1. Measurements in Experiments
1.2 pp 10-19
Mr. Richter

2. Agenda Turn in Posters Notes (Day 1): Warm-Up
Measurement
The Metric System (SI)
Discuss Energy Paragraphs
Metric Prefixes and Scientific Notation
Finish Yesterday’s Notes
Day 2:
Questions about the Quiz?
Accuracy
Introduction to the Metric System
Precision
Significant Figures

3. Objectives: We Will Be Able To…
List basic SI units and the quantities they describe.
Convert measurements into scientific notation.
Distinguish between accuracy and precision.
Use significant figures in measurements and calculations.

4. Warm-Up:
There are 5280 feet in a mile. There are 1000 meters in a kilometer.
How many feet are in 4 miles?
How many meters are in 4 kilometers?

5. For Tomorrow’s Quiz You Should:
Review your notes
Review the slides online
Pay special attention to things I have repeated
(Like vocab, objectives, homework problems…)
Bring a sharpened pencil and be ready to go at the bell tomorrow

6. Measurement

7. What are Measurements?
Measurements tell us how much of what kind of stuff we have.
Measurements require two things:
A quantity – how much
A dimension (units) – what kind
UNITS MATTER!
My amount of wealth differs greatly if I have 30 million dollars or 30 million yen
I can’t say “I live four away from here.” It only makes sense if I say “four miles” or “four kilometers”.

8. Système Internationale (SI) aka The Metric System
All scientists and most countries use the SI or metric system.
Why?
Because it is easy to convert between large and small units.
And to use scientific notation.
The SI system has three base units (p. 11):
Meter – length
Kilogram – mass
Second – time
All other units are combinations or derivations of these three.

9. Metric Prefixes
The SI uses metric prefixes and scientific notation to accommodate extreme values of the base units.
You will be required to memorize:
nano-
micro-
milli
centi
kilo-
mega-

10. Homework for Tonight
p14 #1-5

11. Warm-Up Work by yourself in your notes to answer each question.
Remember to think in terms of being realistic: are meters larger or smaller than the original unit?
If you can, try to do this from memory; without the prefix charts.
How many meters is:
42 kilometers
4.2 kilometers
0.42 kilometers
4200 centimeters
420 centimeters
42 centimeters
4.2 centimeters
Start here day 2.

12. Agenda Warm-Up Accuracy and Precision Review Quiz Significant Figures
Set Up Portfolios
Review Homework
More On Metric Conversions
Scientific Notation

13. Objectives: We Will Be Able To…
List basic SI units and the quantities they describe.
Convert measurements into scientific notation.
Distinguish between accuracy and precision.
Use significant figures in measurements and calculations.

14. Converting with Metric Prefixes (Another Method)
1 mm = 10-3 m, therefore:
To convert between units, multiply by the conversion factor.
Make sure units cancel out.
Bad:
Good:

15. Using Units
Units must agree. A fancy way of saying that the units used to express a measurement must match.
For example:
Don’t use kilograms to measure length. Duh.
Sometimes people will use different units of distance to measure the same thing, like area. Avoid and convert:
feet-meters
centimeter-meters

16. Scientific Notation
Review

17. Scientific Notation
Used in conjunction with metric prefixes to indicate the size of a measurement.
To convert to scientific notation:
slide decimal point to the right of the first non-zero value
 3.45 
then multiply by a power of 10 to compensate for the shifted decimal point
 3.45 x 10-4
 x 105

18. Your Turn Convert the following values into scientific notation: 4200
340.6
0.02
How did you do?
4.2 x 103
3.406 x 102
2 x 10-2
6.50 x 10-3

19. Warm-Up Express the following measurements in scientific notation:
346 meters
2400 grams
meters/second
How did you do?
3.46 x 102 m
2.4 (or 2.40 or 2.400) x 103 g
1.8 x 10-3 m/s

20. Scientific Notation
The real reason for scientific notation: not just because we’re sick of writing zeros.
Scientific notation allows us to compare the sizes of numbers almost instantaneously.
Which number is bigger? or
How much easier is it in scientific notation?
2.3 x 1016 or 1.7 x 1017

21. Accuracy and Precision

22. Accuracy
Describes how close a measured value is to the true value of the quantity measured.
Errors in accuracy come from:
human error – incorrect use of instrument or science
using a tape measure incorrectly
reading a thermometer at the wrong level
instrument error – the device used to take a measurement doesn’t work
the tape measure or thermometer is broken

23. Precision
Refers to the degree of exactness with which a measurement is made and stated.
Errors in precision come from the limitations of an instrument, not human error or calibration.
For example: if the scale at the doctor’s office measures only to the nearest kilogram, then the doctor cannot be expected to state your mass to the nearest tenth of a kilogram.

24. Accuracy vs. Precision: Length
The length of a 18-cm pencil is measured three times with a ruler by three different people:
The length is measured to be about 18 cm each time: accurate but not precise.
The length is measured to be cm, cm, and cm respectively: precise but not accurate.
The length is measured to be cm, cm, and cm: both accurate and precise.

25. Significant Figures
What numbers matter? (Summary of rules pp )

26. Significant Figures (SigFigs)
Significant figures indicate the degree of precision with which a measurement was taken.
For example: 23 meters vs meters. What’s the difference?
The same number mathematically, but the latter is more precise. The measurement was taken with a more precise instrument.
Significant Figures comes down to: Which zeros don’t matter?
Any in front of non-zero digits:
Any at the end of a number but to the left of the decimal: 2000

27. Significant Figures and Scientific Notation
Scientific notation tells the difference between significant and insignificant figures.
For example: 200 could have 1 significant figure or 3.
In scientific notation:
200 = 2 x 102, or
200 = 2.00 x 102
It is easy to see which measurement is more precise written in scientific notation.

28. Calculations with Significant Figures
Adding: the sum should have the same number of digits to the right of the decimal as the least precise measurement.
≠ (indicates too much precision)
= 362
Multiplying: the product should have the same number of significant figures as the least precise measurement.
4.6 x 6.7 ≠ (indicates too much precision)
4.6 x 6.7 = 31
Note: Your calculator doesn’t get sig figs.

29. Your Turn
Try p. 28 #20, a-d

30. Wrap-Up: Did we meet our objectives?
List basic SI units and the quantities they describe.
Convert measurements into scientific notation.
Distinguish between accuracy and precision.
Use significant figures in measurements and calculations.

31. Homework
Due Wed:
p19 #1-4