1. Measurement & Significant Figures
Mrs. Page

2. By the end of this lesson you should be able to:
Distinguish between exact and measured numbers.
Identify different pieces of lab equipment, what it measures & the units of measurement
State the SI units for mass, length, volume, temperature, and amount of a substance.
Use a ruler, graduated cylinder, triple beam balance to make accurate measurement (to correct place value)

3. By the end of this lesson you should be able to:
Explain how a measured number tells the audience about the accuracy of the tool used to make a measurement
Determine the number of significant figures in a given number
Perform calculations & express solutions with correct number of significant figures

4. 2 Types of Numbers
Exact
Measured

5. Exact Numbers (3 types)
Counting objects are always exact 2 soccer balls 4 pizzas
Exact relationships such as conversion factors 1 foot = 12 inches 1 meter = 100 cm
Constants/ By Definition Pi, Avogadro’s #, speed of light

6. Measured Numbers
Measured numbers will always include some degree of ERROR
An instrument is used for measuring and therefore the user must at some point estimate the value.
When you use your calculator to calculate using a measured number your answer can only be as accurate as your worst measurement.

7. Learning Check
A. Exact numbers are obtained by 1. using a measuring tool 2. counting 3. definition B. Measured numbers are obtained by

8. Learning Check Classify each of the following as an exact or a
measured number.
1 yard = 3 feet
The diameter of a red blood cell is 6 x 10-4 cm.
There are 6 hats on the shelf.
Gold melts at 1064°C.

9. Metric System Every measurement has 2 parts:
Number
Unit (scale)
SI System (le Systeme International) is based on the metric system
Prefix + Base Unit
Prefix tells you the power of 10 to multiply by (easy for conversions)

10. SI Units Measuring Base Unit Symbol Mass Kilogram kg Volume (solid)
(liquid)
Cubic centimeter
Liter
cm3 L
Length
Meter m
Time
Second s
Temperature
Kelvin K
Amount of Substance
Moles
mol
Force
Newton N

11. Important Prefixes Prefix Symbol Amount Scientific Notation Giga - G
1,000,000,000
109
Mega - M
1,000,000
106
Kilo - k
1,000
103
Deci d
0.1
10-1
Centi - c
0.01
10-2
Milli - m
0.001
10-3
Micro -
10-6
Nano- n
10-9

12. Dimensional Analysis
Coming to a lesson soon

13. Tool: Ruler Measures length Measures in centimeter (cm)
All measurements have a degree of uncertainty!
We can see the markings between cm
We can’t see the markings between the
We must “guess” between 0.6 & 0.7
We record 1.67 cm as our measurement
The last digit an 7 was our guess...stop there

14. What is the measure? What is the length of the wooden stick? 1) 4.5 cm

15. What is the measure in cm?

16. Beaker Measures Volume This tool measures in milliliters (mL)
Not very accurate (what is the interval?)

17. Conical (Erlenmeyer) Flask
Measures volume
Units – mL
Used when heating to avoid splashing and/or to collect gasses
Accurate???

18. Graduated Cylinder
Measures Volume
Units – mL
Accurate???

19. Reading a Graduated Cylinder
Avoid Parallax Error
Meniscus

20. What is the level of uncertainty?
To what place value should we record an answer?
MUST look at INTERVAL
17.6mL

21. Reading a Graduated Cylinder

22. Which Gives the MOST Accurate Measure? Why?

23. Triple Beam Balance
Measures Mass
This tool measures in grams (g)

24. Reading a Balance

25. Electronic Scale Measures mass in grams (g) Digital equipment
Note all digits recorded
Uncertainty should be on equipment
Often must be calibrated

26. BRAIN BREAK

27. Significant Figures
Numbers that are important for performing calculations to ensure that your final answers are accurate
There are many significant figure rules

28. THE RULES All non-zero numbers are significant Examples: 65.23 23,456
4 sig. figs.
23,456
5 sig. figs.
7 sig. figs

29. THE RULES All zeros between two non-zero numbers are significant
Examples:
2014
4 sig. figs
300,002
6 sig. figs
1.0005
5 sig. figs.

30. THE RULES Place holder zeros are NOT significant
Leading zero - before any digits
0.0012
2 sig. figs
Trailing zeros – after digits but BEFORE a decimal
345,000
3 sig. figs
41,980,000.
4 sig. figs

31. THE RULES
All zeros at the end of a number and AFTER the decimal point are significant
Examples:
5.0000
5 sig figs
402.0
4 sig figs
0.450
3 sig figs

32. THE RULES Significance of a DECIMAL point MUST PAY ATTENTION
Try some more as Mrs. Page puts them on the board.
QUESTION???? ASK NOW!!!!

33. Calculations w/ Sig. Figs.
RULE 1. In carrying out a multiplication or division, the answer cannot have more significant figures than either of the original numbers. (answer has # of sig. figs of smaller # of sig figs)

34. Calculations w/ Sig. Figs.
RULE 2. In carrying out an addition or subtraction, the answer cannot have more digits after the decimal point than either of the original numbers.