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)

What would you use to measure the length of your arm? Liters 2.Meters 3.Grams 4.Grams/Milliliter 20

What would you use to measure how much sugar is in one teaspoon? Liters 2.Meters 3.Grams 4.Kilograms 20

What would you use to measure how much you weigh? Liters 2.Meters 3.Grams 4.Kilograms 20

What would you use to measure the width of the room? Liters 2.Meters 3.Grams 4.Grams/Milliliter 20

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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

What would you use to measure how much water is in a pool? Liters 2.Meters 3.Grams 4.Grams/Milliliter 20

More Derived Units 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

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 /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? m m m m 20

How many grams are 1.12kg? g g g g 20

How many Liters are 591mL? L L L L 20

What is 2.5cm in mm? mm 2..25mm 3.25mm mm 20

0.355L is how many mL? mL mL 3.355mL mL 20