Using the Earth’s Resources and Sustainable Development

1. What do humans use Earth’s resources for?

Answer: We use Earth’s resources for warmth, shelter, food and transport.

2. What are the Earth’s finite resources processed to provide?

Answer: Processed finite resources provide energy and materials.

3. What is "sustainable development" ?

Answer: Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.

4. What is "potable water" ?

Answer: Water that is safe to drink.

5. How can salty water be made into potable water?

Answer: Salty water can be made safe to drink by desalination, using techniques such as by distillation or reverse osmosis.

6. What should be removed from industrial waste water before it is released into the environment?

Answer: Industrial waste water must be treated to remove organic matter and harmful chemicals.

7. What is "bioleaching" ?

Answer: Bioleaching uses bacteria to produce leachate solutions that contain metal compounds.

8. Natural resources are found all around the world. They are used by humans to provide warmth, shelter, food and transport.

a) State a finite resource that is used as a fuel.

Answer: coal, oil, natural gas, fossil fuels

b) State a renewable resource used as a fuel.

Answer: wood, charcoal, biogas, biodiesel and bioethanol

c) Polyester is a synthetic fibre that can be used to make clothes. Give a natural product that polyester could replace.

Answer: Polyester could replace natural fibres such as cotton, silk or linen.

d) Aluminium metal is used to make drinks cans. Once they are used, they can be thrown away into landfill. Suggest how this metal can be used in a more sustainable way.

Answer: Recycle the metal and use the same metal again to make aluminium products.

e) Describe, with at least one example, the importance of chemistry in sustainable development.

Answer: Chemistry plays an important role in improving agricultural and industrial processes to provide new products, which could be focused on being sustainable. Some example are recycling metals, using biofuels, generate electricity from renewable energy sources, etc.

9. The figure below shows a pie chart that shows the sources of global energy.

a) Which renewable energy source contributes the least amount of global energy?

Answer: hydroelectric

b) Calculate the percentage of energy resources that are finite.

Answer: 33 + 27 + 21 = 81%

c) Calculate how many times greater the contribution of nuclear power to global energy is compared to hydroelectric power.

Answer: Three times greater.

d) Give the ratio of global energy for gas compared to nuclear.

Answer: 21:6 or 7:2

e) Use the figure above and your own knowledge to evaluate whether global energy sources are sustainable.

Answer: Sustainability is using resources to meet the needs of people today without preventing people in the future using them. Therefore, finite resources should be used responsibly as they can only be used once. Only 13% of energy is from renewable resources. The majority of the energy resources are fossil fuels which are finite. Therefore at the moment global energy use is not sustainable by the methods that we are using to generate the energy.

10. Safe, reliable drinking water is essential for humans and often water will need to be processed to make it safe to drink.

a) Describe the properties of drinking water.

Answer: Drinking water should have sufficiently low levels of dissolved salts and microbes.

b) Pure water is also potable water. But not all sources of potable water are pure. Explain the difference between potable water and pure water.

Answer: Potable water is safe to drink. Pure water only contains water molecules. Although pure water is potable other water is safe to drink and so potable. Tap water is a mixture (formulation) and is safe to drink, so is potable but as it contains other substances, it is not pure.

c) Describe and explain how potable water is produced in the UK.

Answer: Rain water/fresh water is collected from the ground, lakes or rivers, as it has low levels of dissolved substances. The water is passed through filter beds to remove insoluble substances and then sterilised/treated with chlorine/ozone/UV light to kill the microbes.

11. The table below shows the results of a student’s investigation of different water samples. Scientists sometimes use Kelvin (K) as the unit of temperature. To convert Kelvin to Celsius (°C) subtract 273.

a) Describe two ways the student could test the pH of the water sample.

Answer: use a pH probe or use universal indicator solution

b) Use the data in the table to justify the classification of each water sample as pure water or a mixture of water and other substances.

Answer: In pure samples, the boiling point is sharp, whereas mixtures boil over a range. So, the tap water and river water are both mixtures. Pure water will boil at exactly 100 °C which is 273K, and so the distilled water must be pure water.

c) Outline a method to determine which water sample had the greatest mass of dissolved solids.

Answer: Measure the mass of the water sample. Boil away (evaporate) all the water and take the mass of any residue. Calculate the percentage mass of the residue of each sample using (mass of residue ÷ mass of water × 100) and compare the values of the samples.

12. In the UK there are approximately 11 billion litres of waste water produced daily. The waste water is processed by 9000 sewage treatment works. It must be treated before it is released into streams and rivers.

a) State what is removed from sewage.

Answer: Sewage must have organic matter and harmful microbes removed.

b) List the contaminants that may be found in industrial waste water.

Answer: In industrial waste water there may be organic matter and harmful chemicals.

c) Describe how sewage is treated in the UK.

Answer: Waste water from the sewage system is screened and grit is removed. It then undergoes sedimentation to make sewage sludge and effluent. The sewage sludge goes to the anaerobic digestor and the effluent goes to the aerobic biological treatment.

d) Calculate, on average, how many litres of water are processed by each sewage treatment works. Give your answer in standard form and to two significant figures.

Answer: 11000000000 ÷ 9000 = 1222222 litres = 1.2 × 106 litres

13. The figure below shows copper demand by source. There are approximately 18 million metric tonnes of copper produced each year.

a) Use this information and your knowledge of structure and bonding to justify the main use of copper.

Answer: The main use of copper is electrical and electronic products. Copper is an electrical conductor, as there are free moving delocalised electrons that can carry the charge. Copper is also ductile and malleable, as the planes (layers) of atoms easily slide over each other allowing many different shapes and wires to be made.

b) Calculate the mass of copper used in transportation equipment each year. Give your answer to the nearest million metric tonnes.

Answer: (11.4 ÷ 100) × 18000000 = 2052000 = 2 million metric tonnes

c) Explain why we now extract copper from low grade copper ores.

Answer: Copper has a variety of uses and so we use large amounts of copper. As a result, high-grade copper ores have all been used and we now have to extract copper from low grade ores and copper ores are therefore becoming scarce.

d) Justify the use of phytomining for obtaining copper.

Answer: Uses lower grade ore and avoids traditional mining methods of digging, moving and disposing of large amounts of rock, which is better for the environment. It also uses less energy than traditional methods.

14. Copper ores are becoming more scarce. New technologies, such as bioleaching, allow lower grade ores to be used to obtain copper for electronics.

a) Describe the process of bioleaching.

Answer: Uses bacteria to produce leachate solutions (soluble metal solutions) that contain copper compounds.

b) Displacement can be used to extract copper metal from the leachate. Write a balanced symbol equation to show how scrap iron can be used to make copper from leachate containing copper(II) sulfate.

Answer: Fe + CuSO4  →  FeSO4 + Cu

c) Electrolysis can be used to extract the copper metal from the leachate. Write a half equation to show the production of copper. Include state symbols in your equation.

Answer: Cu2+(aq) + 2e  →  Cu(s)

d) Explain in terms of electrons, whether the copper in the leachate is being oxidised or reduced during these methods of extraction.

Answer: Copper ions in the leachate are being reduced, as electrons are being gained to form copper atoms.