1. Chapter 2-2 Units of Measurement
Modification of Mrs. Rugh’s presentation 9/22/14

2. Measurements are information that represent quantities.
Measurement is different from Quantity

3. A quantity is something that has size, magnitude, or amount.
Measurements
A quantity is something that has size, magnitude, or amount.
Example: 1 teaspoon
Unit of measurement
Measurement
Quantity is volume

4. Measurement Standards
Le Systeme International d’Unites (SI)
Adopted in 1960 by the General Conference on Weights and Measures.
Now used and agreed upon by scientists around the world.
This is basically what we call the “metric” system

5. Not all units in this book are SI units
SI system
Has 7 “base units”
Most other units are derived from combinations of 2 or more “base units”
Not all units in this book are SI units

6. Measurement Standards
SI Units are defined in terms of standards of measurements.
In 1795 the meter was defined as one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level)
Before 1927 the official meter was defined by the length of a platinum-iridium bar kept in France.
Since 1983, the meter has been defined as "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second."[2]

7. Measurement Standards
Kilogram is the base unit of mass and is defined as being equal to the mass of the International Prototype of the Kilogram (IPK).
It is the only SI unit that is still defined by an artifact instead of a physical property.
However, there is discussion to define the kilogram in terms of a fundamental constant of nature.

8. Measurement Standards
The second is the base unit of time
Since 1967, the second has been defined to be:
the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.[

9. SI Base Units
Quantity Unit Unit Quantity symbol name abbreviation Length l meter m Mass m gram g Time t second s Temperature T kelvin K Amount of n mole mol substance You have a handout with this information on it…

10. Mass ≠ Weight
Mass is a measure of the amount of matter, weight depends on the local gravitational field.
We usually measure mass with a balance, weight is usually measured with a spring scale.
We will talk about MASS only in this class (leave weight for physics…

11. Prefixes –what do they MEAN
The handout has the important prefixes you need to know on it.
You should know the prefixes on the handout because you will use them…over and over…and over again.

12. Prefixes –what do they MEAN
Come up with one example of what you might measure with each of these units in meters.

13. Which unit (with appropriate prefix) would you use to measure this stuff?
Diameter of an atom
Weight of an elephant
Area of the Tacoma Dome
Temperature of the summit of Mt. Rainier
Temperature in outer space

14. Derived SI Units Derive v.
Mathematics: Obtain (a function or equation) from another by a sequence of logical steps, for example by differentiation: the volume fraction of the soil can then be derived as a function of L
Oxforddictionary.com

15. Length (m) x Length (m) = Area (m2)
Derived SI Units
derived units…units that are created by combining 2 or more SI Base Units (usually through multiplying or dividing base units).
For example:
Length (m) x Length (m) = Area (m2)
Mass (kg)/Volume (m3) = Density (kg/m3)

16. Example: Volume The amount of space occupied by an object. Solids:
m x m x m = m3
Liquids and gases: 1 Liter = 1 dm3 =
1000 cm3
So 1 mL = 1 cm3

17. The ratio of mass to volume, or mass divided by volume
Density
The ratio of mass to volume, or mass divided by volume
D = mass/volume or D = m/v
Often (though not always) expressed in units of g/cm3.

18. Quick Check Units of Measurement Quantity 5 ns Nanoseconds time
3.2 kg/L
Kg/L
density
0.88 pm
Picometers
length
540 km2
Square kilometers
area
173 K
Kelvin
temperature
2 mm3
Cubic millimeters
volume
6.02x1023 mol
moles
Amount of substance
5ns time
3.2 kg/L density
0.88 pm length
540 km2 area
173 K temperature
2 mm3 volume
23degC temperature

19. Now Do the Practice Problems Due tomorrow if you don’t finish in class…