Density

What is density?

• Density compares the mass of an object to its volume

Which one is more dense?• Demonstration: People in a square• How about this: Which square is more dense?

• How do you know?

Which one is more dense?

• Now which one is more dense?

• Why?

What is density?

• Density = mass OR. volume

• Units for density: g cm3

• Why are these the units for density?

ALWAYS REMEMBER

UNITS!

V

m D

To find volume, use…

1. a formula

water displacement

V = l w hV = p r2 h

V = ?

Vfinal

Vinit

Vobject = Vfinal – Vinit

2.

Equation of a Straight Line

y = mx + b

Slope Y intercept

Slope of a Straight Line

The Slope of a straight line shows how steep a straight line is.

Calculate: Divide the change in height by the change in horizontal distance

Slope = Change in YChange in X

Examples:

Volume (mL)

Mass (g) Slope = 3 g = 1 g 3mL mL

density

Volume (mL)

Mass (g)Slope = density = 4 g = 2 g 2mL mL

Solving problems in science using the GUESS strategy

G U E S S

Given Unknown Equation Substitute Solve

Let’s try a density problem together• Frank has a paper clip. It has a mass of 9g and

a volume of 3cm3. What is its density?

• Frank also has an eraser. It has a density of 3g/cm3, and a volume of 2cm3. What is its mass?

G U E S S

m= 9 gV= 3 cm3

D D= M V

D = 9g 3 cm3

3 g cm3

G U E S S

d= 3 g/cm3

V= 2 cm3

M D= M V

3 = m 2

6 g

Liquid Layers – Try with your neighbor

• Which liquid has the highest density?

• Which liquid has the lowest density?

• Which liquid has the middle density?

Liquid Layers • Check out this picture. • Which layer has the highest

density? How do you know?• Which layer has the lowest

density?• Imagine that the liquids on the

right have the following densities:– 15g/cm3 10g/cm3

– 3g/cm3 9g/cm3

– 7g/cm3 12g/cm3

• Match the colors to the correct densities.

3g/cm3

7g/cm3

9g/cm3

10g/cm3

12g/cm3

15g/cm3