1 of 17

DENSITY

D = m/v (g/cm³)

Mass usually expressed in grams
Volume usually expressed in cm³or ml etc.

Density = amount of matter per unit volume

2 of 17

The “DMV” Triangle for�Volume, Mass, and Density

M

÷ ÷

D X V

Density =

M

V

Volume =

M

D

Mass =

D x V

3 of 17

What would take up more space??? A kilogram of feathers…..�or a kilogram of steel??

OR

4 of 17

Density is the measure of the “compactness” of a material

How close the atoms or molecules are to each other
More than “heaviness” - density includes how much space an object takes up!!
All substances have density including liquids, solids, and gases

5 of 17

“Compactness”

6 of 17

Gases

How much kinetic energy do the molecules have??
The greater the kinetic energy
……the greater the volume
…… and the less dense that gas is!!

Therefore, cold air is more dense than warm air

�

7 of 17

Low pressure weather system means warmer air tends to rise,

High pressure systems indicate a colder more dense air mass that will……. SINK!!!�

8 of 17

LIQUIDS

The more dissolved solids in a solution, the more dense (such as ocean water)
Cold water in lakes tend to sink (this creates a constant mixing of water, nutrients, and other substances)

Kinetic energy again!!

Denser layers to less dense layers…..

9 of 17

What would happen????

Mercury density = 13600kg/m³
Lead density = 11340kg/m³

10 of 17

Lead floats on liquid mercury!

11 of 17

Solids

Ice vs. water…..

12 of 17

SOLIDS

Ice is less dense than water (which is why lakes and ponds have a thin layer of ice covering in winter, with water underneath)
Various rocks, woods, metals have a characteristic density specific to that substance

Wouldn’t you like to have a bunch of THIS dense material?

13 of 17

Archimedes and the Kings Crown

14 of 17

Factors affecting Density

Temperature

Pressure

Add several drops of red food color to each of two 250-mL Erlenmeyer flasks; fill them with warm tap water. (If tap water is not warm, heat some tap water on a hot plate to 40-45 °C.)

Add several drops of blue food coloring to each of the other two 250-mL Erlenmeyer flasks; fill them with cool tap water.

Predict the outcome when one flask is inverted over the other.

Place a paper card on top of the vessel filled with warm water. Invert the flask making sure to hold the card in place. Stack it on top of one of the cool water flasks. Remove the card. Remain prepared to catch the flasks.

** Visual here.

Place a paper card on top of the flask filled with cool water. Invert the flask making sure to hold the card in place. Stack it on top of the other warm water flask. Remove the card.

** Visual here.

Wide mouth containers may also be used.

15 of 17

Factors affecting Density

Dissolved solids – in liquids

Concentration and kind of substances

16 of 17

DETERMINING DENSITY

Regular Shapes – mass, then determine the volume by formula

EX: cubes, cylinders, spheres, cones, etc.

Irregular shapes – mass, then measure displacement of a liquid (usually water) by that irregularly shaped object

Use a graduated cylinder
Add water to a predetermined level - record.
Gently drop in the irregularly shaped object.
Read the graduated cylinder – record.
Subtract the first water level from the second – this is the volume

17 of 17

Density Table

SINK or FLOAT

In Water (D = 1.0 g/mL)

Float

Sink

Float

(alcohol)

(fuel)