1. Do Now & Announcements Grab a Handout (for after the quiz)
Turn in HW to be checked
Clear desks and prepare for quiz
Unit 1 Test MON 8/31

2. Units
*Unit= any standard that is used for comparison in numbers or measurement
Whenever you report a measurement, you report a number followed by the unit

3. System International (SI) Units: an international system of measurement based on the metric system. Some common ones we’ll be working with are:
Measurement
Base Unit
Symbol
Length
meter
Mass
gram
Volume
Liter
Temperature
Kelvin
Energy
Joule
Frequency
Hertz
Pressure
Pascal
Amount of Substance
Mole
Density
grams/milliliter or
grams/centimeter3 m g L K J Hz Pa
mol
g/mL or
g/cm3

4. Prefixes: placed before the base unit to indicate a larger or smaller quantity; based on powers of 10.

5. x1000
x10
x10
x10
x10
x10
x10
x1000
x1000
Prefixes at the top of the chart represent a larger amount or quantity.
Prefixes at the bottom of the chart represent a smaller amount or quantity.  

6. Accuracy vs. Precision

7. Accuracy vs. Precision
Accuracy=how close the results are to the correct answer (Bull’s eye!)
To determine accuracy, we look at the average of our results.
Precision= how often the same results are measured/obtained
To determine precision, we look at the consistency of our results.

8. AVERAGE
ACCURATE NO

9. each trial/measurement
precise NO

10. Accuracy vs. Precision Practice
YES
YES

11. Accuracy vs. Precision Practice
4.67 NO 99
YES
YES NO

12. Percent Error
A quantitative way we can look at the accuracy of a set of data if the true value is known
For this class, we’ll say the data is accurate if the percent error is less than 5%

13. The freezing point of water is 273. 2 K, but it was measured at 250
The freezing point of water is K, but it was measured at K. What is the percentage error?
Calculate the top part first, then divide!
×100%
250.1− ×100%=
=0.084×100%
=𝟖.𝟒%
NOT ACCURATE

14. Percent Error Practice
2) 4.49 % 3) 888% 4) 3.88%

15. Measurement: When using tools with graduated “tick marks”, you should estimate one decimal place beyond the value of the smallest tick mark!
0.7 cm
Each tick mark represents 1 cm
 round to nearest 0.1 cm

16. Each tick mark represents 0.1 cm
 round to nearest 0.01 cm

17. Reading Graduated Cylinders:
Liquids form a curved surface when in graduated cylinders. As a standard, you should read the liquid level from the bottom of the meniscus