The SI System

or

How to Know “How Much?”

The Metric System

• Officially called the SI System• Based on increments of 10 (one decimal place or

zero)• A good measurement has a number and a unit• Prefixes on the unit name tell you how many zeroes to

put before or after a number• Used in every country around the world except the

USA and Báhrain• The official measurement system of the USA

since the late 1800s

Why you don’t already know the Metric System

Your parents didn’t know it

No incentive for companies to switch

You are still being taught the Imperial

System through everyday experiences

- Recipes

- Consumer goods

There is a slow, steady inclusion process

Base Units

• Base units are defined by only one measurement

Length

• Distance from one point to another• Meters (m) are the base units (a little longer

than a yard)

• For smaller items, centimeters (about one knuckle), and millimeters (the thickness of a dime) are used

Mass

• Amount of substance (number of particles) in an object

• Gram (g) is the base unit• It is too small for some common measurements

(about 1 paper clip of matter)

• Usually use the kilogram (kg) for basis of comparisons

• A kilogram is a little more than 2 pounds

Time

• How long it takes for something to happen• Also called “Time Elapsed” or “Elapsed Time”

• Seconds (s) are the base unit• Can lead to large numbers (1hr = 3600s)

Derived Units of the SI System

• Derived units are defined by two or more measurements • Volume

• Amount of space taken up by a substance

• Liters (L) are the base units (a little more than a quart)

• Liters are too large for some measurements, so milliliters (mL) are often used

The other derived unit

• Density• Amount of matter in an object divided by the space

taken up by the object

• “How much stuff is in how much space”

• Usually expressed in grams per milliliter (g/mL) for smaller amounts

• Expressed in kilograms per liter (kg/L) for larger amounts

• THE NUMBER DOES NOT CHANGE

What would you use to measure the length of your arm?

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1. Liters

2. Meters

3. Grams

4. Grams/Milliliter

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What would you use to measure how much water is in a pool?

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1. Liters

2. Meters

3. Grams

4. Grams/Milliliter

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What would you use to measure how much sugar is in one teaspoon?

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1. Liters

2. Meters

3. Grams

4. Kilograms

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What would you use to measure how much you weigh?

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1. Liters

2. Meters

3. Grams

4. Kilograms

20

What would you use to measure the width of the room?

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1. Liters

2. Meters

3. Grams

4. Grams/Milliliter

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Participant Scores500 Greg Bowman

500 Kevin Burkhart

500 Daniel Clink

500 Saadia Gauthier

500 Jeff Greene

500 Ashley Hayes

500 Kendra Hutchinson

500 Brian Jones

500 Julian Kilner

500 Brandon McDonald

SI Prefixes

• Used to show a number of base units• Think of them as coefficients (multipliers)• Easy to convert by sliding the decimal

SI Prefixes

• From the largest to the smallest• kilo- hecto- deka- BASE deci- centi- milli-• 1000 100 10 1 1/10 1/100 1/1000• “King Henry died by drinking chocolate milk.”• Put your finger on the unit you have, move it to

the unit you want• Move your decimal the same number of places in

the same direction that your finger moved

Testing your knowledge…

• Answer the five questions…• Use the “Metric Ruler” to slide the decimal

to get the desired units…• Ready?

What is 25mm in m?

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1. 2.5m

2. 0.25m

3. 0.025m

4. 0.0025m

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How many grams are 1.12kg?

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1. 112g

2. 0.00112g

3. 0.112g

4. 1120g

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How many Liters are 591mL?

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1. 0.591L

2. 59.1L

3. 0.059L

4. 5.91L

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What is 2.5cm in mm?

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1. 250mm

2. .25mm

3. 25mm

4. 0.025mm

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0.355L is how many mL?

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1. 3.55mL

2. 35.5mL

3. 355mL

4. 3550mL

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Participant Scores1000 Greg Bowman

1000 Daniel Clink

1000 Jeff Greene

1000 Kendra Hutchinson

1000 Brian Jones

1000 Julian Kilner

1000 Brandon McDonald

1000 Trevor Readdick

1000 Chelsea Vachon

900 Kevin Burkhart