1. Density
Density is the mass of unit volume.
Unit g/cm3 or kg/m3

2. Density and flotation
If an object floats in a fluid its density is less than that of the fluid.

3. Flotation
Archimedes principle: When a body is immersed in a fluid the up thrust is equal to the weight of fluid displaced.
Law of flotation: When a body floats in a fluid, the up thrust equals the weight of fluid displaced.

4. Pressure is the force on unit area. It is measured in pascals.
Area of foot 0.1m2.
Weight 20000N.
What pressure is exerted on the ground?
Pressure is the force on unit area.
It is measured in pascals.

5. Pressure
Area of stiletto heel m2
Weight 700N
Pressure ?

6. Pressure
Area of welly heel m2
Weight 700N
Pressure ?

8. Measuring Pressure
A barometer is used to measure pressure.

9. The Mercury Barometer

10. Altimeter
An altimeter uses pressure readings to measure height.

11. Water Pressure

12. Pressure in a fluid Pressure increases with depth in a fluid.
Pressure acts equally in all directions.

13. Atmospheric pressure Caused by the weight of the atmosphere.
Decreases with height above sea level.
High pressure causes clear skies, low pressure causes cloudy skies.
To demonstrate atmospheric pressure.
Fill a glass with water and cover with a card. Invert the glass and the water does not fall out due to atmospheric pressure.

14. Low pressure causes wind and rain.
High pressure causes clear skies.
Isobars are the lines of equal pressure on weather charts.
The closer the isobars the stronger the wind.

15. Pressure and boiling point
Increasing pressure increases boiling point.
Pressure cooker
Pressure and melting point
Increasing pressure lowers melting point

16. Boyle’s Law
Boyle’s Law states that at constant temperature the pressure on a fixed mass of gas is inversely proportional to its volume.