Introduction to the Metric System

Measurement by design

History

Created during French Revolution› in 1790‘s› 1793 French King Louis XVI beheaded› National Assembly of France sets up new

government › French Academy of Science told to design

new system of weights and measures › Lavaiosie appointed to head committee

History

Called Systeme International d’Unitès, › or SI - International System of Units

Revised periodically › by International Bureau of Weight and

Measures

Customary Units of Measurement

The English or Imperial System› a collection of functionally unrelated units

Difficult to convert from one unit to another Ex. 1 ft = 12 inches = 0.33 yard = 1/5280 miles

Typical Units › length - inch, foot, yard, mile › weight/mass - ounce, pound › volume - teaspoon, cup, quart, gallon › temperature - degrees Fahrenheit › time - minutes, hours

Advantages of Using the Metric System

Universal - Used all around the world › Used in the scientific community and is

the only accepted form of measurement › Used by the Olympics and International

Sporting events.› Used by all industrialized nations

except United States U.S. loses billions of dollars in trade

Advantages of Using the Metric System

Simple to use › A few base units make up all

measurements length - metre mass - grams volume - litres temperature – degrees Celsius time - seconds

Advantages of Using the Metric System

There is one standard unit of measurement for each type of quantity

› To simplify things, very small and very large numbers are expressed as multiples of the base unit. Prefixes are used to represent how much smaller or

larger the quantity is compared to the base unit.

Easy to convert from one unit to another › shift decimal point right › shift decimal point left

Advantages of Using the Metric System

Same set of prefixes for all units› Greek - multiples of the base

kilo - 1000 × the base hecto - 100 × the base deka - 10 × the base

› Latin - fractions of the base deci - tenths of the base centi - hundredths of the base milli - thousandths of the base

Mnemonic: “Kids Have Dropped Over Dead Converting Metrics.”

Metric Prefixes

Units of Length

Length - the distance between two points› standard unit is metre (m)› long distances are measured in km

Measured using a metre stick or ruler

Prefixes and Units of Length

centimetre - cm› 1 m = 100 cm› 1 cm = 1/100th m

millimetr e- mm› 1 m = 1000 mm› 1 mm = 1/1000th m› 10 mm = 1 cm› measures very small lengths

kilometre - km› 1 km = 1000 m› 1 m = 1/1000th km› measures long distances

Measuring Mass

Mass - the quantity of matter in an object› standard unit is gram (g)

Measured using a digital scale or triple beam balance

Measuring Volume and Capacity

Volume - the amount of space occupied by an object› standard unit is litre (L)› 1 L = 1000 ml = 1000 cm3 = 1 dm3› Measured using a graduated cylinder

Capacity - a measure of the volume inside a container

Prefixes and Units of Volume› Litre - L

1 L = 1000 milliliters 1 L = 1000 cubic centimeters = 1000 cm3

› millilitre - mL measures small volumes 1 mL = 1 cubic centimeter 1000 mL = 1 Liter 1 mL = 1/1000th liter

› kilolitre - kL measures large volumes 1 kL = 1000 LThe SI unit for volume is NOT the litre, it is a Cubic metre.

Litre are accepted as an SI derived unit.

Measuring Volume

Measured with a graduated cylinder› Determine value of each

mark on the scale› Read scale using the

lowest position of the meniscus Measure the meniscus at

eye level from the center of the meniscus.

In the case of water and most liquids, the meniscus is concave. Mercury produces a convex meniscus.

Displacement

Displacement› Amount of water an object replaces› Equal to its volume

Volume of a Solid, Irregular Object

Displacement - amount of water an object replaces› Procedure

Place graduate beaker beneath spout

Fill the overflow can with water until water begins to spill

Empty the excess water Place object to be measured

into the overflow can Remove when water stops

flowing out of the can Measure the displaced water

using a graduated cylinder.

Volume of a Solid, Irregular Object

Displacement Calculate the

difference between the initial and final volume measurement.

Volume of a Solid, Regular Object

Volume - length x width x height› V = 2.8 cm x 3.2 cm x 2.5 cm› V = 22.4 cm3› Measured with a ruler

Calculating Density

Density - a specific property of matter that is related to its mass divided by the volume. › D=M/V› the ratio of mass to volume

used to characterize a substance

› each substance has a unique density Units for density include:

g/mL g/cm3 g/cc

Measuring Time

Time› metric unit is second (s)

Measuring Temperature Temperature

- the degree of “hotness” of an object› standard

unit is celsius (°C)

› measured with a thermometer

Temperature Conversions

Conversion Between Fahrenheit, Celsius, and Kelvin

Example:› Convert 75 ºC to ºF› Convert -10 ºF to ºC

Measurement Unit Conversion

You can convert between units of measurement› within the metric system› between the English system and metric

system

Conversion and the Metric System

Measurement Unit Conversion

You can convert between units of measurement› within the metric system› between the English system and metric

system

Unit Conversion

Let your units do the work for you by simply memorizing connections between units.› Example: How many

donuts are in one dozen?› We say: “Twelve donuts in

a dozen.”› Or: 12 donuts = 1 dozen

donuts› What does any number

divided by itself equal?› ONE!

Unit Conversion

This fraction is called a unit factor› Multiplication by a unit

factor does not change the amount - only the unit.

› Example: How many donuts are in 3.5 dozen? You can probably do this in

your head but try it using the Factor-Label Method.

Dimensional Analysis : The Rules of Unit Conversion. Start with the given information… Then set up your unit factor… See that the original unit cancels

out… Then multiply and divide all

numbers…

Unit Conversion Practice

Example: Convert 12 gallons to units of quarts.

Unit Conversion Practice

Example: Convert 4 ounces to kilograms.