1. How much? How long? How many?
Measurement
How much? How long? How many?

2. Exact and inexact numbers
A number with no uncertainty it
A dozen donuts, seven students, etc.
Inexact number:
A number that has a degree of uncertainty in it; results anytime a measurement is made
Height of student; temperature of student

3. Precision and Accuracy
How close a measured value is to the actual (true) value
Precision:
How close the measured values are to each other

4. Testing our knowledge How accurate? How Precise? Low accuracy
High precision

5. Testing our knowledge How accurate? How Precise? High accuracy
Low precision

6. Testing our knowledge How accurate? How Precise? High accuracy
High precision

7. Systems of Measurement
English:
Commonly used in commerce and homes
Inch, foot, pound, quart, and gallon
Metric system
Used worldwide
SI system
Revised in 1960 with improved units
SI stands for “French Systeme International d’Unites”
Used by scientists

8. SI System Meter m gram g Second s kelvin K mole ampere A candela cd
The Seven Base Units in the SI system:
Base quantity
Unit Name
Unit Abbreviation
Length
Meter m
Mass
gram g
Time
Second s
Temperature
kelvin K
Amount of substance
mole
Electric current
ampere A
Luminous intensity
candela cd

9. Metric system prefixes
Common prefixes
For example,
100 cm = 1 m
1,000 mg = 1 gm
Kilo k
1,000
Deci d
1/10
Centi c
1/100
Milli m
1/1,000

10. Length Meter is the SI base unit of length 1 meter=1.05 yards
A dime is about 1 mm thick
Or…1/1000 of a m
Your little finger is about 1 cm across
Or…1/100 of a m

11. Mass vs. Weight Mass Weight
A measure of the total quantity of matter in an object
Weight
A measure of the force exerted on an object by gravitational forces
If you weigh 60 kg on Earth, will you weigh more or less on the moon? Why?

12. Mass vs. Weight How much does this astronaut floating in space weigh?
What is the astronaut’s mass?

13. Mass Kilogram is the SI unit for mass
Note that the prefixes are added to gram not kilogram, i.e., centigram, milligram, etc.
10 pennies weigh about 1 gram
1 gram is 1/1,000 kilogram
Aspirin commonly is 325 mg
1 milligram = 1/1000 gram

14. Area and volume Area: measure of extent of a surface
For a square, length vs width
Square feet, ft2
Square cm, cm2
Volume: measure of the amount of space occupied by an object
For a cube, side x side x side
Cubic feet, ft3
Cubic cm, cm3

15. Volume Cubic meter (m3) is the SI system base unit for volume
A m3 is too large to be used in the chemistry lab, so cm3 is much more common
1 cubic cm (cm3 )= 1 milliliter (ml)
1 liter is a volume equivalent to that of a cube that is
10 cm x 10 cm x 10 cm or 1,000 cm3

16. SI Units
The best way to understand SI units is to use them in everyday life
Everyday examples

17. Measuring volume
Technique for measuring volume

18. Temperature A measure of the hotness or coldness of an object
Three scales:
Kelvin
after William Kelvin ( )
Does not use degree symbol
Celsius
After Anders Celsius ( )
Most commonly used in science

19. Three scales Kelvin Celsius Fahrenheit
after British mathematician and physicist, William Kelvin ( )
Does not use degree symbol
No negative numbers
Celsius
after Swedish astronomer, Anders Celsius ( )
Most commonly used in science
Fahrenheit
After German physicist, Gabriel Fahrenheit ( )
Based on the temperature of a salt-ice mixture as 0°F and the boiling point of mercury at 600°F

20. Common temperatures Freezing point of water Room temperature
0°C=32°F= K
Room temperature
22°C=72°F=295 K
Boiling point of water
100°C=212°F=373 K