Metric System

Friday, April 21, 2023

SI Units

Notes= Green

The basics

What is SI? SI stands for “Le Système international

d'unités” or The International System of Units. SI units are used throughout the world except

in the United States and some of the United Kingdom.

What are the SI units?

There are 5 major types of measurements: Length Mass Volume Temperature Time

What are the units?!

Length: Length is measured in METERS Mass: Mass is measured in GRAMS Volume: Volume is measured in LITERS Temperature: Temperature is measured in

Degrees Celsius

SI vs English

The “English” system is what we are probably more familiar with. English units for the same measures are: Length: inches/feet/yards/miles Mass: ounces/pounds/tons Volume: fluid ounce/cups/quarts/gallons Temperature: Fahrenheit/Celsius Time: Second

Why use SI?

There is one key advantage of SI over English. Metric (SI) units work in 10s, therefore it is

very easy to convert from big units to small units and vice versa.

English units are not easy to convert. Can you easily convert one mile to inches?

Moving between units

To change from one unit size or type to another is called a “conversion”.

To help us learn conversions you will want to familiarize yourself with this saying:

“King Henry Died (Monday) drinking chocolate milk”

Or Kinky Haired Ducks (Under) Dads Car Motor

Say What?

King: Kilo (meaning 1000) Henry: Hecto (meaning 100) Died: Deca (meaning 10) Monday : the base unit (1) (Meters) drinking: deci (meaning 1/10) chocolate: centi (meaning 1/100) milk: milli (meaning 1/1000)

Or What?

Kinky: Kilo (meaning 1000) Haired: Hecto (meaning 100) Ducks: Deca (meaning 10) Under : the base Unit (1) Dads: deci (meaning 1/10) Car: centi (meaning 1/100) Motor: milli (meaning 1/1000)

And their symbols/abbreviations…

Name kilo- hecto- deca- No Prefix, unit only

Symbol k h da None

Factor 103 102 101 100

Name deci- centi- milli-

Symbol d c m

Factor 10-1 10-2 10-3

Life examples

Create this chart in your notebook to take up a ½ page.

Kilo-

(k)

(base) milli-

(m)

Gram

(g)

Liter

(L)

Meter

(m)

Fill it out!

Take the next 10 minutes to think of items you could measure using each box! Helpful starters:

1 gram= 1 paperclip 1 liter= 1 bottle of water 1 meter= 1 meter stick

Basics

Metric System

The metric system is based on a base unit that corresponds to a certain kind of measurement

Length = meter Volume = liter Weight (Mass) = gram

Metric System

Prefixes plus base units make up the metric system Example:

Centi + meter = Centimeter Kilo + liter = Kiloliter

Metric System The three prefixes that we will use the

most are: kilo centi milli

kilo hecto deca

Base Units

meter

gram

liter

deci centi milli

Metric System So if you needed to measure length you

would choose meter as your base unit Length of a tree branch

1.5 meters Length of a room

5 meters Length of a ball of twine stretched out

25 meters

Metric System But what if you need to measure a longer

distance, like from your house to school? Let’s say you live approximately 10 miles from

school 10 miles = 16093 meters

16093 is a big number, but what if you could add a prefix onto the base unit to make it easier to manage:

16093 meters = 16.093 kilometers (or 16.1 if rounded to 1 decimal place)

Metric System These prefixes are based on powers of 10. What

does this mean? From each prefix every “step” is either:

10 times larger or

10 times smaller

For example Centimeters are 10 times larger than millimeters 1 centimeter = 10 millimeters

kilo hecto deca

Base Units

meter

gram

liter

deci centi milli

Metric System

Centimeters are 10 times larger than millimeters so it takes more millimeters for the same length

1 centimeter = 10 millimeters

Example not to scale

1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm

1 cm

40

41

41

40 40

Metric System For each “step” to right,

you are multiplying by 10

For example, let’s go from a base unit to centi

1 liter = 10 deciliters = 100 centiliters

2 grams = 20 decigrams = 200 centigrams

kilo hecto deca

meter

liter

gram

deci centi milli

( 1 x 10 = 10) = (10 x 10 = 100)

(2 x 10 = 20) = (20 x 10 = 200)

Metric System An easy way to move within the metric system is by

moving the decimal point one place for each “step” desired

Example: change meters to centimeters

1 meter = 10 decimeters = 100 centimeters

or

1.00 meter = 10.0 decimeters = 100. centimeters

kilo hecto deca

meter

liter

gram

deci centi milli

Metric System Now let’s try our previous example from meters to

kilometers:

16093 meters = 1609.3 decameters = 160.93 hectometers = 16.093 kilometers

So for every “step” from the base unit to kilo, we moved the decimal 1 place to the left (the same direction as in the diagram below)

kilo hecto deca

meter

liter

gram

deci centi milli

Metric System If you move to the left in the diagram, move the

decimal to the left

If you move to the right in the diagram, move the decimal to the right

kilo hecto deca

meter

liter

gram

deci centi milli

Metric System Now let’s start from centimeters and convert to kilometers

400000 centimeters = 4 kilometers

400000 centimeters = 4.00000 kilometers

kilo hecto deca

meter

liter

gram

deci centi milli

Metric System Now let’s start from meters and convert to kilometers

4000 meters = 4 kilometers

kilo hecto deca

meter

liter

gram

deci centi milli

kilo hecto deca

meter

liter

gram

deci centi milli

• Now let’s start from centimeters and convert to meters

4000 centimeters = 40 meters

Metric System Now let’s start from meters and convert to centimeters

5 meters = 500 centimeters

kilo hecto deca

meter

liter

gram

deci centi milli

kilo hecto deca

meter

liter

gram

deci centi milli

• Now let’s start from kilometers and convert to meters

.3 kilometers = 300 meters

Metric System Now let’s start from kilometers and convert to

millimeters

4 kilometers = 4000000 millimetersor

4 kilometers = 40 hectometers = 400 decameters = 4000 meters = 40000 decimeters = 400000 centimeters = 4000000 millimeters

kilo hecto deca

meter

liter

gram

deci centi milli

Metric AbbreviationsUnit Abbreviation Number

kilo k 1,000

hecto h 100

deka/deca da 10

Single None 1

deci d 0.1

centi c 0.01

milli m 0.001

Metric System Summary

Base units in the metric system are meter, liter, gram

Metric system is based on powers of 10 For conversions within the metric system, each

“step” is 1 decimal place to the right or left Using the diagram below, converting to the right,

moves the decimal to the right and vice versa

kilo hecto deca

meter

liter

gram

deci centi milli