Chemistry - Earth's resources

What is a non-renewable resource?

A finite resource that is used up at a faster rate than it can be replenished.

What is a renewable resource?

A resource that can be replaces at the same rate at which it is used up

What is meant by sustainability?

Developments that meet the needs of society now without endangering the ability of future generations to meet their needs

Pros of recycling metals?

• conserves the limited reserves of metal ore

• process of extracting metals causes acid rain and contributes to global warming

• mining can cause visual, noise and dust pollution, large heaps of waste rocks are produces as well

What can recycled copper be used for?

electrical wiring

How are glass products recycled?

They are crushed and melted to make different glass products

What is the term for waste water?

Sewage

What is removed during sewage treatment?

Organic matter and harmful microorganisms

What the 4 stages of treating sewage water?

1. Screening

2. Primary treatment

3. Secondary treatment

4. Final treatment

What is screening for?

Removing large objects and grit

What is the primary treatment?

Sedimentation - Solid sediments settle out from the mixture. Large paddles push the solids, called sludge, to the centre where it is piped into a storage tank for further treatment. The watery liquid above the sludge is called effluent which still contains harmful microorganisms.

What is the secondary treatment?

Aerobic biological treatment - Bacteria feed on remaining organic matter and harmful microorganisms which breaks the microorganisms down aerobically so air is bubbled through the water.

What is the final treatment?

The bacteria settle to the bottom of the tank as sediment. It can now be recycled or sent to the sludge tank. The treated waste water is now safe enough to be released back into the rivers (it may be sterilised first)

How is sludge treated?

Sludge contains organic matter, human waste and dissolved compounds which are digested anaerobically by microorganisms. Dried sewage sludge takes up less space and becomes easier to transport so it can be used as a fertiliser (to improve soil) or as a source of renewable energy.

What is the term for drinking water?

Potable water

Is drinking water pure?

It isn’t pure because it contains low levels of dissolved salts and microorganisms.

What are some sources of fresh water?

Aquifers (water in underground streams), rivers, lakes, icecaps, glaciers

How is fresh water treated to make it potable?

Filtration - it is passed through filter beds made of sand/ gravel to remove solid particles

Sterilise - microorganisms are killed by adding chlorine or ozone or by passing UV rays through the water to kill them

What is the term for treating salt water?

Desalination

What are the three ways of treating salty water?

• Desalination - a type of distillation (expensive due to the cost of heating water to its boiling point)

• Flash Distillation - distillation under reduced pressure (water boils below 100^oC therefore saving some energy costs)

• Reverse osmosis - uses membranes to separate water from the salts dissolved in it (it uses no heat therefore it has lower energy costs)

What are 2 methods for extracting copper from its ore?

1. Add sulfuric acid to the ore to produce copper sulphate, before extracting the copper metal (with electrolysis or displacement)

2. Smelting - the copper ore is heated to a high temperature in a furnace with air to produce impure copper. The impure copper is then used as the positive electrode in electrolysis to make pure copper (high energy costs)

What are the anode, cathode and electrolyte for copper purification with electrolysis?

Anode - impure copper, Cathode - pure copper, Electrolyte - Solution containing copper ions

What is happening at the anode during copper purification?

Copper turns into Cu²⁺ ions therefore the mass of the anode decreases

Cu —→ Cu²⁺ + 2e^-

What is happening at the cathode during copper purification?

Cu²⁺ ions turn into pure copper therefore the mass of the cathode increases

Cu²⁺ + 2e^- —→ Cu

How do you extract copper using metal displacement?

• Copper can be extracted from copper solution by adding scrap iron. Iron can displace copper from the solution because iron is more reactive than copper.

• Fe_(s) + Cu²⁺_(aq) —→ Fe²⁺_(aq) + Cu_(s)

What is phytomining?

• Plants are grown on soil containing low grade copper ore. The plants absorb the copper ions.

• The plants are burnt and copper is extracted from copper compounds in the ash.

• The copper is extracted by adding sulfuric acid (leaching) which makes a solution of copper sulfate called a leachate.

• Displacement by scrap iron and then electrolysis to make pure copper.

What is bioleaching?

• Bacteria feed on low grade metal ores

• Bacteria produce a solution of copper ions (a leachate)

• Scrap iron is added to displace the copper and then electrolysis to make pure copper.

What are the 4 stages of the life cycle assessment?

1. Raw material production

2. Manufacturing of the product (and packaging)

3. Use / reuse / maintenance

4. Disposal (recycling / waste management)

What do you need to consider when extracting raw materials?

• If the resource is finite or renewable

• How much energy is needed for extraction

• Environmental damage/ pollution of extracting the raw material

What do you need to consider when manufacturing?

• How much energy is needed

• If the environment is damaged because of factories

• Harmful / polluting by products from the manufacture process

What do you need to consider when using a product?

• How much energy is needed

• pollution

What do you need to consider for disposal?

• Can it be recycled or reused

• will it end up in landfill

• will it damage habitats

• how much energy needed to dispose it

• Any harmful products / pollutants

What are the results of LCAs used for?

To make claims in advertising

Why should all LCAs be peer reviewed?

To check the validity