topic 10 - Using Resources

What are Earth's natural resources?

Materials and substances obtained from the Earth, including water, air, rocks, minerals and fuels.

What is a finite resource?

A resource that is used faster than it is naturally replaced, so supplies will eventually run out.

What is a renewable resource?

A resource that is naturally replenished as it is used.

Give examples of finite resources.

Crude oil, coal, natural gas and metal ores.

Give examples of renewable resources.

Timber from sustainably managed forests and resources such as wind and solar energy.

What is sustainable development?

Development that meets the needs of current generations without preventing future generations from meeting their own needs.

Why do chemists aim to use resources sustainably?

To conserve finite resources, reduce energy use and waste, and minimise environmental damage.

What is meant by sustainable use of resources?

Using resources efficiently so they are available for future generations and environmental impacts are reduced.

Why is recycling important?

It reduces the need to extract new raw materials, saves resources and can reduce energy use and waste.

What is potable water?

Water that is safe to drink because it contains sufficiently low levels of dissolved salts and microbes.

Is potable water chemically pure water?

No. Potable water contains small amounts of dissolved substances, whereas pure water contains only H₂O.

What is the difference between potable water and pure water?

Potable water is safe to drink but contains dissolved substances. Pure water contains only water molecules.

How is most potable water produced in the UK?

Choose a suitable source of fresh water, pass it through filter beds, then sterilise it.

What is the purpose of choosing a suitable source of fresh water?

Water from suitable rivers, lakes or groundwater usually contains relatively low levels of dissolved substances and is easier to treat than seawater.

What does filtration remove during water treatment?

Solid particles and suspended insoluble material.

What is sterilisation in water treatment?

The process of killing harmful microbes in water.

Name three methods used to sterilise potable water.

Chlorine, ozone and ultraviolet light.

Why is water sterilised before drinking?

To kill harmful microorganisms that could cause disease.

Why is filtration alone not enough to make water potable?

Filtration removes suspended solids but does not necessarily remove dissolved substances or kill harmful microbes.

How can salty water be made potable?

Remove dissolved salts by desalination, using distillation or reverse osmosis, then ensure the water is safe to drink.

What is desalination?

The removal of dissolved salts from seawater or salty water.

How does distillation produce fresh water from seawater?

Heat the seawater so water evaporates, leaving dissolved salts behind; cool the water vapour so it condenses into liquid water.

Why does distillation separate water from dissolved salts?

Water evaporates and condenses, but the dissolved salts do not evaporate with it under these conditions.

What is reverse osmosis?

A desalination method in which pressure forces water through a membrane that prevents most dissolved salts from passing through.

What is one disadvantage of desalination?

It requires substantial energy, making it expensive and potentially increasing environmental impacts.

Why is groundwater often easier to treat than seawater?

Groundwater usually contains much lower concentrations of dissolved salts than seawater.

What is the aim of the required practical on water samples?

To analyse and purify water samples from different sources, including investigating pH and dissolved solids and using distillation.

How can you test the pH of a water sample?

Use a suitable pH indicator or a pH meter.

How can you estimate the amount of dissolved solids in a water sample?

Measure a known volume, evaporate the water and measure the mass of the remaining solid residue.

Why must the volume of water be measured in the dissolved-solids practical?

So samples can be compared fairly using the same volume, or results can be calculated per unit volume.

How can you purify a water sample by distillation in the laboratory?

Heat the sample, pass the vapour through a condenser and collect the condensed liquid separately.

What is one safety precaution when distilling water?

Wear eye protection and take care with hot apparatus and glassware.

What is wastewater?

Water that has been used in homes, industry or agriculture and contains waste substances.

Why must wastewater be treated before being released into the environment?

To remove harmful substances and microbes that could pollute water and damage ecosystems or human health.

What types of wastewater may need treatment?

Sewage, agricultural wastewater and industrial wastewater.

What may industrial wastewater contain?

Organic matter and harmful chemicals that must be removed or reduced before discharge.

What are the main stages of sewage treatment?

Screening and grit removal, sedimentation, anaerobic digestion of sewage sludge, and aerobic biological treatment of effluent.

What happens during screening in sewage treatment?

Screens remove large solid objects from the wastewater.

What is grit removal?

The removal of heavy particles such as sand and grit from wastewater.

What happens during sedimentation in sewage treatment?

Solids settle out of the wastewater, forming sewage sludge, while the remaining liquid is called effluent.

What is sewage sludge?

The solid material that settles out during sedimentation.

What is effluent?

The liquid remaining after solids have been removed from sewage.

What happens during anaerobic digestion of sewage sludge?

Microorganisms break down organic matter in the absence of oxygen.

What does anaerobic mean?

Without oxygen.

What happens during aerobic biological treatment of effluent?

Aerobic microorganisms break down organic pollutants in the presence of oxygen.

What does aerobic mean?

In the presence of oxygen.

Why is oxygen needed during aerobic treatment?

Aerobic microorganisms use oxygen while breaking down organic matter.

What is one difference between anaerobic and aerobic treatment?

Anaerobic digestion takes place without oxygen; aerobic biological treatment takes place in the presence of oxygen.

Why can wastewater treatment be complicated?

Different wastewaters contain different pollutants, and some industrial chemicals require specialist treatment.

Which water source is generally easiest to make potable: groundwater, seawater or wastewater?

Suitable groundwater is often easiest because it generally contains fewer dissolved salts and less contamination than seawater or wastewater.

Why is wastewater often harder to treat than groundwater?

Wastewater can contain organic matter, microbes and chemicals that must be removed or treated.

What are metal ores?

Rocks that contain enough metal compounds for the extraction of metals to be economically worthwhile.

Why are metal ores finite resources?

There is a limited amount of accessible ore, and natural processes do not replace it quickly enough.

Why are some copper ores becoming less useful for traditional extraction?

High-grade ores are becoming scarce, leaving lower-grade ores that contain less copper.

What is a low-grade ore?

An ore containing a relatively low concentration of the desired metal compound.

What are two alternative biological methods of extracting copper from low-grade ores?

Phytomining and bioleaching.

What is phytomining?

A method of extracting metals in which plants absorb metal compounds from the soil.

Describe the stages of phytomining.

Plants absorb metal compounds from the soil; the plants are harvested and burned; the ash contains metal compounds that can then be processed to obtain the metal.

Why are plants burned during phytomining?

Burning removes much of the plant material and leaves ash containing concentrated metal compounds.

What is bioleaching?

A method in which bacteria produce solutions containing dissolved metal compounds from ores.

What is leachate in bioleaching?

The solution containing dissolved metal compounds produced during the process.

How can copper be obtained from a solution containing copper compounds?

Use displacement with scrap iron or extract copper by electrolysis.

How does scrap iron extract copper from a copper compound solution?

Iron is more reactive than copper, so it displaces copper from the solution and copper metal forms.

Why can electrolysis be used to obtain copper from a solution of copper compounds?

The electrical current causes copper ions to gain electrons and form copper metal at the cathode.

What is one advantage of phytomining?

It can extract metals from low-grade ores and contaminated land without moving as much rock as traditional mining.

What is one disadvantage of phytomining?

It can be slow because plants need time to grow and absorb the metal compounds.

What is one advantage of bioleaching?

It can extract metals from low-grade ores that may not be economical to process using traditional methods.

What is one disadvantage of bioleaching?

It can be slow and may produce acidic solutions that need careful management to avoid environmental harm.

Why might biological metal extraction be more sustainable than traditional mining?

It can reduce the need to dig up, move and dispose of large amounts of rock.

Why should alternative metal-extraction methods be evaluated rather than automatically called better?

Their costs, speed, energy use, yields and environmental effects must be compared with those of traditional extraction.

What is a life-cycle assessment (LCA)?

An assessment of the environmental impacts associated with a product at each stage of its life.

What are the four main stages considered in a life-cycle assessment?

Extracting and processing raw materials; manufacturing and packaging; use and operation; disposal at the end of its useful life.

What should be considered at every stage of an LCA?

Energy and water use, use of resources, waste produced, pollution and transport or distribution impacts.

Why is transport included in a life-cycle assessment?

Transport uses energy and may produce greenhouse gases and other pollutants.

What is the purpose of a life-cycle assessment?

To compare products and identify ways of reducing their environmental impact.

Why is an LCA not completely objective?

Some impacts, especially pollution and environmental damage, are difficult to quantify and require value judgements.

What is an abbreviated LCA?

An assessment that considers only selected stages or impacts of a product's life cycle.

How can an abbreviated LCA be misleading?

It may leave out important stages or impacts and present a product as more environmentally friendly than it really is.

How can an LCA be used in advertising unfairly?

A company might select only the data that supports its product and ignore unfavourable impacts.

What should you consider when comparing two LCAs?

Check that the same stages and types of impact are included and that the data and assumptions are comparable.

What is a comparative LCA?

An assessment comparing the environmental impacts of two or more products over their life cycles.

How could you compare paper and plastic shopping bags using an LCA?

Compare raw material extraction, manufacture, transport, use and disposal, including energy, water, resources and waste at each stage.

Why might paper bags have environmental disadvantages?

Paper production can require trees, water and energy, and paper bags may be heavier to transport.

Why might plastic bags have environmental disadvantages?

They are made from finite fossil-fuel resources and can persist in the environment if discarded carelessly.

Why is it difficult to state that one type of shopping bag is always more environmentally friendly?

The result depends on the full life cycle, manufacturing methods, transport, how often it is reused and how it is disposed of.

What does recycling mean?

Processing used materials so they can be made into new products.

How does recycling conserve finite resources?

It reduces the need to extract and process new raw materials.

How can recycling reduce energy use?

Processing recycled materials can require less energy than extracting and processing raw materials, although the amount saved depends on the material and process.

How can recycling reduce waste?

It diverts materials from landfill or other disposal routes and allows them to be used again.

Why is recycling metals useful?

Metal ores are finite, and extracting metals from ores can require large amounts of energy.

Why can recycling plastics be challenging?

Different polymers may need separating, and some plastics can be difficult to recycle or may lose quality during processing.

What is reuse?

Using a product again rather than throwing it away or processing it into a new material.

What is the difference between reuse and recycling?

Reuse uses the product again; recycling processes the material to make new products.

How can reducing, reusing and recycling help sustainability?

They reduce demand for new resources, reduce waste and may reduce energy use and environmental impacts.

Why is reducing resource use often helpful?

It avoids some of the extraction, manufacture, transport and disposal impacts associated with producing and using materials.