1. Section 2 Units of Measurement
Chapter 2
Objectives- after viewing this lesson you should be able to do the following:
Distinguish between a quantity, a unit, and a measurement standard.
Name and use SI base units.
Name and use SI derived units.
Name and use metric prefixes.
Perform metric conversions.

2. Objectives Distinguish between mass and weight.
Perform density calculations.
Transform a statement of equality into a conversion factor.
Use factor-label method, aka dimensional analysis, to solve problems.

3. Chapter 2 Units of Measurement Measurements represent quantities.
Section 2 Units of Measurement
Chapter 2
Units of Measurement
Measurements represent quantities.
A quantity is something that has magnitude, size, or amount.
the liter is a unit of measurement used to represent volume
volume is a quantity
The choice of unit depends on the quantity being measured.

4. Chapter 2 SI Measurement
Section 2 Units of Measurement
Chapter 2
SI Measurement
Scientists all over the world have agreed on a single measurement system called Le Système International d’Unités, abbreviated SI.
SI has seven base units
most other units are derived from these seven
A base unit is independent of other units
A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world.

5. SI (Le Systéme International d´Unités)
Visual Concepts
Chapter 2
SI (Le Systéme International d´Unités)

6. Section 2 Units of Measurement
Chapter 2
SI Base Units

7. Chapter 2 SI Base Units Mass
Section 2 Units of Measurement
Chapter 2
SI Base Units
Mass
Mass is a measure of the quantity or amount of matter contained in an object.
Weight is a measure of the gravitational pull on a mass.
Weight does not equal mass.

8. Chapter 2 SI Base Units Length, Temperature, Amt. of Substance
Section 2 Units of Measurement
Chapter 2
SI Base Units
Length, Temperature, Amt. of Substance
Length is a measure of distance.
Temperature is a measure of the average kinetic energy in a sample of matter.
( KE=1/2m . V2 )
The Amount of Substance measures the total number of individual particles of matter contained in a sample of matter.
( Avagadro’s # = 1 mole= 6.02 x 1023 )

9. Chapter 2 Derived SI Units
Section 2 Units of Measurement
Chapter 2
Derived SI Units
Combinations of SI base units form derived units.
pressure is measured in kg/m•s2, or pascals
pressure is force per unit area

10. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Volume
Volume is the amount of space occupied by an object.
The derived SI unit is cubic meters, m3
The cubic centimeter, cm3, is often used
The liter, L, is a non-SI unit
1 L = 1000 cm3
1 mL = 1 cm3

11. Visual Concepts
Chapter 2
Volume

12. Measuring the Volume of Liquids
Visual Concepts
Chapter 2
Measuring the Volume of Liquids

13. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Force is a mass accelerating .
The derived SI unit is the Newton , N,, kgm/s2
Velocity is distance covered per unit time, m/s
Acceleration is a change in velocity over time, m/s2

14. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Energy is applied force through a distance.
The derived SI unit is the Joule , J, kgm2/s2
Concentration is amount of substance per unit volume, mol/m3

15. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Density
Density is the ratio of mass to volume, or mass divided by volume.
The derived SI unit is kilograms per cubic meter, kg/m3
g/cm3 or g/mL are also used
Density is a characteristic physical property of a substance.

16. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Density
Density can be used as one property to help identify a substance

17. Visual Concepts
Chapter 2
Equation for Density

18. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Sample Problem A
A sample of aluminum metal has a mass of
8.4 g. The volume of the sample is 3.1 cm3. Calculate the density of aluminum.

19. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Sample Problem A Solution
Given: mass (m) = 8.4 g
volume (V) = 3.1 cm3
Unknown: density (D)
Solution:

20. Chapter 2 Conversion Factors
Section 2 Units of Measurement
Chapter 2
Conversion Factors
A conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other.
example: How quarters and dollars are related

21. Visual Concepts
Chapter 2
Conversion Factor

22. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Dimensional analysis is a mathematical technique that allows you to use units to solve problems involving measurements.
quantity sought = quantity given × conversion factor
example: the number of quarters in 12 dollars
number of quarters = 12 dollars × conversion factor

23. Using Conversion Factors
Section 2 Units of Measurement
Chapter 2
Using Conversion Factors

24. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Deriving Conversion Factors
You can derive conversion factors if you know the relationship between the unit you have and the unit you want.
example: conversion factors for meters and decimeters

25. Chapter 2
Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.

27. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Sample Problem B
Express a mass of grams in milligrams and in kilograms.
Keep in mind that all “base” units such as the gram in this example are what the metric prefixes are affixed to in order to change the value on the unit.
For conversion purposes all of these “base “ units are assigned a value of (100=1)

28. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Sample Problem B Solution
Express a mass of grams in milligrams and in kilograms.
Given: g
Unknown: mass in mg and kg
Solution: mg
1 g = 1000 mg
Possible conversion factors:

29. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Sample Problem B Solution, continued
Express a mass of grams in milligrams and in kilograms.
Given: g
Unknown: mass in mg and kg
Solution: kg
1 000 g = 1 kg
Possible conversion factors:

30. Chapter 2 Multiple Choice
Standardized Test Preparation
Chapter 2
Multiple Choice
8. A measurement of mg converted to grams equals
A g.
B g.
C g.
D g.

31. Chapter 2 Multiple Choice
Standardized Test Preparation
Chapter 2
Multiple Choice
8. A measurement of mg converted to grams equals
A g.
B g.
C g.
D g.