Density

Volume

• The volume of an object is the amount of space it takes up

• The SI unit of volume is the cubic metre (m3) or cubic centimetre (cm3). The Litre is also used (1L = 1000cm3)

• Graduated Cylinders, burettes, & pipettes are used to measure the volume of a liquid

Measuring the Volume of a Liquid

50

40

30

20

10

0

Burette

Pipette

Graduated Cylinders

• The volume of a liquid is read from the lowest part of the Meniscus (curve)

Measuring the Volume of a Liquid

• The volume of regular solids e.g. cubes, can be found by simply measuring their length, width, & height and using the formula

Measuring the Volume of a Solid

Volume = Length x Width x Height

Remember…….

• 1m3 = 1m x 1m x 1m

• 1m3 = 100cm x 100cm x 100cm

• 1m3 = 1,000,000 cm3

Measuring the Volume of a Solid

• A displacement can and a graduated cylinder is used to find the volume of a solid with an irregular shape

Mass

• The mass of an object is the amount of matter in it

Density

•The density of a substance is its mass per unit volume

•Density = Mass/Volume

Density = Mass Volume

D = M/V

M

D V

Measured in kilograms per metre cubed (kg/m3)

Also g/cm3

Density

DENSITY

Mandatory Experiment

Density of a Solid Rectangular Block

Desity of a irregular Solid

Density of a Liquid

What is Density?

Density is the Mass per unit Volume

Wood Water Iron

1 cm3 1 cm3 1 cm3

If you take the same volume of different substances, then they can have different

masses

0.50 g 1.00 g 8.00 g

Q) Which has the greatest mass and therefore the most dense?

IRON

DENSITY OF A REGULAR SOLID

• Find the Mass of the solid on a balance.

• Measure the three lengths and calculate the Volume.

(ie V = l x w x h )• Calculate the

Density.4.0 cm

2.0 cm

3.0 cm

= m = 240 =10.0 g/cm3

V 24

m = 240 g

MateriaMateriall

MassMass

in gin gLengthLength

in cmin cmWidthWidth

in cmin cmHeight Height

in cmin cmVolumeVolume

in cmin cm33

DensityDensity

in in g/cmg/cm33

DENSITYDENSITY g/cmg/cm33

AluminiumAluminium 2.702.70

BrassBrass 8.508.50

IronIron 7.867.86

WoodWood 0.500.50

SlateSlate 2.802.80

GlassGlass 2.502.50

LeadLead 11.311.3

MarbleMarble 2.702.70

WaxWax 0.890.89

DENSITY OF AN IRREGULAR SOLID

Find the Mass of the solid Find the Mass of the solid on a balance.on a balance.Fill the Measuring Cylinder Fill the Measuring Cylinder with Water to a known with Water to a known Volume.Volume. Add the Object.Add the Object. Work out the Volume of Work out the Volume of Water that is displaced.Water that is displaced. Calculate the Density.Calculate the Density.

50 cm3

80 cm3

m = 360 g = m = 360 =12.0 g/cm3

V 30

DENSITY OF AN IRREGULAR SOLID

• OR use a Eureka Can to find the Volume. Find the mass of the solid on Find the mass of the solid on a balance.a balance.Add water until just Add water until just overflowing.overflowing. Place a Measuring Cylinder Place a Measuring Cylinder under the spout.under the spout. Add the Object.Add the Object. Collect the Water and read off Collect the Water and read off the Volume.the Volume.Calculate DensityCalculate Density

m = 440 g

40.0 cm3

= m = 440 =11.0 g/cm3 V 40

DENSITYDENSITY g/cmg/cm33

AluminiumAluminium 2.702.70

IronIron 7.867.86

BrassBrass 8.508.50

WoodWood 0.500.50

SlateSlate 2.902.90

GlassGlass 2.502.50

DENSITY OF A LIQUID• Find the Mass of an empty

Measuring Cylinder.• Add a certain Volume of Liquid.• Find the Mass of the Measuring

Cylinder and Liquid• Calculate the Mass of Liquid.• How?• Calculate Density of Liquid.

Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of

empty Measuring Cylinder

25.0 g

20.0 cm3

45.0 g

45 – 25 = 20 g = m = 20 =1.00 g/cm3 V 20

LiquidLiquid Mass of Mass of empty empty

MeasurinMeasuring g

CylinderCylinder

in gin g

Mass of Mass of MeasurinMeasurin

g g Cylinder Cylinder

and and LiquidLiquid

in gin g

Mass of Mass of LiquidLiquid

in gin g

VolumeVolume

in cmin cm33

DensityDensity

in g/cmin g/cm33

DENSITY OF A GAS

• Remove the air from a flask of a known Volume, using a vacuum pump.

• Find its Mass.• Add the gas to be

tested.• Reweigh.• The difference is the

Mass of gas.• Calculate Density.

To vacuum flask

1000 cm3

150.0 g170.0 g

= m = 20 =0.0200 g/cm3 V 1000

170 -150 = 20.0g

Flotation

Flotation

• An object will float if it is less dense than the liquid

• An object will sink if it is more dense than the liquid

• One liquid can float on top of another e.g oil floats on water

Density is the amount of mass in a particular volume

Density =

g/ cm3

Mass (g)

Volume (cm3)

A B

Diagram B shows a greater density than diagram A because there is more mass in the same volume.

If a substance is more dense than water then it will sink

If a substance is less dense than water then it will float

Dancing Raisins

• http://www.youtube.com/watch?v=tx4x6Qsyr4o

Experiment with the coke and diet coke

• http://www.youtube.com/watch?v=N8DV_B4GJ48

• Mythbusters• http://www.youtube.com/watch?

v=I_F2pTvJfUs

Your Task

• Design an experiment that effects the density of your object .

• You have to make objects float that usually sink

• Remember salt has particles!.

Can I Make an object Sink?

• If an object originally floats can I make it sink?• http://www.youtube.com/watch?v=hp9d7G-

vU_o&feature=related

Homework

• Workbook Pg 134 Q8 9 10• Workbook Pg 135 Q 9 10

Q

• Why does one balloon float and the other Sinks?

Explain why this man floats in the dead sea?

Homework

• Pg 248 of text book • Q 1,2,4,6,7,8

• Density Experiment