Transcript The Metric System - De Soto Area School District

The Metric System
Seventh Grade
What is the metric
system?
 A common system of measurement used
throughout most of the world
 A decimal system based on powers of 10
 Scientists worldwide use the metric
system – it is precise
 AKA the International System of Units,
abbreviated SI
What is the metric
system?
 We use decimals to specify units of
measurement when we need more
precision
 For example, when specifying the height
of a person 1.63 meters tall, to say that
person is 1 or 2 meters tall doesn’t give
us a very good idea how tall that person
really is
Who invented it?
 It was first proposed in 1791
 The French were the first to adopt it
 The National Assembly of France first
declared the “new” measures to be the
legal measures in France in 1795
 Its use in France was made mandatory in
1837
Who uses it today?
 Most of the world
 All countries EXCEPT:
 Myanmar
 Liberia
 The United States
 All industrialized countries except the
U.S. uses the metric system
The metric system is
based on powers of 10
 Why? Seems to be a logical choice
 Many cultures have used 10 as the basis
for their number systems
 Probably because humans have 10
fingers and 10 toes
Basic Units
 Length - the meter
 Volume – the liter
 Mass – the gram
Prefixes:
 Metric units small than 1
have Latin Prefixes:
 Deci = tenth = .1
 Centi = hundredth = .01
 Milli = thousandth = .001
Prefixes:
 Metric units larger than 1 have Greek
prefixes:
 Deka = ten = 10
 hecto = hundred = 100
 Kilo = thousand = 1,000
Focus on length:
 Length = the distance between two fixed
points.
 The standard unit of length in the metric
system is the meter.
 A meter is a little longer than a yard.
The meter
 Scientists spent years carefully
measuring two points on Earth at sea
level
 They used these points to determine the
distance from the north pole to the
equator – ¼ the circumference of the
Earth
 They then divided that distance into 10
million parts – each part called a meter
Other units of length:
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Millimeter = mm = .001 meter
Centimeter = cm = .01 meter
Decimeter = dm = .1 meter
Meter = m = 1 meter
Dekameter = dk = 10 meters
Hectometer = hm = 100 meters
Kilometer = km = 1,000 meters
Focus on mass
 Mass = the amount of matter in an object
 The standard unit of mass in the metric
system is the kilogram
 A gram has about the same mass as a
paper clip
The gram
 Scientists tried to establish a unit that
would describe how much an object
weighs
 Because water is readily available all
over the world, they decided to call the
weight of one cubic centimeter of pure
water at a given temperature a gram
The gram
 However, weight is an intrinsically
unreliable measurement
 Weight is dependent on gravity
 A more reliable measurement is that of
mass – how much matter an object
contains
 The kilogram became the standard unit
of mass around the world
Other units of mass
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Milligram = mg = .001 gram
Centigram = cg = .01 gram
Decigram = dg = .1 gram
Gram = g = 1 gram
Kilogram = kg = 1,000 grams
Focus on volume
 Volume = the amount of space an object
takes up
 The standard unit of volume in the metric
system is the liter
 One liter is a little larger than a quart
Other units of volume:
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Milliliter = ml = .001 liter
Centiliter = cl = .01 liter
Deciliter = dl = .1 liter
Liter = L = 1 liter
Kiloliter = kl = 1,000 liters
Focus on time
 Time = interval or duration elapsing
between events
 The standard unit of time in the metric
system is the second
 Metric representation of second = s
Other units of time
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1 minute = 60 seconds
1 hour = 60 minutes = 3,600 seconds
1 day = 24 hours
1 week = 7 days
1 year = 365 ¼ days (amount of time it
takes the Earth to travel around the sun)
Other units of time
 In practice, every three calendar years
will have 365 days, and every fourth year
is a “leap year”, which has 366 days, to
make up for the extra quarter day over
four years. The years 2008, 2012, and
2016 will be leap years. This gives us a
total of 52 complete 7 day weeks in each
calendar year, with 1 day left over (or two
in a leap year).
Other units of time
 The year is divided into 12 months, each
of which has 30 or 31 days, except for
February, which has 28 days (or 29 days
in a leap year)!
Focus on temperature
 Temperature = the measure of hotness or
coldness
 The standard unit of temperature in the
metric system is degrees Celsius
 Metric representation of temperature = °C
Focus on temperature
 Temperature is expressed in degrees
Celsius in the metric system
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Water freezes at 0°C
Water boils at 100°C
A hot day is about 30°C
Normal body temperature is 37°C
Metric System vs. English
 1 meter = 1 yardstick plus the length of a
piece of chalk
 1 centimeter = the width of some part of
your smallest finger or fingernail
 1 kilometer = a little more than ½ a mile
 1 kilogram = about the mass of 2.2 lbs. of
butter
Metric System vs. English
 1 gram = about the mass of a large
thumbtack ( a nickel = about 5 grams)
 1 liter = 1 quart plus ¼ cup
 1 milliliter = 1/5 tsp. (1 tsp. = 5 ml)
The end…
 Happy metricating!