1. What is water? Water is: a fluid Made up hydrogen and oxygen atoms
Each water molecule contains two (2) hydrogen atoms and one (1) oxygen atom
Because of the positive hydrogen atoms on one side and negative oxygen atom on the opposite side, water molecules are attracted to each other
It has a pH of 7 (meaning it is neutral, neither acidic or basic)
It dissolves a multitude of substances and thus called a Universal Solvent because of this
On Earth it is found in three states of Solid, Liquid and Gas (Vapour) at normal Earth temperatures

2. Fresh water versus Sea water for aquatic life
Adequate dissolved oxygen is necessary for good water quality. Oxygen is a necessary element to all forms of life. Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life forms. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large fish kills.
The colder the water the more oxygen it contains
What do you think is happening with the oxygen levels and water because of Global Warming?

3. Density
All materials because they are made of atoms and molecules they contain a specific amount of mass in a specific amount of volume
For example: a block of ice that is shaped like a cube. This cube has sides of 4cm in length
And a mass of 58 grams. The density of this block of ice is:
Density = mass / volume
Density = 58g / 64cm3 = g/cm3
4cm

4. Density
Is the property of any material that gives an indication of how light or how heavy the material is.
It is defined as the mass per unit volume of the material, i.e. the amount of matter that is the volume selected.
It is represented by a symbol called rho, ρ (shaped more like an ‘e’).
Density is given by the formula:
Density = mass / volume
Ρ = m / v
Density has the units of g/cm3 or kg/m3

5. Density of water Fresh water has a density of approximately 1g/cm3
Ice has a density of approximately g/cm3
Salt water has a density of approximately g/cm3
Because ice is less dense (less heavy) than water it will float in fresh and salt water

6. weight of the water = mass x gravitational force of acceleration
Archimedes principle
States that the Upthrust (force acting upwards) acting on an object is equal to the weight of the fluid displaced.
i.e. if an object takes up the space of 1kg of water then the
weight of the water = mass x gravitational force of acceleration
(on Earth gravitational force of attraction is approximately 10ms-2)…form 3 work
Weight = 1kg x 10ms-2 = 10N
So the object will be pushed upwards with a 10 Newton force
What must be taken into consideration also would be the weight of the object acting downwards…
So if the weight of the object is 50N, what direction do you think the object will be going in the water? Upwards (towards floatation) or downwards (towards sinking?

7. Resistance to motion
Objects that are caused to move and are in contact with any other surface are moving against an opposing force
This opposing force is called friction
Friction occurs once two surfaces are in contact with each other…air and your hand, water and a ship, bike tyres and the road surface…

8. Research project
What effect does water pollution have on aquatic life?
Include eutrophication, oil spillage etc.
Cite local problems with water pollution and your suggestions on how it can be remedied.
Include possible local pictures of water pollution.
Either deliver printed work to Ms. Francis or attachment to: (if you it please confirm with Ms. Francis that I received it).
Due Friday 18th February, 2011.