SL: Metrics Lesson

Metrics

What is the difference between a gallon and a liter? An inch or a meter?

Did you know that Burma, Liberia, and the United States are the only 3 countries that have not adopted the International System of Measurement (SI System of Measurement)? Why do you think that is? Why should you study the SI System of Measurement if we do not use it in our everyday life?

At the end of this lesson, you should be able to answer these questions and understand why the International System of Measurement is essential to the scientific community.

Using the SI System of Measurement

Are you surprised that the countries in RED are the only ones that DO NOT USE the SI system of measurement?

Why Do We Need a System of Measurement?

Scientists need a common system of measurement so they can share and compare data. The Metric System (also known as the International System of Measurement, or "SI") has been around since 1790. Since that time, researchers have gladly embraced it when collecting data and performing experiments. What makes it so popular among scientists? To begin with, it is remarkably easy to use. The metric system is a decimal system of measurement whose units are based on multiples of 10.

Let's start by reviewing the basic units of metric measurement below. This table has been adapted from the US Metric Association (USMA):

Basic Units of Metric Measurement

Quantity Measured	Base Unit	Abbreviation	Tool Used
length/height	meter	m	meter stick, measuring tape
mass*	gram	g	balance or electronic scale
volume	liter	L	graduated cylinder, syringe, burette
time	second	s	stopwatch, clock
temperature	Celsius	C	thermometer
area	meters squared	m2	meter stick, measuring tape
cubic volume	centimeters cubed	cm3	graduated cylinder, syringe, burette

*mass is often confused with "weight"; mass is a measure of the amount of matter in an object whereas weight is the force of gravity on that object (Weight = Mass x Gravity)

What's an SI Prefix?

We can use the metric system to help us out! All measurements in the metric system are expressed as multiples of ten. If you can count to, multiply, and divide by 10, you can use this measurement system.

First, you need to know your SI prefixes. You would put one of these prefixes in front of a base unit (table above) to express that it is a division or multiple of that base number. Study the table below:

SI Prefixes

Prefix (symbol)	Factor of 10	Example: meter as base unit	Example: liter as basic unit	Example: gram as basic unit
kilo- (K)	1000 or thousand times the unit	Kilometer	Kiloliter	Kilogram
hecto- (h)	100 or hundred times the unit	hectometer	hectoliter	hectogram
deca- (da)	10 or ten times the unit	decameter	decaliter	decagram
UNIT (meter, liter, gram)	1	meter	Liter	gram
deci- (d)	0.1 or a tenth of the unit	decimeter	deciliter	decigram
centi- (c)	0.01 or a hundredth of the unit	centimeter	centiliter	centigram
milli- (m)	0.001 or a thousandth of the unity	millimeter	milliliter	milligram
micro- ($\mu$m)	0.000001 or a millionth of the unit	micrometer	microliter	microgram

So How Can We Convert?

Knowing how to convert between different metric amounts as we did in the example above, is an important science skill. Watch the tutorial below to learn how to do some metric conversion problems.

Metrics Challenge and Before You Go

Practice Time! Use the knowledge you learned from the lesson to complete the practice activities below.

Before You Go You Need To Know

The following key points are from the explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

1. Reasons why the International System of Measurement (SI) is important.

• Communication with people around the world; easy to convert because it uses a decimal-based system

2. What are the basic units of metric measurement and what do they measure?

• Meter (length); Mass (grams);
• Volume (liters); Time (seconds);
• Temperature (Celsius);
• Area (meters squared);
• Cubic Volume (centimeters cubed)

3. How to do metric conversion problems

• Example: 1 meter = 100 centimeters

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