Metric system

Metric SystemMetric System

Scientific Scientific MeasurementsMeasurements

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Metric SystemMetric System Developed by the French in the late Developed by the French in the late

1700’s.1700’s. Based on powers of ten, so it is very easy Based on powers of ten, so it is very easy

to use.to use. Used by almost every country in the world, Used by almost every country in the world,

with the notable exception of the USA.with the notable exception of the USA. Especially used by scientists.Especially used by scientists. Abbreviated SI, which is French for Abbreviated SI, which is French for

Systeme International.Systeme International.


Metric PrefixesMetric Prefixes

Regardless of the unit, the entire Regardless of the unit, the entire metric system uses the same prefixes.metric system uses the same prefixes.

Common prefixes are:Common prefixes are:

kilo = 1000kilo = 1000

centi = 1/100centi = 1/100thth

milli = 1/1000milli = 1/1000thth

1 meter = 100 centimeters= 1000 1 meter = 100 centimeters= 1000 millimetersmillimeters


LengthLength

Length is the Length is the distance distance between two between two points.points.

The SI base unit The SI base unit for length is the for length is the metermeter..

We use rulers or We use rulers or meter sticks to meter sticks to find the length of find the length of objects.objects.


MassMass Mass is the amount of matter that makes Mass is the amount of matter that makes

up an object.up an object. A golf ball and a ping pong ball are the A golf ball and a ping pong ball are the

same size, but the golf ball has a lot more same size, but the golf ball has a lot more matter in it. So the golf ball will have matter in it. So the golf ball will have more mass.more mass.

The SI unit for mass is the The SI unit for mass is the gramgram.. A paper clip has a mass of about one A paper clip has a mass of about one

gram.gram. The mass of an object will not change The mass of an object will not change

unless we add or subtract matter from it.unless we add or subtract matter from it.


Measuring MassMeasuring Mass We will use a We will use a triple beam balancetriple beam balance

scale to measure mass.scale to measure mass. Gravity pulls equally on both sides of Gravity pulls equally on both sides of

a balance scale, so you will get the a balance scale, so you will get the same mass no matter what planet you same mass no matter what planet you are on.are on.


WeightWeight

Weight is a measure of the force of Weight is a measure of the force of gravity on an objectgravity on an object..

Your weight can change depending on Your weight can change depending on the force of gravity. The gravity will the force of gravity. The gravity will change depending on the planet you change depending on the planet you are on.are on.

The SI unit for weight is the The SI unit for weight is the NewtonNewton (N).(N).

The English unit for weight is the The English unit for weight is the pound.pound.


GravityGravity

Gravity is the force of attractionGravity is the force of attraction between between any two objects with mass.any two objects with mass.

The force depends on two things:The force depends on two things: more distance = less gravity = less weightmore distance = less gravity = less weight less distance = more gravity = more less distance = more gravity = more

weightweight more massmore mass = = more gravitymore gravity = more weight = more weight less massless mass = = less gravityless gravity = less weight = less weight


Weight and MassWeight and Mass

JillJill EarthEarth

1 1 gravitygravity

MoonMoon

1/61/6thth gravitygravity

JupiterJupiter

2.5 2.5 gravitigraviti

eses

On orbitOn orbit

0 0 gravitygravity

massmass 30kg30kg 30kg30kg 30kg30kg 30kg30kg

weightweight 300N300N 50N50N 750N750N 0 0 NewtonNewton

ss Notice that Jill’s mass never changes. Notice that Jill’s mass never changes.

Her mother will not allow us to take Her mother will not allow us to take parts off her, or add parts to her, so parts off her, or add parts to her, so

her mass stays the same. Jill is 30kg of her mass stays the same. Jill is 30kg of little girl no matter where she goes!little girl no matter where she goes!


VolumeVolume Volume is the amount Volume is the amount

of space contained in of space contained in an object.an object.

We can find the We can find the volume of box shapes volume of box shapes by the formula by the formula Volume = length x Volume = length x width x heightwidth x height

In this case the units In this case the units would be would be cubic cubic centimeters (cmcentimeters (cm33).).

So a box 2 cm x 3 cm So a box 2 cm x 3 cm x 5cm would have a x 5cm would have a volume of 30 cmvolume of 30 cm33

V = L x W x HV = L x W x Hcopyright cmassengale

Base UnitsBase Units

The base unit The base unit for volume is for volume is the the LiterLiter..

We measure We measure volume with a volume with a graduated graduated cylindercylinder..


Graduated CylindersGraduated Cylinders

Liquids form Liquids form curved, upper curved, upper surfaces when surfaces when poured into poured into graduated cylindersgraduated cylinders

To correctly read To correctly read the volume, read the volume, read the bottom of the the bottom of the curve called the curve called the meniscusmeniscus


Liquid VolumeLiquid Volume

When the metric system was When the metric system was created, they decided that 1 created, they decided that 1 cmcm33 of water would equal 1 of water would equal 1 milliliter of water and the 1 mL milliliter of water and the 1 mL of water will have a mass of of water will have a mass of one gram.one gram.

1cm1cm3 3 water =1 ml of water = 1 water =1 ml of water = 1 gramgram


Water DisplacementWater Displacement

We can use We can use water water displacementdisplacement to find to find the volume of objects the volume of objects that are not boxed that are not boxed shaped.shaped.

We can put water in a We can put water in a graduated cylinder. If graduated cylinder. If a rock causes the level a rock causes the level to rise from 7 to 9 ml, to rise from 7 to 9 ml, the the rock must have the the rock must have a volume of 2-mL.a volume of 2-mL.


Water Mass and VolumeWater Mass and Volume

1 cm1 cm3 3 water = 1 mL of water = water = 1 mL of water = 1 gram1 gram

So what would be the mass of 50 mL So what would be the mass of 50 mL of water be?of water be?

50 grams50 grams So what would be the mass of 1 liter So what would be the mass of 1 liter

of water be?of water be? 1 L = 1000 mL so its mass would 1 L = 1000 mL so its mass would

be 1000 grams or a kilogram.be 1000 grams or a kilogram.


DensityDensity Density is the amount of matterDensity is the amount of matter

(mass) (mass) compared to the amount of compared to the amount of spacespace (volume) the object occupies. (volume) the object occupies.

We will measure mass in grams and We will measure mass in grams and volume in ml or cmvolume in ml or cm33


Density FormulaDensity Formula Density is mass divided by volume.Density is mass divided by volume. Density = mass/volumeDensity = mass/volume Remember, all fractions are Remember, all fractions are

division problems. division problems. Since the unit for mass is grams, Since the unit for mass is grams,

and the unit for volume is ml or and the unit for volume is ml or cmcm33, then the , then the unit for density is unit for density is g/ml, or g/ cmg/ml, or g/ cm33


Density Formula WheelDensity Formula Wheel Formula wheels make Formula wheels make

it easy to solve it easy to solve density problems.density problems.

Cover the property Cover the property you are trying to find, you are trying to find, and do what is left and do what is left over.over.

To find density, cover To find density, cover the word density. the word density. You have mass over You have mass over volume remaining. volume remaining. So divide mass by So divide mass by volume to find volume to find density!density!

Mass

density

volume


Density Formula WheelDensity Formula Wheel To find mass, you To find mass, you

cover the word cover the word mass. You now mass. You now have density times have density times volume remaining.volume remaining.

To find volume, To find volume, cover volume. You cover volume. You have mass over have mass over density remaining, density remaining, so divide mass by so divide mass by density to find density to find volumevolume..

Mass

density

volume


Understanding DensityUnderstanding Density In the following illustrations, each will In the following illustrations, each will

represent 1 cmrepresent 1 cm33.. Each g will represent 1 gram.Each g will represent 1 gram. Mass = 24gMass = 24g Volume = 8 cmVolume = 8 cm33

Density = 3g/cmDensity = 3g/cm33 g gg g

ggg gg g

ggg gg g

ggg gg g

gg

g gg g

ggg gg g

ggg gg g

ggg gg g

gg


g gg g

ggg gg g

ggg gg g

ggg gg g

gg

g gg g

ggg gg g

ggg gg g

ggg gg g

gg

•In other words, there are 3 grams in every cmcm33..


Density Problem 2Density Problem 2

g gg g

g gg g g gg g

g gg g

g gg g

g gg g

•Mass = 12 grams

•Volume = 6 cmcm33

•Density = 2 g/cm3

•In English we say the density of the object is 2

grams in every cubic centimeter.copyright cmassengale

Density Problem 3Density Problem 3g g

g g g gg g

gg g gg g

g g g g gg

gg g g g g g gg g

gg

•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/mLcopyright cmassengale

Water and DensityWater and Density

Since 1-gram of water has a Since 1-gram of water has a volume of 1-mL, then the density volume of 1-mL, then the density of water will always be 1 gram/ml.of water will always be 1 gram/ml.

5o-mL of water will have a mass of 50 5o-mL of water will have a mass of 50 grams, so again the density of pure grams, so again the density of pure water will be 1 g/ml.water will be 1 g/ml.

A kg of water will have a volume of A kg of water will have a volume of 1000-mL, so it’s density will be 1 1000-mL, so it’s density will be 1 gram/ml.gram/ml.


Floating and SinkingFloating and Sinking Less dense Less dense

materials will float materials will float on top of more on top of more dense materials.dense materials.

Objects with a Objects with a density of less than density of less than 1-g/mL will float on 1-g/mL will float on top of water.top of water.

Objects with a Objects with a density greater than density greater than 1 g/mL will sink in 1 g/mL will sink in water.water.


Neutral BuoyancyNeutral Buoyancy

Objects with a Objects with a density equal to the density equal to the density of water will density of water will float in mid water, at float in mid water, at what ever level you what ever level you place the object.place the object.

Fish and submarines Fish and submarines control their depth control their depth by changing their by changing their density.density.


Objects that Sink!Objects that Sink!

Objects with Objects with a density a density greater than greater than 1 g/mL will 1 g/mL will sink in sink in water.water.


Titanic Sails the Ocean Titanic Sails the Ocean BlueBlue

The Titanic is sailing The Titanic is sailing on its maiden voyage.on its maiden voyage.

What is the density of What is the density of this enormous, steel this enormous, steel hulled ship, full of hulled ship, full of machinery, coal, machinery, coal, people, and all sorts people, and all sorts of heavy things?of heavy things?

It’s floating, so it’s It’s floating, so it’s density must be less density must be less than 1 g/mL.than 1 g/mL.

How can this be?How can this be? The Titanic is a The Titanic is a

hollow vesselhollow vessel full of full of air!air!


Titanic verses IcebergTitanic verses Iceberg After HMS Titanic After HMS Titanic

struck the iceberg, she struck the iceberg, she started to fill with started to fill with water.water.

What happened to her What happened to her density?density?

As As she took on more she took on more and more waterand more water, her , her density got closer and density got closer and closer to 1 g/mL.closer to 1 g/mL.

The denser the ship The denser the ship became, the lower she became, the lower she settled into the water.settled into the water.


Wreck of the TitanicWreck of the Titanic

What is the What is the density of the density of the Titanic resting Titanic resting on the ocean on the ocean floor?floor?

Must be greater Must be greater than 1 g/mL, as than 1 g/mL, as her steel hull is her steel hull is full of water full of water instead of air.instead of air.


Comparing DensitiesComparing Densities

•Where is Where is the most the most dense dense object?object?

•Where is Where is the least the least dense dense object?object?


Density ReviewDensity Review

We don’t actually count g’s to find We don’t actually count g’s to find the mass of objects. the mass of objects. How would you How would you find the mass of a rock?find the mass of a rock?

Use a balance scale.Use a balance scale. In real life, how would you find the In real life, how would you find the

volume of a rock?volume of a rock? Use a graduated cylinder and see Use a graduated cylinder and see

how much water the rock displaceshow much water the rock displaces..


Metric system

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