1. Created by: Lauren Sniscak
SI System
Created by:
Lauren Sniscak

2. SI Units
In 1960, this international agreement was reached specifying particular choice of metric units for use in scientific measurements
Named after the French Système International d’Unités
Has 7 base units from which all other units are derived

3. SI Base Units Physical Quantity Name of Unit Abbreviation Mass
Kilogram kg
Length
Meter m
Time
Second
s, sec
Temperature
Kelvin K
Amount of substance
Mole
mol
Electric current
Ampere A
Luminous intensity
Candela cd

4. Prefixes Prefix Abbreviation Meaning Giga G 109 Mega M 106 Kilo k 103
Deci d
10-1
Centi c
10-2
Milli m
10-3
Micro μ
10-6
Nano n
10-9
Pico p
10-12
Femto f
10-15
Prefixes —
Used to indicate decimal fractions or multiples of various units

5. Mass Length Meter is the SI base unit
A distance only slightly longer than a yard
1m = 1.09yd
A measure of the amount of material in an object
Kilogram is the SI base unit
1kg = 2.20lb

6. Temperature Measure of hotness or coldness of an object
Determines the direction of heat flow
Always flows spontaneously from a substance of a higher temperature to one at a lower temperature
Celsius scale is the everyday scale of temperature in most countries

7. Temperature (cont.) Kelvin is the SI unit of temperature
Historically based on properties of gases
Zero is the lowest obtainable temperature on this scale
( oC): referred to as absolute zero
Kelvin and Celsius both have the same size degrees
K = oC + 273

8. Volume Cubic meter (m3) is the basic SI unit
Another commonly used unit of volume is liter (L)
1L = 1dm3
The liter is not an SI unit
1cm3 = 1mL
Those terms are used interchangeably in volume

9. Reading Volume Always read the volume at: Eye level
The Meniscus (bottom of the liquid curve)

10. Uncertainty in Measurement
Exact numbers-those whose values are known exactly
Have defined values
Result from counting numbers of an object
Inexact numbers-those whose values have some uncertainty
Always exists in measured quantities
Counting very large numbers of objects

11. Precision and Accuracy
Both terms are often used in discussing uncertainties of measured values
Precision-measure of how closely individual measurements agree with one another
Accuracy-refers to how closely individual measurements agree with the correct, or “true,” value

12. Precision and Accuracy (cont.)
Accuracy – closeness to “true” or accepted value
Percent error
Precision – many trials; reproducibility
Standard deviation

13. (cont.)

14. Significant Figures
Measured quantities are generally reported in such a way that only the last digit is uncertain
Significant figures-all digits of a measured quantity, including the uncertain one

16. Conceptual Problem 3.1 Counting Significant Figures in Measurements
1. How many significant figures are in each measurement?
a. 123 m d. 22 meter sticks
b. 40,506 mm e m
c x 104 m f. 98,000 m
Practice Problems
2. Count the significant figures in each length.
a meters c meter
b meters d meters
3. How many significant figures are in each measurement?
a. 143 grams c x 10-2 gram
b meter d. 1,072 meters

17. Sample Problem 3.1 Rounding Measurements
1. Round off each measurement to the number of significant figures shown in parentheses. Write the answers in scientific notation.
a meters (four)
b meter (two)
c meters (two)
Practice Problems
2. Round each measurement to three significant figures. Write your answers in scientific notation.
a meters d meters
b x 108 meters e x 10-3 meter
c meter f meters
3. Now round each measurement from 2. to one significant figure. Write each of your answers in scientific notation.

18. Sample Problem 3.2 Significant Figures in Addition
1. Calculate the sum of the three measurements. Give the answer to the correct number of significant figures.
12.52 meters meters meters = _______
Practice Problems
2. Perform each operation. Express your answers to the correct number of significant figures.
a meters meters meters = _______
b meters – 2.11 meters = _______
c meters meters = _______
d meters – 17.3 meters = _______
3. Find the total mass of three diamonds that have masses of 14.2 grams, 8.73 grams, and gram.

19. Sample Problem 3.3 Significant Figures in Multiplication and Division
1. Perform the following operations. Give the answers to the correct number of significant figures.
a meters x 0.34 meter = _______
b meters x 0.70 meter = _______
c meters / 8.4 = _______
Practice Problems
2. Solve each problem. Give the answers to the correct number of significant figures.
a. 8.3 meters x 2.22 meters = _______
b meters / 12.5 = _______
c seconds x 1 minute = _______ seconds
3. Now round each measurement from 2. to one significant figure. Write each of your answers in scientific notation.