1. Solids, liquids and gases
New unit
Solids, liquids and gases
First lesson
Density

2. DENSITY Q) Which weighs more:-
A kilogram of feathers or a kilogram of iron?
DENSITY
Objective: To describe how to determine density using direct measurements of mass and volume

3. Density is the Mass per unit Volume
What is Density?
If you take the same volume of different substances, then they will weigh different amounts.
Wood
Water
Iron
1 cm3
1 cm3
1 cm3
0.50 g
1.00 g
8.00 g
Q) Which has the greatest mass and therefore the most dense?
Density is the Mass per unit Volume

4. Density Equation: = m V m V  Mass Density = Volume Example:
g or kg m V 
Mass
Density =
Volume
g/cm3 or kg/m3
cm3 or m3
= m V
Example:
Q) Liquid water has a density of 1.0g/cm3, while ice has density of 0.92g/cm3.
Calculate the volume occupied by 250g of each.
Vwater = m = 250 = 250cm3 
Vice = m = 250 = 272cm3 

5. DENSITY OF A REGULAR SOLID
Find the Mass of the solid on a balance.
Measure the three lengths and calculate the Volume.
(ie V = l x w x h )
Calculate the Density.
m = 240 g
2.0 cm
3.0 cm
4.0 cm
 = m = 240 =10.0 g/cm3 V

6. DENSITY OF AN IRREGULAR SOLID
Find the Mass of the solid on a balance.
Find the Volume.
Calculate the Density.

7. Archimedes and the Crown
                                                                                          
Archimedes was a great scientist who lived more than 2000 years ago in a Greek city called Syracuse. He was very clever at inventing and figuring out how things work, so King Hiero needed his help many times.

8. Density of gold 20 g/cm3
1cm3 of gold has a mass of 20 g
Density of silver 10 g/cm3
1cm3 of silver has a mass of 10 g
For the same volume, gold has more mass
Silver has to have a bigger volume to have an equal mass to gold
The actual volume of the crown was 150cm3 instead of 100cm3.
Was it pure gold ??
The mass of the crown was 2000g. It should have a volume of 100cm3

9. DENSITY OF AN IRREGULAR SOLID
use a Eureka Can to find the Volume.
Find the mass of the solid on a balance.
Add water until just overflowing.
Place a Measuring Cylinder under the spout.
Add the Object.
Collect the Water and read off the Volume.
Calculate Density
m = 440 g
40.0 cm3
 = m = 440 =11.0 g/cm3 V

10. Carry out an experiment to measure the density of two regular and two irregular objects
Material
Mass
in g
Length
in cm
Width
Height
Volume
in cm3
Density
in g/cm3
Material
Volume
in cm3
Density
in g/cm3
Irregular objects

11. Quiz

12. Which block X or Y has the greater mass?
5400 kg
2m3
7800 kg
1m3 X Y X

13. Which block X or Y has the greater volume?
5400 kg
2m3
7800 kg
1m3 X Y Y

14. Which block X or Y has the greater density?
5400 kg
2m3
7800 kg
1m3 X Y X

15. Density of Petrol = 800kg/m3
Density of water = 1000 kg/m3
Which has more mass 1m3 of petrol of 1m3 of water?
1m3 of water

16. Density of Petrol = 800kg/m3
Density of water = 1000 kg/m3
Which has more volume (takes up more space) 1kg of petrol of 1kg of water?
1kg of petrol

17. Last q
The density of Aluminium is 2700kg/m3. what is the mass of 10m3 of Aluminium?
= m V
Mass = x 10
= kg

18. DENSITY
Objective: To describe how to determine density using direct measurements of mass and volume.
Homework: Read pages in the textbook and answer the questions