1. Standards of Measurement
The International System of Units
(SI)

2. Units and Standards
In order for a measurement to be useful, a measurement standard must be used.
A standard is an exact quantity that people agree to use for comparison.

3. Measurement Systems
Suppose the length of a string in a ball of yarn is Can you tell how much string is in the ball?
NO!!
It could be 150 feet, 150 meters, or some unit you’ve never heard of.
In order for a measurement to make sense it must have a number and a unit.

4. International System of Units
In the U.S. we buy milk by the gallon, potatoes by the pound, and lumber by the foot.
These are a part of the English system of measurement.
Most other nations use a system of measurement based on multiples of ten.
This is known as the International System of Units or SI.

5. Common SI Prefixes Kilo- k 1000 Deci- d 0.1 Centi- c 0.01 Milli- m
Symbol
Multiplying Factor
Kilo- k
1000
Deci- d
0.1
Centi- c
0.01
Milli- m
0.001
Micro-
Nano- n

6. Using SI Units
Every type of quantity measured in SI has a base unit and a symbol for that unit.

7. SI Base Units Quantity Measured Unit Symbol Length Meter m Mass
Kilogram kg
Time
Second s
Electric current
Ampere A
Temperature
Kelvin K
Amount of substance
Mole
mol
Intensity of light
Candela cd

8. Length The SI base unit for length is the meter (m).
Remember: SI is based on powers of ten
Therefore:
1m=10dm=100cm=1000mm
Metric rulers and meter sticks are used to measure length.

9. 10 football fields= 1 kilometer
Choosing a Unit
The size of the unit you use to measure with will depend on the size of the item being measured.
1 centimeter
1 meter
10 football fields= 1 kilometer

10. Volume The amount of space occupied by an object.
Volume= length x width x height
V= 3cm x 3cm x3cm
V= 27cm
3 cm
3cm
3 cm 3

11. Mass Measurement of the matter in an object. Base unit: kilograms (kg)
Grams (g) and milligrams (mg) are used for measuring objects of small mass.
Which ball has more mass?
How many grams are in one kilogram?

12. Density
Density is the mass per unit of volume of a material. (Expressed as grams per cubic cm)
D=m/v
A cube of silver would be more dense than a cube of aluminum, even if they were the same size!!

13. That is -273 degrees Celsius, which is 273 degrees below freezing!!
Time and Temperature
The SI unit for time is the second (s).
The SI unit for temperature is the Kelvin (K).
0 degrees K is the COLDEST possible temperature, also known as absolute zero.
That is -273 degrees Celsius, which is 273 degrees below freezing!!

14. Summary
A standard is an exact quantity that people agree to use for comparison.
In order for a measurement to make sense it must have a number and a unit.
The International System of Units or SI is a system of measurement based on units of 10 and used by most nations around the world.
Every type of quantity measured in SI has a base unit and a symbol for that unit.
The SI base unit for length is the meter (m).
The size of the unit you use to measure with will depend on the size of the item being measured.
Volume= length x width x height
Mass is the measurement of the matter in an object (kg).
Density is the mass per unit of volume of a material. (Expressed as grams per cubic cm)
The SI unit for time is the second (s).
The SI unit for temperature is the Kelvin (K).