1. Accuracy –
Precision -

2. Percent Error

3. Practice
A student estimated a mass to be 250 grams, but upon carefully measuring it, found the actual mass to be 240 grams. What is the percent error?
2. The experimental calculation of the specific heat of aluminum was found to be .156 cal/g◦C, but the actual value was given as .185 cal/g◦C. What is the percent error?

4. Practice
Joe measured the volume of an object 5 times, and got the results of: 34.5 mL, 34.9 mL, 34.2 mL, 33.4 mL, and 35.9 mL. What is his average experimental value?
2. The actual volume of the object was 34.1 mL. What is the percent error of his average result?
3. A student’s calculation was found to have a 15.6% error, and the actual value was determined to be 25.7 mL. What are two possible values for the student’s experimental measurement?

5. Scientific Notation
Why use it?

6. Practice Write the following in scientific notation:
61,500
321
64,960,000
Express in standard form:
x108
9.004 x10-2

7. Significant Figures Rules: Every non-zero digit is significant.
Zero’s in between non-zero digits are significant.
Leading zeros are not significant.
Zeros that are at the end of a number and to the right of a decimal are significant. (ex: or have four sig figs)
Ending zeros without a decimal are not significant (ex: has one sig fig)

8. Practice
1234
0.023
890
91010
9010.0
3.4 x10-4
9.010 x10-2

9. Addition and Subtraction
Round to the same number of decimal places as that of the numberin the calculation with the least decimal places.
2.5 cm cm cm
416 g g

10. Multiplication and Division
Round to the same number of significant figures as the number with the least number of significant figures.
0.020 cm x 50 cm x 11.1 cm
0.530 g / mL

11. SI Units SI Measurement System
• Le Systeme International d’Unites : SI
• System of measurement agreed on by scientists from all over the world in 1960 (related to the metric system)
• A decimal system based on 10
• Contains 7 base units and its units are defined in terms of standards of measurement that are objects or natural occurrence that are of constant value or are easily reproducible
• We still use some non-SI units

12. Exact or Measured Numbers
Exact examples: number of eggs in a carton, 1000 milliliters in a liter, cm in an inch, etc.
Measured examples: volume of a substance measured in a graduated cylinder, temperature of a liquid recorded using a thermometer.
Known digit plus one estimated digit

13. Base Units Measurement Metric SI Length meter (m) meter (m)
Volume liter (L) cubic meter (m3)
Mass gram (g) kilogram (kg)
Time second (s) second (s)
Temperature Celsius (°C) Kelvin (K)

14. Temperature Measure of how hot or cold something is.
Temperature determines the direction of heat transfer.
Celsius based upon freezing and boiling point of water
Kelvin developed from Lord Kevin (physicist and mathematician) –based on absolute zero.
K= C◦
C◦ = K –

15. k h da B d c m

16. Format for Conversions

17. Practice How many seconds are in 8 hours?
Students need 1.84 grams of copper wire to perform an experiment. The lab has a 50 gram spool of copper wire. How many students can perform the experiment?
Express 750 dg in grams.

18. Practice
What is cm in micrometers?
What is 49◦C in Kelvin?