1. Density

2. What is Density? Density is the mass per unit volume of a substance.
Density is measured in:
g/cm
Kg/m
g/mL.

3. When we compare the masses of the same volume of different substances we are comparing their densities.
Oil floats on water because it is less dense than water.

4. Density and the Particle Theory
Every pure substance has its own characteristic density.
Typically solids have greater densities than liquids and liquids have greater densities than gases.

5. The particle theory states that different substances have different sized particles.
The size of the particles determines how many particles can fit into a given space.
Solids are tightly packed so they have a high density, gases are spaced far apart so their density is low.

6. Mass
We can measure mass by using a balance or a digital scale.

7. Volume
Volume is a measurement of the amount of space occupied by the substance.

8. How can we measure Volume?
Liquids can be measured using a measuring cup or a graduated cylinder.
Gases can be determined by measuring the volume of the container it is in.

9. Volume
Irregular solids can be determined by immersing them into a beaker of water and measuring the volume of the displaced fluid.
4. Regular solids can be determined by measuring the length, width, and height:
V = l × w × h.

10. Displacement is the amount of space that an object takes up when placed in a fluid.

11. Changes in Density As Temperature Increases As Temperature Decreases ↓
Particles Gain Energy
Particles spread out
Decrease in Density
As Temperature Decreases ↓
Particles Lose Energy
Particles closer together
Increase in Density

12. What Portion of an Iceberg is Submerged?
Think about what happens when you add an ice cube to a glass of water?
Not all the ice floats on the surface, some of it is below the surface.
This also happens with icebergs (90% of the icebergs mass is found below the surface!)

13. Comparing Densities
By comparing densities you can calculate how much of something will be submerged.
Example: Ice and sea water
Density of Ice x 100
Density of Seawater
= x 100 = 89%
1.03
Approximately 90% of Icebergs are submerged!

14. Calculating Density
The density of a substance can be determined by calculating the mass–to– volume ratio, or density.
D = M V
Mass
Volume

15. Example
A cube of water has a volume of 2 m and a mass of 1000kg. What is the density?
Check to make sure the units can go together.
D = M = 1000kg = 500 kg/m
V m

16. Example
What is the mass of 1500 mL of helium, if the density of helium is g/mL?
m= D x V m= g/mL x 1500 mL m= 0.3 g