Introduction to the Metric System

History

Created during French Revolution in 1790 French King overthrown 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 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

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

Universal - used everywhere by all scientists to communicate by all industrialized nations

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

Advantages of Using the Metric System

Advantages of Using the Metric System

Simple to use A few base units make up all

measurements length - meter mass - grams volume - liters temperature – degrees Celsius time - seconds

Advantages of Using the Metric System

There is only one 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

Length - the distance between two pointsstandard unit is meter (m) long distances are measured in km

1km = 1000m, 1 m = 1/1000th kmSmall distances measured in cm or mm

1 m = 100 cm , 1 cm = 1/100th m1 m = 1000 mm, 1 mm = 1/1000th m10 mm = 1 cm

Measured using a meter stick or ruler

Units of Measurement

Units of Measurement

Mass - the quantity of matter in an objectstandard unit is gram (g)

Measured using a digital scale or triple beam balance

Units of Measurement

Volume - the amount of space occupied by an objectstandard unit is liter (L)1 L = 1000 ml = 1000 cm3 = 1 dm3Measured using a graduated cylinder

Units of Measurement

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.

Units of Measurement

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

Units of Measurement

Timemetric unit is second (s)

Units of Measurement

Temperature - the degree of “hotness” of an object standard unit is

celsius (°C) But scientists generally

use the Kelvin Scale. Based on absolute zero.

measured with a thermometer

Temperature Conversions

Conversion Between Fahrenheit, Celsius, and Kelvin

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

Conversion and the Metric System

Measurement Unit Conversion

You can convert between units of measurementwithin the metric systembetween 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.

Unit Conversion Rules

Start with the given information… Then set up your unit factor… See that the original unit cancels out… Then multiply and divide all numbers…