website—get the NOTES!
S Closure – 2 part
Questions/Concerns
S 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.
S There are plenty (PLENTY) of other assignments other than STEM Fair this
year.
S No, I didn’t win on Jeopardy!  But I had a great time!
S No, you don’t have to memorize the Periodic Table, but you will end up
learning quite a lot of it by simple use.
S 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.
S Other questions?
HW Review
S Any questions from the What Not to Do Lab?
S Collect Precision & Accuracy Lab
Measurement Lab – 4A
S Let’s return to the measurement lab
Measurement Lab
S Do all of your measurements have the same number of
digits?
S What determines the number of digits you write down?
What are Significant Figures??
S Please work with a partner to complete “What are
Significant Figures??” WS. You will be deriving rules
to govern numbers!
Measuring Devices
S When you take a measurement, you record all of the
digits that can be recorded directly, and then estimate
ONE MORE DIGIT.
S Those are your significant figures (or significant digits)
S Adding more is just making it up!
S Recording less is doing your data a disservice.
S Respect your data!
Measurements Determine
Significance
S Read the temperature on the
thermometer.
S Is it:
S
S
S
S
75°C?
74°C?
74.2°C?
How carefully CAN you read it?
S The instrument itself determines
the significance.
80
70
60
50
40
30
20
10
0
Rules for Determining the number
of Significant Figures in a Given
Measurement
S If you are given a measurement (i.e. YOU
did not measure it), you follow these rules
to calculate the number of sig. figs.:
S All non-zero digits are sig. figs (ex. 1.2300,
3004)
S Final zeros to right of decimal are sig. figs (ex.
1.0, 1.2300)
S Zeros surrounded by significant figures are
significant (ex. 1.2300, 102, 3004)
Record Number of Significant
Figures in Each Measurement
23.0
______ 23.00
0.123
______ 0.0123 ______ 0.00123 ______
102
______
1002
______ 23.004 ______
______ 102.030 ______
Practice
S Use Significant Figures WS to practice with
determining numbers of Sig Figs – front
S 4B
Rule for Addition and
Subtraction with Sig. Figs.
S Round the sum or difference so that it has the SAME
number of DECIMAL PLACES as the measurement
having the FEWEST decimal places.
6.2
ex. 73 - 2.341 = 70.659 = 71
ex. 1001 - 0.099 = 1000.901 = 1001
ex. 2.94 + 0.06 = 3 = 3.00
S ex. 2.7 + 3.52 = 6.22 =
S correct answer shown in red box;
S what you get on your calculator shown in italics
Rule for Multiplication &
Division with Sig. Figs.
S Express a product or quotient to the same number of
significant figures as the multiplied or divided
measurement having the fewer total significant figures.
70.4 (3 sig. figs.)
ex. 9574  45 = 212.7555556 = 210 (2 sig. figs.)
S ex. 32.43 • 2.17 = 70.3731=
S correct answer shown in red box;
S what you get on your calculator shown in italics
1)
+
4.375 g
14.62 g
327.9
g
S A. 347g
S B. 346.895g
S C. 346.9g
S A. 0.7024 L
2) 3.0024L - 2.3L =
S B. 0.7 L
S C. 0.70 L
Example 1
Example 2
5.22 m x 82.7 m =
d = 23 g / 4.44 cm3 =
a) 431.694 m2
a) 5.18018018 g/cm3
b) 432
m2
c) 431.7
m2
d) 430 m2
b) 5.18 g/cm3
c) 5.2 g/cm3
d) 5 g/cm3
Infinite Number of Significant
Digits
S Some quantities have an
infinite number of
significant figures because
they are definitions rather
than measurements.
S Example, by definition 1
meter = 100.000 00…..cm
Measurement Lab, Part II
S Make sure you are taking your measurements with a
high degree of precision.
S Record the number of sig figs in the third column
S I’ll be calling you to sign out books.
The Measurement System of Science
S Do these mean
anything to you?
S Kilo:
S kilometer, kilogram
S Centi:
S centimeter, cents,
century
S Deca
S Decathlon, decade
Brainstorm
S What other metric units/prefixes do you know?
S Let’s make a list!
Base Units
S The International System (SI -- Le Système
International d’Unités) has seven base units:
S Length (meter - m)
S Mass (kilogram - kg)
S Time (second - s)
S Amount of a substance (mole - mol)
S Temperature (kelvin - K)
S Electric Current (ampere - A)
S Luminous Intensity (candela - cd)
S ADD Volume (liter – L) – not really an SI unit!
Prefixes – give meaning!
S There are eight prefixes that you will need to know for the SI units:
S Mega (1,000,000 x base;
S
S
S
S
S
S
S
1 mega-base = 1000000 base)
kilo (1000 x base; 1 kilo-base = 1000 base)
hecta (100 x base; 1 hecta-base = 100 base)
deka (10 x base; 1 deka-base = 10 base)
deci (base/10; 10 deci-base = 1 base)
centi (base/100; 100 centi-base = 1 base)
milli (base/1000; 1000 milli-base = 1 base)
micro (base/1000000;
1000000 micro-base = 1 base)
Abbrev.
M
k
h
da
d
c
m
/u
So what? How do we use them?
S Any SI unit has two parts:
S prefix
S base
S For example,
S kilo-gram
S kilo-meter
S centi-meter
S centi-gram
S So, what do we call 10 grams?
S deka-gram
S What do we call .001
seconds?
S milli-second
S How about .1 liters?
S deci-liter
Closure – Part 1
Identify the number of sig figs in each of these
measurements:
0.01209 g
2. 200 m
3. 209 m
4. 9,000,010 s
1.
Closure – Part 2
S Brainstorm an item (any item other than Ms.
Bloedorn’s examples) that has, approximately:
S mass of one gram
S volume of one liter
S time of one second
S distance of one kilometer
S FYI, 1 km = 0.62 mi, 1 kg = 2.2 lb