10.1 Global Reserves & Potable Water

In the UK, potable water is produced from fresh water.

Lakes and rivers are common sources of fresh water.

Name another source of fresh water.

Explain how drinking water is obtained from fresh water.

Pure water can be obtained from sea water by the process of distillation.

Explain why this is not used in the UK to produce drinking water.

Reverse osmosis is another method of desalination of fresh water which is a process that uses a membrane as shown in Figure 1.

Figure 1

Suggest what the role of the membrane is in reverse osmosis and why this is an expensive process.

Use Figure 1 to help you answer.

Potable water contains dissolved solids which are not harmful to drink in small quantities.

Describe a method that could be used to find out the amount of dissolved salts contained in different water samples.

A student investigated the amount of dissolved solids contained in different water samples.

They also measured the pH of the water samples.

Their results are shown in Table 1.

Table 1

What would you expect the pH and mass of dissolved solids to be in a sample of pure water?

Explain your answer.

How could the student confirm that the final water sample is pure?

Calculate the mass of the dissolved solids in 100 cm³ of sea water?

Use the results in Table 1.

Waste water, including sewage and agricultural waste water, requires treatment before being released into the environment.

Name two substances that must be removed from waste water prior to it being released.

Treatment of waste water produces liquid effluent and solid sewage sludge.

What two processes does waste water go through in order to produce the effluent and sludge?

How are the sewage sludge and liquid effluent treated?

Table 1 shows some information about how the treated solid sludge was disposed from one sewage treatment plant in 2000 and 2020.

Table 1

Calculate the percentage of treated solid sludge that was sent to landfill in 2000.

Give your answer to 3 significant figures.

The total mass of treated solid sludge increased from 2000 to 2020 and the proportions of how the sludge was disposed of changed.

Suggest one reason for the increase in the total mass of treated solid sludge and two reasons for the changes in the proportions of the disposal methods.

Use Table 1 to help you answer.

Copper is extracted from copper ores. The traditional method of extracting copper is by quarrying and then heating in a furnace.

In recent years, copper is being extracted from ores that contain a lower percentage of copper compounds.

Suggest two reasons why.

Bioleaching is a new method that can be used to extract copper from land that contains low percentages of copper compounds.

Bioleaching uses bacteria to produce copper sulfate solution.

Copper can be obtained from copper sulfate solution by electrolysis.

Give another method of how copper can be obtained from copper sulfate solution and explain why this method can extract copper from its compound.

Phytomining is another biological method to extract copper from low-grade copper ores.

Land where copper ore has been mined contains very low percentages of copper compounds.

Plants are grown on this land, absorbing the copper compounds through their roots.

The process of phytomining is shown in Figure 1.

Use the information in Figure 1 and your knowledge to evaluate the method of phytomining and the traditional method to extract copper.

Water from a local lake in the UK is used to provide drinking water to a local community.

The water requires treatment before being suitable for consumption.

What are the two main steps used to treat lake water?

In your answer provide a reason for each step.

Explain why producing drinking water from waste water is more complicated than it is to produce it from water in lakes.

Water that is safe to drink is called potable water.

Potable water is not pure water.

State the difference between potable water and pure water.

Some countries produce drinking water from sea water but this is a costly enterprise.

Explain why producing water from sea water is so expensive.

State how the water produced from sea water could be tested to show that it was pure.

Give the expected results if the water was pure.

A student used the following method to find out how much solid was dissolved in a sample of sea water:

• Measure the mass of an empty evaporating basin
• Measure 20 cm³ of the sea water sample using a measuring cylinder and pour into the evaporating basin
• Heat the evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the majority of water has evaporated
• Leave the basin until all of the water has evaporated
• Measure the mass of the cooled evaporating basin 

The results the student obtained are:

• Mass of empty evaporating basin = 21.35 g
• Mass of evaporating basin and dry solid residue = 21.96 g

Calculate the mass of solid dissolved in 1000 cm³ of the sea water.

This question is about the extraction and use of metals.

Many everyday domestic and industrial items are made from iron.

Haematite is an ore of iron and contains the compound iron oxide, Fe₂O₃.

Explain the meaning of the term ore.

Iron is produced by reacting Fe₂O₃ with carbon inside a blast furnace.

What type of reaction takes place?

The word equation for this reaction is:

iron oxide      +       carbon        →        iron    +    carbon dioxide

Complete and balance the symbol equation below.

___Fe₂O₃          +          ___C           →     __________   +      __________

Figure 1 shows the ways in which iron is extracted, used and recycled. 

Figure 1

Explain why the recycling of iron is necessary for sustainable development. 

This question is about alternative methods of extraction of copper.

Copper has many uses but is largely used in the production of electrical wiring.

Phytomining and bioleaching are alternative methods of extracting metals like copper.

Explain why alternative methods are necessary, commenting on how they affect the sustainability of extracting copper.

Phytomining is the technique used to obtain copper from areas of land that contain very low percentages of copper compounds.

Describe the process of phytomining.

Bioleaching is another technique used to extract copper from low grade ores.

Describe the process of bioleaching.

State one disadvantage of these alternative methods compared to the traditional methods of metal extraction.