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The Metric System
Objectives:
1. Explain why scientists use a standard
measurement system.
2. Identify SI units of measure for length, mass,
volume, and density
3. Calculate volume and density
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The metric system is a system of measurement
based on the number ten.
Modern scientist use a version of the metric system
called the international system of units abbreviated
as SI.
Scientists all over the world use SI units to measure
length, volume, mass, density, temperature and
time
Using SI as the standard system of measurement
allows scientists to compare data and
communicate with each other about their results.
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The basic unit of length in the SI system is the
meter.
One meter is about the distance from the floor to a
doorknob.
To measure objects smaller than a meter, scientists
use the centimeter or millimeter.
One meter is equal to 100 centimeters or 1000
millimeters.
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Mass is the measure of the amount of matter an
object contains.
The basic unit of mass in the SI system is the
kilogram.
The mass of a wooden baseball bat is about 1
kilogram.
To measure the mass of smaller objects, you can
use the gram or milligram.
One kilogram is equal to 1000 grams.
A very common tool to measure mass is the triplebeam balance.
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Volume is the amount of space an object takes up.
The basic unit of volume in SI is known as the liter
(L)
One liter is equal to 1000 mL
Scientists commonly use a graduated cylinder to
measure liquid volumes.
The liquid at the top of a graduated cylinder will be
curved. This curve is called a meniscus.
One cubic centimeter is exactly equal to one
millilter.
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The volume of a regular shaped solid can be found
using this formula: Length x Width x Height.
To measure the volume of an irregular solid, you
record the volume of water in a graduated cylinder.
Then, carefully place the irregular solid into the
water. Record the volume of the water with the
object in the water.
Subtract the volume of water alone from the
volume of the water and the object.
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Density is the measure of how much mass is
contained in a given volume.
The formula to solve for density is:
Density = Mass/Volume
Because density is actually made up of two
measurements; mass and volume an object’s
density is expressed as a combination of two units.
Two common density units are grams per cubic
centimeter and grams per milliliter.
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The density of a substance is the same for all
samples of that substance.
For example, all samples of pure gold no matter
how large or small have a density of 19.3 g/cm3
An object will float if it is less dense than the
surrounding liquid.
For example, the density of water is 1 g/cm3. A
piece of wood with a density of 0.8 g/cm3 will float
in water.
Substance
Density (g/cm3)
Air
0.001
Ice
0.9
Water
1.0
Aluminum
2.7