Metric System
Scientific
Measurements
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Metric System
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Developed by the French in the late 1700’s.
Based on powers of ten, so it is very easy to
use.
Used by almost every country in the world,
with the notable exception of the USA.
Especially used by scientists.
Abbreviated SI, which is French for Systeme
International.
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Metric Prefixes
Regardless of the unit, the entire
metric system uses the same prefixes.
 Common prefixes are:
kilo = 1000
centi = 1/100th
milli = 1/1000th
1 meter = 100 centimeters= 1000
millimeters
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Length
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Length is the
distance between
two points.
The SI base unit
for length is the
meter.
We use rulers or
meter sticks to
find the length of
objects.
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Mass
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Mass is the amount of matter that
makes up an object.
A golf ball and a ping pong ball are
the same size, but the golf ball has a
lot more matter in it. So the golf
ball will have more mass.
The SI unit for mass is the gram.
A paper clip has a mass of about one
gram.
The mass of an object will not change
unless we add or subtract matter
from it.
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Measuring Mass
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We will use a triple beam balance scale to
measure mass.
Gravity pulls equally on both sides of a
balance scale, so you will get the same
mass no matter what planet you are on.
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Weight
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Weight is a measure of the force of
gravity on an object.
Your weight can change depending on
the force of gravity. The gravity will
change depending on the planet you are
on.
The SI unit for weight is the Newton
(N).
The English unit for weight is the pound.
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Gravity
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Gravity is the force of attraction
between any two objects with mass.
The force depends on two things:
more distance = less gravity = less
weight
less distance = more gravity = more
weight
more mass = more gravity = more weight
less mass = less gravity = less weight
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Weight and Mass
Jill
Earth
1 gravity
Jupiter
2.5
gravities
30kg
On orbit
0 gravity
30kg
Moon
1/6th
gravity
30kg
mass
weight
300N
50N
750N
0 Newtons
30kg
Notice that Jill’s mass never changes.
Her mother will not allow us to take
parts off her, or add parts to her, so
her mass stays the same. Jill is 30kg of
little girl no matter where she goes!
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Volume
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Volume is the amount
of space contained in
an object.
We can find the
volume of box shapes
by the formula Volume
= length x width x
height
In this case the units
would be cubic
centimeters (cm3).
So a box 2 cm x 3 cm
x 5cm would have a
3
volume of 30 cmcopyright
cmassengale
V = L x W x H
Base Units
The base unit
for volume is
the Liter.
 We measure
volume with a
graduated
cylinder.
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Graduated Cylinders
Liquids form curved,
upper surfaces when
poured into
graduated cylinders
 To correctly read
the volume, read
the bottom of the
curve called the
meniscus
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Liquid Volume
When the metric system was
created, they decided that 1 cm3
of water would equal 1 milliliter of
water and the 1 mL of water will
have a mass of one gram.
 1cm3 water =1 ml of water = 1 gram
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Water Displacement
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We can use water
displacement to find
the volume of objects
that are not boxed
shaped.
We can put water in a
graduated cylinder. If
a rock causes the level
to rise from 7 to 9 ml,
the the rock must have
a volume of 2-mL.
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Water Mass and Volume
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1 cm3 water = 1 mL of water = 1
gram
So what would be the mass of 50 mL of
water be?
50 grams
So what would be the mass of 1 liter of
water be?
1 L = 1000 mL so its mass would be
1000 grams or a kilogram.
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Density
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Density is the amount of matter (mass)
compared to the amount of space (volume)
the object occupies.
We will measure mass in grams and
volume in ml or cm3
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Density Formula
Density is mass divided by volume.
 Density = mass/volume
 Remember, all fractions are division
problems.
 Since the unit for mass is grams,
and the unit for volume is ml or cm3,
then the unit for density is g/ml, or
g/ cm3
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Density Formula Wheel
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Formula wheels make it
easy to solve density
problems.
Cover the property you
are trying to find, and
do what is left over.
To find density, cover
the word density. You
have mass over volume
remaining. So divide
mass by volume to find
density!
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Mass
density
volume
Density Formula Wheel
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To find mass, you
cover the word mass.
You now have density
times volume remaining.
To find volume, cover
volume. You have mass
over density remaining,
so divide mass by
density to find volume.
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Mass
density
volume
Understanding Density
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In the following illustrations, each
will
represent 1 cm3.
Each g will represent 1 gram.
Mass = 24g
Volume = 8 cm3
g g g g
g g g g
3
Density = 3g/cm
g
g
g
g
g
g
g
g
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g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
g
•In other words, there are 3 grams in
every cm3.
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Density Problem 2
g
g
g
g
g
g
g
g
g
g
g
g
•Mass =
12 grams
•Volume = 6 cm3
•Density = 2 g/cm3
•In English we say the density of the object
is 2 grams in every cubic centimeter.
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Density Problem 3
g
g g
g
g g
g
g
g g
g
ggg
g
g
•Our previous problems were materials of
uniform density. They were the same stuff
throughout. But many materials are not.
Gravel is a great example.
•Mass = 16 grams
•Volume = 8 mL
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•Density = 2 g/mL
Water and Density
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Since 1-gram of water has a volume
of 1-mL, then the density of water
will always be 1 gram/ml.
5o-mL of water will have a mass of 50
grams, so again the density of pure
water will be 1 g/ml.
A kg of water will have a volume of
1000-mL, so it’s density will be 1
gram/ml.
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Floating and Sinking
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Less dense
materials will float
on top of more
dense materials.
Objects with a
density of less than
1-g/mL will float on
top of water.
Objects with a
density greater
than 1 g/mL will
sink in water.
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Neutral Buoyancy
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Objects with a
density equal to the
density of water will
float in mid water,
at what ever level
you place the object.
Fish and submarines
control their depth
by changing their
density.
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Objects that Sink!
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Objects with a
density greater
than 1 g/mL
will sink in
water.
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Titanic Sails the Ocean Blue
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The Titanic is sailing
on its maiden voyage.
What is the density of
this enormous, steel
hulled ship, full of
machinery, coal,
people, and all sorts of
heavy things?
It’s floating, so it’s
density must be less
than 1 g/mL.
How can this be?
The Titanic is a hollow
vessel full of air!
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Titanic verses Iceberg
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After HMS Titanic
struck the iceberg, she
started to fill with
water.
What happened to her
density?
As she took on more
and more water, her
density got closer and
closer to 1 g/mL.
The denser the ship
became, the lower she
settled into the water.
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Wreck of the Titanic
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What is the density
of the Titanic
resting on the
ocean floor?
Must be greater
than 1 g/mL, as
her steel hull is full
of water instead of
air.
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Comparing Densities
•Where is
the most
dense
object?
•Where is
the least
dense
object?
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Density Review
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We don’t actually count g’s to find the
mass of objects. How would you find
the mass of a rock?
Use a balance scale.
In real life, how would you find the
volume of a rock?
Use a graduated cylinder and see how
much water the rock displaces.
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