DENSITYDENSITY

Q) Which weighs more:-A kilogram of feathers or a kilogram of iron?

What is Density?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 will weigh different

amounts.

0.50 g 1.00 g 8.00 g

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

IRON

Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume. Its unit is g/cm3 or kg/m3

Density

Density = MassVolume

g or kg

cm3 or kg3

gcm-3 or kgm-3

= m V

Example:Q) Liquid water has a density of 1000kgm-3, while ice has density of 920kgm-3. Calculate the volume occupied by 0.25kg of each.

Density Equation:

m

V

V = m = 0.25 = 0.000250m3

1000V = m = 0.25 = 0.000272m3

920

Change Mass AND Keep Volume SameChange Mass AND Keep Volume Same

Increase the mass Increase the mass increases increases densitydensity

Decrease the mass Decrease the mass decreases decreases densitydensityWhich container has more density?Which container has more density?

AA BB

Ways to Affect Density

Change Volume AND Keep Mass SameChange Volume AND Keep Mass Same

Increase the volume Increase the volume decreases decreases densitydensity

Decrease the volume Decrease the volume increases increases densitydensityWhich container has more density?Which container has more density?

A B A B

Ways to Affect Density

DENSITY OF A REGULAR SOLIDDENSITY OF A REGULAR SOLID

Find the Mass Find the Mass of the solid on of the solid on a balance.a balance.

Measure the Measure the three lengths three lengths and calculate and calculate the Volume.the Volume.

(ie V = l x w x h )(ie V = l x w x h ) Calculate the Calculate the

Density.Density.4.0 cm

2.0 cm

3.0 cm

= m = 240 =10.0 g/cm3

V 24

m = 240 g

DENSITYDENSITY g/cmg/cm33

AluminiumAluminium 2.702.70

BrassBrass 8.508.50IronIron 7.867.86

WoodWood 0.500.50SlateSlate 2.802.80GlassGlass 2.502.50LeadLead 11.311.3MarbleMarble 2.702.70WaxWax 0.890.89

DENSITY OF AN IRREGULAR DENSITY OF AN IRREGULAR SOLIDSOLID

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

50 cm3

80 cm3

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

V 30

DENSITY OF A FLOATING DENSITY OF A FLOATING OBJECTOBJECT

Find the Mass of the object Find the Mass of the object on a balance.on a balance.Add some amount of Water Add some amount of Water to a Measuring Cylinderto a Measuring Cylinder Add only the steel ball firstAdd only the steel ball first Find the Volume of Water Find the Volume of Water Now add the steel ball Now add the steel ball along with the objectalong with the objectFind the volume of water Find the volume of water displaceddisplacedCalculate the Density.Calculate the Density.

50 cm3

80 cm3

m = 36 g

= m = 36 =3.6 g/cm3

V 10

90 cm3

DENSITY OF A LIQUIDDENSITY OF A LIQUID Find the Mass of an empty Find the Mass of an empty

Measuring Cylinder.Measuring Cylinder. Add a certain Volume of Add a certain Volume of

Liquid.Liquid. Find the Mass of the Find the Mass of the

Measuring Cylinder and LiquidMeasuring Cylinder and Liquid Calculate the Mass of Liquid.Calculate the Mass of Liquid. How?How? Calculate Density of Liquid.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

If you have 2 or more liquids,

the MORE dense liquid will be on bottomThe LESS dense liquid will be on top

Let’s try some density problems Let’s try some density problems togethertogether

1 Frank has a paper clip. It has a mass of 9g 1 Frank has a paper clip. It has a mass of 9g

and a volume of 3cmand a volume of 3cm33. What is its density?. What is its density?

2. Frank also has a pen. It has a mass of 3g, 2. Frank also has a pen. It has a mass of 3g, but he doesnot know the volume. Explain but he doesnot know the volume. Explain how he can find the density by giving how he can find the density by giving appropriate values as examples.appropriate values as examples.

Super Scientist Question of the Day

• Jake has a book, a ruler, and a balance.

• • How can Jake find the density

of the book with the tools he has?