everyone ever tell you are dense? well, you all are… well, you all are… because you all have...

Everyone Ever Tell You are Dense?

Well, you all are…

Because you all have these two properties

You are made up of MATTER…which means you have mass

You all have VOLUME…which means you take up space

When You Combine Mass and Volume, you get…

Density

A measure of the amount of matter that occupies a given amount of space

SPACE

Amount of Matter

DensityAim: How is density determined?

What is Density?

• Which one is more dense, a bowling ball or a soccer ball?• Even though they are both approximately the same size and

shape, the bowling ball is much more dense.

Density

• Therefore, density depends on the mass of particles and how closely packed they are.

• Density = Mass Volume

Let’s put it all together…

• DENSITY is the ratio of the mass of a substance to the volume of the substance

UNITS: commonly expressed as grams per cubic centimeter for solids and liquids and grams per liter for gases

So now you’re going to say we need more units, right?

Right!!!!

Units for Density =

Grams per cubic centimeter

g/cm3

What Do All Those Letters Mean?

Quick Visual Aid

Want to See An Example Question?

An unknown object has a mass of 15 grams and a volume of 5 cm3. What is the density of this object?

Density = Mass ÷ Volume

Density = 15 grams ÷ 5 cm3

Density = 3.0 g/cm3

Your Turn!!!

An unknown liquid has a volume of 6 cm3 and a mass of 6 grams. What is the density of this liquid?

Density = Mass ÷ Volume

Density = 6 grams ÷ 6 cm3

Density = 1.0 g/cm3

Find the Density of the Cube

10 cm3 cm

8 cmMass = 480 grams

480 g

240 cm3

= 2 g/cm3

Density Problems

• Calculate the density of a rock that has a mass of 40 grams and a volume of 5 cm3.

• 40g/5 cm3 = 8 g/cm3

• An unknown sample has a density of 8 g/cm3. If the mass of the sample is 16 grams, what is its volume?

• 8 g/cm3 = 16g/V = 2 cm3

• An unknown sample has a density of 10 g/cm3 and a volume of 2 ml. What is the mass of the sample?

• 10 = M/2 ml = 20 g

Density Facts

• The Density of a substance remains the same regardless of size, shape, or mass of sample!!!

• Example: The density of a piece of aluminum is 2.7 g/cm3. • If you cut the Al bar in half, the density of each piece is still 2.7

g/cm3

• Even if you roll the aluminum into a sheet the density will still remain the same

Density of Aluminum

D = 2.7 g/cm3D = 2.7 g/cm3

By simply cutting the bar in half, the density remains the same!!!

What will change the density of an object?

• Temperature• As the temperature of a substance INCREASES the

density DECREASES due to the expansion of the substance

Inverse Relationship

Most substances EXPAND when heated and CONTRACT when cooled

• Warm air rises because it is LESS dense• Cold air sinks because it is MORE dense

What will change the density of an object?

• PRESSURE• As pressure on a substance INCREASES the density

INCREASES

DIRECT RELATIONSHIP

• Material DENSER than water will SINK in water

• Material LESS DENSE than water will FLOAT

• Materials with a density EQUAL TO water may remain at ANY LEVEL

• When several objects of different densities float on water, the LEAST DENSE objects float HIGHEST.

A B

C

D

Water: 1 g/ml

Object D: 2 g/cc

Object C: 1 g/cc

Object B: 0.4g/cc

Object A: 0.8g/cc

Volume (cc)

Mas

s (g

)

DC

A

B