Metric System

History

At the end of the 18th century in France, scientists created the metric system.

It was designed with several features in mind. 1. that each type of measurement (mass, volume, and

length) would only have one unit; for example, length would be measured in meters instead of in feet, inches, rods, ells, hands, or any other specialized measures that may or may not be easy to convert between

2. the metric system would be based on units of 10 for easy conversions

Who uses the Metric System?

SCIENTISTS (and science students) Almost every country EXCEPT the United States.

The US uses the English unit of measurement which is based on the lengths, weights, areas and volumes of everyday objects.

Using the same system of measurement gives scientists a common language.

In 1960 at the International Convention, the metric system was adopted as the “International system of Units” or SI.

SI is based on units of ten.

Length

The basic unit of length in the metric system is the meter (m)

The meter is = to 39.4 inches

Volume

Volume is the amount of space an object takes up.

The basic unit of volume is the liter (L) The liter is usually used for measuring the volume of

liquids The volume of solids can be measured in cubic centimeters (cc or cm3) = a cube that

measures 1cm x 1cm x 1cm 1cc is exactly equal to in volume to 1 ml

Mass

Mass is a measure of the amount of matter in an object

The basic unit of mass is the gram (g)

Weight

Weight is a measure of the attraction between two objects due to gravity

Your weight on another planet may differ due to the amount of gravity, however your mass will always be the same

Density

The relationship between mass and volume is called density

Density is defined as the mass per unit volume of a substance.

Density = Mass

Volume

Density Practice Problem

A carton of milk weighs 1000 grams and takes up 100cm3 of space, what is it’s density? DON’T FORGET YOUR UNITS!!

Density = Mass = 1000g = 10 g/cm3 Volume 100cm3

Temperature

In the metric system, temperature is measured on the Celsius scale.

On this temperature scale, water freezes at 0o C and boils at 100oC.

The metric system was set in such a way that there was exactly 100 degrees between freezing and boiling point of water.

Normal body temperature is 37oC. Room temperature is about 21oC.

Metric Prefixes used in Conversion

How can you remember this?

How do you convert from one unit to another? For every space that you move you move

the decimal one place to the left or the right

A Sample Problem…

3.45 Kg = _____g

1 2 3

3450.

Another Sample Problem

756 ml = ______L

123

.756

Dimensional Analysis

Dimensional Analysis is another way of converting units.

It is often used to convert units from

English to Metric or vise versa.

Your friend in England runs 3 kilometers a day while you run 3000 yards a day.

Using kilometers which of you runs a longer distance?

Steps for Dimensional Analysis

•Step 1: Determine the given unit and the desired unit.

Given: yards (3000)

Desired: kilometers

Step 2: Find the relationship between the units and consider the possible conversion factors

Known:

12 inches / 1 foot

1 yard / 3 feet

2.54 centimeters / 1 inch

100 centimeters / 1 meter

1000 meters / 1 kilometers

Step 3: Choose the conversion factor whose denominator has the same units as your given value to start with.

Start with 1 yard

3 feet

Step 4: Write the original value next to the conversion factor with a multiplication sign between them. Cancel like terms.

3000 yds x 3 ft x 12in x 2.54cm x 1m x 1km

1yd 1ft 1in 100cm 1000m

Step 5: Multiply the resulting equation.

3000 yds x 3 ft x 12in x 2.54cm x 1m x 1km

1yd 1ft 1in 100cm 1000m

1) Multiply across the top: 274,320

2) Multiply across the bottom: 100,000

3) Divide top by bottom: 2.7432 km

Solution to equation

3000 yards = 2.7432 km which is less than 3km. Therefore your friend in England runs more than you do per day.