Unformatted text preview: Metric System
Metric
Scientific
Scientific
Measurements
Measurements
copyright cmassengale Metric System
Metric 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. copyright cmassengale Metric Prefixes
Metric
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 copyright cmassengale Length
Length Length is the
Length
distance between
two points.
two
The SI base unit
The
for length is the
meter.
meter
We use rulers or
We
meter sticks to
find the length of
objects.
objects.
copyright cmassengale Mass
Mass Mass is the amount of matter that
Mass
makes up an object.
makes
A golf ball and a ping pong ball are the
golf
same size, but the golf ball has a lot
more matter in it. So the golf ball will
have more mass.
have
The SI unit for mass is the gram.
The
gram
A paper clip has a mass of about one
paper
gram.
gram.
The mass of an object will not change
The
unless we add or subtract matter from
it.
it.
copyright cmassengale Measuring Mass
Measuring We will use a triple beam balance scale to
We
triple
measure mass.
measure
Gravity pulls equally on both sides of a
Gravity
balance scale, so you will get the same mass
no matter what planet you are on.
no copyright cmassengale Weight
Weight 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. copyright cmassengale Gravity
Gravity 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
copyright cmassengale Weight and Mass
Weight
Jill Earth Moon Jupiter On orbit 1 gravity 2.5 gravities
30kg 0 gravity 750N 0 Newtons mass 30kg 1/6th gravity
30kg weight 300N 50N 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! copyright cmassengale Volume
Volume Volume is the amount
Volume
of space contained in
an object.
an
We can find the volume
We
of box shapes by the
formula Volume =
length x width x height
length
In this case the units
In
would be cubic
centimeters (cm3).
centimeters
So a box 2 cm x 3 cm x
So
5cm would have a
volume of 30 cm3
volume
copyright cmassengale V=LxWxH Base Units
Base
The base unit for volume is the Liter. We measure volume with a graduated cylinder. copyright cmassengale Graduated Cylinders
Graduated
Liquids form curved,
Liquids
upper surfaces when
poured into
graduated cylinders
graduated To correctly read the
To
volume, read the
bottom of the curve
called the meniscus
meniscus copyright cmassengale Liquid Volume
Liquid
When the metric system was created,
When
they decided that 1 cm3 of water
they
would equal 1 milliliter of water and
the 1 mL of water will have a mass of
one gram.
one 1cm3 water =1 ml of water = 1 gram
water copyright cmassengale Water Displacement
Water We can use water
We
displacement to find the
displacement
volume of objects that
are not boxed shaped.
are
We can put water in a
We
graduated cylinder. If a
rock causes the level to
rise from 7 to 9 ml, the
the rock must have a
volume of 2mL.
volume
copyright cmassengale Water Mass and Volume
Water 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
1000 grams or a kilogram.
1000 copyright cmassengale Density
Density Density is the amount of matter (mass)
compared to the amount of space (volume)
compared
the object occupies.
the
We will measure mass in grams and
We
volume in ml or cm3
volume copyright cmassengale Density Formula
Density
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 copyright cmassengale Density Formula Wheel
Density Formula wheels make it
Formula
easy to solve density
problems.
problems.
Cover the property you
Cover
are trying to find, and
do what is left over.
do
To find density, cover
To
the word density. You
have mass over volume
remaining. So divide
mass by volume to find
density!
density!
copyright cmassengale Mass
density volume Density Formula Wheel
Density To find mass, you cover
To
the word mass. You
now have density times
volume remaining.
volume
To find volume, cover
To
volume. You have
mass over density
remaining, so divide
mass by density to find
volume.
volume copyright cmassengale Mass
density volume Understanding Density
Understanding In the following illustrations, each will represent 1 cm3.
Each g will represent 1 gram.
Mass = 24g
Volume = 8 cm3
Density = 3g/cm3
g g
g g
g g
g g g
g g g
g g g
g g g
g g g g g g copyright cmassengale 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. copyright cmassengale Density Problem 2
Density
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. copyright cmassengale Density Problem 3
Density
g g g g
g g g g g g g g g g 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
•Density = 2 g/mL
copyright cmassengale Water and Density
Water Since 1gram of water has a volume of
Since
1mL, then the density of water will
always be 1 gram/ml.
always
5omL 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 1000mL, so it’s density will be 1 gram/ml. copyright cmassengale Floating and Sinking
Floating Less dense
Less
materials will float
on top of more
dense materials.
dense
Objects with a
Objects
density of less than
1g/mL will float on
top of water.
top
Objects with a
Objects
density greater than
1 g/mL will sink in
water.
water.
copyright cmassengale Neutral Buoyancy
Neutral 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. copyright cmassengale Objects that Sink!
Objects Objects with a
Objects
density greater
than 1 g/mL will
sink in water.
sink copyright cmassengale Titanic Sails the Ocean Blue
Titanic The Titanic is sailing on
The
its maiden voyage.
its
What is the density of
What
this enormous, steel
hulled ship, full of
machinery, coal,
people, and all sorts of
heavy things?
heavy
It’s floating, so it’s
It’s
density must be less
than 1 g/mL.
than
How can this be?
The Titanic is a hollow
The
vessel full of air!
vessel
copyright cmassengale Titanic verses Iceberg
Titanic After HMS Titanic
After
struck the iceberg, she
started to fill with water.
started
What happened to her
What
density?
density?
As she took on more
As
and more water, her
and
her
density got closer and
closer to 1 g/mL.
closer
The denser the ship
The
became, the lower she
settled into the water.
settled
copyright cmassengale Wreck of the Titanic
Wreck What is the density
What
of the Titanic resting
on the ocean floor?
on
Must be greater than
Must
1 g/mL, as her steel
hull is full of water
instead of air.
instead copyright cmassengale Comparing Densities
Comparing
•Where is
Where
the most
dense
object?
object?
•Where is
Where
the least
dense
object?
object? copyright cmassengale Density Review
Density 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. copyright cmassengale copyright cmassengale ...
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 Winter '11
 Harmon
 International System of Units, Kilogram, copyright cmassengale, Density Review

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