Water & Enviro Week 2

Good quality water should be free from

1. Visible suspended matter

2. Excessive colour, taste & odour

3. Objectionable dissolved matter

4. Contaminants / Pollutants

5. Bacteria indicative of poo

Waters chemical properties

2 hydrogen atoms joined by covalent bond to 1 oxygen atom

Bonding between different atoms results in electrons being unevenly shared between atoms, creating:

Polar covalent bonds

Water has _______ bonds

Polar covalent

How are waters bonds formed

Oxygen atom has higher electronegativity than hydrogen - attracts electrons to nucleus making oxygen partially negative

How are hydrogen bonds formed

Charge difference causes water molecules to be attracted to eachother

True or false: Solid water (ice) is more dense than liquid

False

At <__ degrees molecules no longer move enough to break hydrogen bonds, locking into a lattice at __ degrees.

<4 degrees, 0 degrees

Ice has ______ hydrogen bonds, whereas liquids hydrogen bonds ______

Ice has stable bond, liquids constantly break and reform

High surface tension results from

Attractive forces between water molecules

Surface tension is

The force required to break the “film” on surface of fluid

Waters specific heat is

4.184 joules (Higher than any common substance)

It takes ______ to convert water from liquid to gas

heat energy

How does heat energy change liquid to gas

Increased speed of water molecules breaking hydrogen bonds allowing molecules to escape into the air

Ions are

Atoms which have lost electrons

Ionic compounds are

Oppositely charged ions attracted to eachother by electrostatic forces

Why do ionic compounds dissolve

Charged regions of polar water molecules are attracted to oppositely charged ions.

How do ionic compounds dissolve in water

Water surrounds individual ions, separating them from one another & preventing them from bonding

Substances which readily dissolve in water are

Hydrophillic

Do non polar compounds dissolve in water

No - water molecules are not attracted as there is no attraction of opposite charges

Substances which do not dissolve in water are called

Hydrophobic

Distillation is

Liquid to gas phase to achieve separation

Precipitation is

Dissolved compounds combine to form a solid phase

Suspended particles are

Solid particles in water

Sedimentation can occur when

Particles are large enough to settle out of solution

Colloidal substances is

The range between dissolved & suspended

Increases in water temperature result in

1. Reduced gas solubility

2. Increases rate of chemical & biological process

3. Alter sensitivity of organisms to pollution

Thermal stratification is

Temperature dependent layering due to differing water density

Summer

Increased air temperature rapidly warms surface water

Epilimnion

When colder dense water sinks to the bottom

Hypolimnion

Minimal sunlight & oxygen, no mixing with upper layers

Thermocline

Transition zone between layers where temperatures and density change occurs

Autumn and spring have ______ water temperature

Uniform

Winter

Air temperature decreases - stratification occurs

Odour & taste threshold tests can be

Dilution number or threshold number at set temperature

Causes of taste and odour

1. Decaying vegetation

2. Mold

3. Iron and sulphur bacteria

4. Sodium chloride

5. Industrial waste

6. Chlorination

Apparent colour

Whole water sample dissolved & suspended material

True colour

Water filtered through fine filter to remove all suspended colour then measure colour