1. UNITS OF MEASUREMENT
The metric system

2. WHAT ARE UNITS OF MEASUREMENT?
Units describe what aspect of matter is being measured
Qualitative: something that is described
Using the senses
Quantitative: something that is measured
Examples:
Unit of distance – mile
Unit of volume – gallon
Unit of time – hour
Unit of weight - pound

3. SI UNITS OF MEASUREMENT
SI – Standards International
Set of units that are recognized by the scientific community
In science (unlike math), you need a unit for EVERY NUMBER
These are the units we will be using in this class – not English units

4. THE SI UNITS (THE METRIC SYSTEM)
Metric system is a base 10 system
To convert from one unit to another, you just move the decimal left or right
These are the most commonly used in this class
Distance – meter (m)
Mass – gram (g)
Volume – liter (L)
Time – second (s)
Temperature – degrees Celsius (°C)
Energy – Joules (J)

5. METRIC PREFIXES Prefixes modify the base unit
Gram, Liter, meter, etc.
You can put a prefix in front of any base unit and multiply the number:
kg is a kilogram: this means 1000 x grams
km is a kilometer: this means 1000 x meters
kL is a kiloliter: this means 1000 x liters

6. MASS – A QUICK EXPLANATION
Mass and weight are different
Weight can change. It is not an absolute value
Weight depends upon the force of gravity
You weigh more on Earth than on the Moon
Mass cannot change. It is an absolute value
Mass depends on the amount of matter in a substance
Mass does not change with gravity

7. METRIC CONVERSIONS – Copy for your notes
Giga G 109
Mega M 106
Kilo k 103
Hecto h 102
Deka dK 101
Base unit 100
Deci d 10-1
Centi c 10-2
Milli m 10-3
Micro u 10-6
Nano n 10-9
Pico p 10-12

8. STEPS TO CONVERT : EXAMPLE: 100mm = _?_cm
Find the meaning of all the prefixes in a conversion and look at the exponents
100mm = _____ cm
m (milli) = 10-3
c (centi) = 10-2
Find the difference in the exponents
(-3) – (-2) = 1

9. STEPS TO CONVERT
This is the number of spaces you are going to be moving the decimal
To figure out the direction, look at the units
If you go from smaller unit to bigger, move the decimal to the left
If you go from bigger unit to smaller, mover the decimal to the right

10. STEPS TO CONVERT
In the example, we are going from mm to cm
mm is smaller than cm, therefore we move the decimal to the left
100. mm  move decimal one space to the left
100mm = 10.0cm
Important note: Always use the exponents, don’t just count the spaces.

11. PRACTICE Try the following 3 conversions IN YOUR NOTES:
1500 g = __?__ kg
63.3 hL = __?__ cL
122,000 nm = __?__ cm

12. ANSWERS
1.500 g
633,000 cL mm