Using Resources

Question 1

Describe the Difference Between Finite and Renewable Resources

Answer 1

-A finite resource will run out as the rate at which it is used is faster than the rate at which it is made.

-A renewable resource will not run out as the rate at which it is used is slower than the rate at which it is made.

Question 2

Explain what is Meant by Sustainable

Answer 2

To be sustainable, humans must be able to satisfy their needs in a way that does not prevent future generations from satisfying their needs.

Question 3

Describe the Difference Between Pure and Potable Water

Answer 3

-Potable water is water that is fit to drink.

-Pure water is water that contains no other additives.

Question 4

State Sources of Fresh Water

Answer 4

-Porous underground rocks (aquifers).

-Rainwater falling to the ground and collecting as surface water (replenishing freshwater in rivers and lakes).

Question 5

Describe the Process of Making Potable Water from Fresh Water

Answer 5

-Choose an appropriate source of fresh water, such as rivers, streams, lakes and boreholes.

-Grated bars or a wire mesh are used to screen out large objects. To remove sand and soil, the water is allowed to sit in a settlement tank.

-To remove smaller particles of dirt, chemicals are added to aggregate the smaller particles so they also settle out.

-To remove smaller particles of mud and grit, the water is passed through a microfilter. Undissolved particles are also passed through filter beds.

-To remove harmful bacteria, the water is sterilised by adding chlorine, ozone or UV light. To change the pH, add acid if greater than 7 or add alkali if less than 7.

Question 6

Describe the Processes of Making Potable Water from Seawater

Answer 6

-In reverse osmosis, the sea water is passed through a series of filters or membranes which gradually reduce the levels of dissolved minerals.

-In distillation, the seawater is heated to evaporate the water (leaving the minerals behind). The pure water vapour is then condensed back to liquid water and collected.

Question 7

Describe the Disadvantages of Distillation and Reverse Osmosis

Answer 7

-Both reverse osmosis and distillation use large amounts of energy. This makes them extremely expensive.

-Reverse osmosis involves an expensive membrane which needs replacing.

-Distillation is a batch process.

Question 8

Describe a Method for Analysing a Water Sample

Answer 8

-First, check the pH of the water sample by adding a drop of water to a piece of universal indicator paper. Then, use a balance to to find the mass of an empty evaporating basin.

-Pour 10 cm3 of the water sample into the evaporating basin.

-Heat the evaporating basin on a tripod and gauze using a Bunsen burner until solids start to form and the water has evaporated.

-Remove the sample from heat and once cool, weigh the evaporating basin again and calculate the mass of the solids that was dissolved in the water.

Question 9

Explain why pH 7 Does Not Show that the Water Sample is Pure

Answer 9

-Pure water does have a pH of 7. However, pure water also must contain no dissolved substances.

-It is possible for a sample of water to have a pH of 7 but still to contain dissolved substances. This would not be pure water.

Question 10

Explain how the Results of Analysing a Water Sample Will Show that it is Pure

Answer 10

-If the water sample is pure then the final mass of the empty evaporating basin (after heating) will be the same as the initial mass of the empty evaporating basin (before heating).

-This shows that the water contained no dissolved salts.

-If the water had contained dissolved salts, they would have been left after the water evaporated.

-This would have meant that the mass of the empty evaporating basin was greater after heating than before.

Question 11

State Causes of Anomalous Results when Analysing a Water Sample

Answer 11

-If the mass is too large, the sample has not been heated to constant mass. The evaporating basin may also contain condensation underneath.

-If the mass is too small, the evaporating basin may not have been clean at the start. There may have also been solid lost during transfer from heat to mass.

Question 12

Describe a Method for Purifying a Sample of Water

Answer 12

-Place the water sample in the conical flask. Set up the apparatus for distillation as shown in the diagram.

-Heat the water using the Bunsen burner until it boils. Then reduce the heat so that the water boils gently.

-The distilled water will collect in the cooled test tube. Collect about 1 cm depth of water in this way, then stop heating.

-Analyse the distilled water by determining its boiling point. Pure water should have a boiling point of 100ºC.

Question 13

Explain why Iced Water is Used when Purifying a Sample of Water

Answer 13

The purpose of the iced water is to cool the test tube down so that the water vapour condenses.

Question 14

Explain why Waste Water can not be Returned Directly Back to Rivers

Answer 14

-Waste water from homes and farms contains a great deal of harmful microorganisms and organic molecules.

-Returning this untreated waste water to rivers would be
extremely dangerous to aquatic organisms such as fish.

-Bacteria in the river would feed on the organic molecules. The bacteria would reproduce and before long there would be a huge number of bacteria.

-These bacteria would use all of the oxygen in the water. Lack of oxygen would cause other organisms to die.

Question 15

Describe the Treatment of Waste Water

Answer 15

-The sewage is screened- this involves passing the water through fine metal meshes. These filter out solids and grit.

-Then, its allowed to stand in a settlement tank and undergoes sedimentation- the heavier suspended solids sink to the bottom to produce sludge while the lighter effluent floats to the top.

-The effluent is removed and treated by biological aerobic digestion. Air is pumped through the water to encourage aerobic bacteria to break down organic matter.

-The sludge is removed and treated by anaerobic digestion. This produces methane gas which can be used as an energy source and remaining digested waste as fertiliser or biofuel.

-Water can be further treated by adding chlorine, ozone or using UV light before being returned to waterways.

Question 16

Describe the Difference Between High Grade and Low Grade Ores

Answer 16

-An ore is a rock containing enough of a metal to be economically viable to extract a metal from it.

-High grade ores have a higher percentage of the desired metal.

-Low grade ores are only just economically viable, or only viable with new methods.

Question 17

Describe the Process of Smelting (Carbon Reduction)

Answer 17

-Smelting is used for high grade ores.

-It involves using carbon and a high temperature to displace a less reactive metal.

Question 18

Describe the Advantages and Disadvantages of Smelting

Answer 18

Advantage:
-Charcoal is cheap

Disadvantages:
-Forms carbon dioxide (a greenhouse gas)
-Uses a high temperature which needs a lot of energy so is expensive.

Question 19

Describe the Process of Displacement

Answer 19

-Displacement is used for high grade ores.

-It involves a more reactive metal taking the place of a less reactive metal that is already bonded in a compound.

Question 20

Describe the Advantages and Disadvantages of Displacement

Answer 20

Advantage:
-Scrap iron can be used

Disadvantage:
-More expensive reactive metals have to be used

Question 21

Describe the Process of Electrolysis

Answer 21

-Electrolysis is used for high grade ores.

-It involves using electricity to split a compound into its elements.

Question 22

Describe the Advantages and Disadvantages of Displacement

Answer 22

Advantages:
-Produces the highest purity of metal
-Works on the most reactive metals

Disadvantage:
-Lots of energy is needed so is expensive

Question 23

Describe the Process of Phytomining

Answer 23

-Phytomining is used for low grade ores.

-It involves growing plants on land containing copper ores. They absorb the copper but can’t use or get rid of it so it builds up in the leaves.

-The plants are then burnt to produce ash. This leaves behind copper. The ash is also dissolved in acid to produce a solution of a copper compound.

-Copper can then be extracted from the solution by electrolysis or displacement with a more reactive metal. e.g scrap iron.

Question 24

Describe the Advantages and Disadvantages of Phytomining

Answer 24

Advantage:
-It is a carbon neutral process- it takes in carbon dioxide when the plants are growing and releases it when the plants are burnt

Disadvantages:
-It is time consuming so inefficient
-There are additional environmental impacts from farming the land such as carbon dioxide produced by burning fuels to drive tractors

Question 25

Describe the Process of Bioleaching

Answer 25

-Bioleaching is used for low grade ores. -It involves bacteria converting copper compounds in the chosen ore into soluble copper compounds, separating out the copper from the ore in the process. -The ore is sprayed with the bacteria. Time is then allowed for chemical reactions to take place. The bacteria then produce leachate. -This contains copper ions which can be extracted by electrolysis or displacement with a more reactive metal. e.g scrap iron.

Question 26

Describe the Advantages and Disadvantages of Bioleaching

Answer 26

Advantage: -Can be carried out over large areas without the need for intervention Disadvantage: -Bacteria often produce sulfur which reacts to form sulfur dioxide and contributes to acid rain.

Question 27

Describe the Difference Between Reuse and Recycle

Answer 27

Reuse- using the same materials again for the same process. Recycle-using the materials for a different purpose.

Question 28

Describe the Consideration of Extracting the Raw Materials in a Life Cycle Assessment

Answer 28

-Extracting raw materials needed for a product can damage the local environment. -Raw materials often have to be processed to extract the desired materials and this often needs large amounts of energy. -Consideration must also be taken over whether the material is finite or renewable.

Question 29

Describe the Consideration of Making the Product in a Life Cycle Assessment

Answer 29

-Manufacturing products and their packaging can use a lot of energy. -Waste products must also be considered such as the amount of carbon dioxide produced as these can cause pollution. Consideration must also be taken over the number of processing steps.

Question 30

Describe the Consideration of Using the Product in a Life Cycle Assessment

Answer 30

-How long a product is used for or how many years it gets without needing to be replaced is an important factor. -The use of a product can also damage the environment for example driving cars involves burning fossil fuels.

Question 31

Describe the Consideration of Disposing the Product in a Life Cycle Assessment

Answer 31

-A product that can be recycled will be more environmentally friendly than a product that cannot. -A product that is non-toxic and biodegradable is also beneficial.

Question 32

Describe the Problems with Life Cycle Assessments

Answer 32

-It can be very difficult to accurately work out the environmental impact of different processes so sometimes we have to make estimates. -Also, lifecycle assessments may be biased, for example to make a product look less harmful to the environment than it actually is.

Question 33

Describe the Difference Between Corrosion and Rusting

Answer 33

-Corrosion is the destruction of a material by chemical reactions in the environment. -Rusting is the corrosion of iron involving the reaction with both water and oxygen. Iron + Oxygen + Water → Hydrated Iron (III) Oxide

Question 34

Describe a Reaction Between Iron and Oxygen

Answer 34

-Place calcium chloride and a iron nail into a test tube. Place a bung on top. -This tests for the reaction between iron and oxygen. -Calcium chloride absorbs moisture from inside the test tube. The bung also prevents any more air from entering the test tube. -There will be no change observed because rusting cannot take place as there is no water in the reaction.

Question 35

Describe a Reaction Between Iron and Oxygen and Water

Answer 35

-Pour distilled water into a test tube so that it is not completely filled. This leaves a space of air. -This tests for the reaction between iron, oxygen and water (rusting). -An orange layer will form around the nail as both oxygen and water are present so rusting can take place. Hydrated iron (III)oxide is formed.

Question 36

Describe a Reaction Between Iron and Water

Answer 36

-Pour boiled water into a test tube so that it is almost full. Fill the rest of the space with a layer of oil. -This tests for the reaction between iron and water. -The layer of oil prevents oxygen from dissolving in the water or entering the test tube. -There will be no change observed because rusting cannot take place as there is no oxygen in the reaction.

Question 37

Describe how Barrier Methods Work to Prevent Rust

Answer 37

-Barrier methods provide a layer that stops oxygen or water (or other corrosive materials) reaching the item that you wish to protect e.g. paint it or cover it in grease. -Electroplating is another example of a barrier method. It is a way of applying a thin layer of metal on the surface of another metal, using electrolysis.

Question 38

Explain why Aluminium Does Not Need Protection from Corrosion

Answer 38

-Aluminium is quite a reactive metal. This means that the surface of aluminium reacts with oxygen in the air. -However, the thin layer of aluminium oxide produced now protects the rest of the aluminium underneath from corrosion.

Question 39

Describe how Sacrificial Protection Works to Prevent Rust

Answer 39

-Sacrificial protection involves adding a more reactive metal so that it reacts instead of the object being protected. -Galvanisation is an example of sacrificial protection. It involves coating an iron object in a layer of zinc. As zinc is more reactive, it will react instead of iron.

Question 40

Explain why Alloys are Harder than Pure Metals

Answer 40

-Alloys are a mixture of different sized atoms. -This means the layers become distorted. -This means the layers can't slide over each other. -Therefore, alloys are harder than pure metals.

Question 41

Describe the Properties of Bronze

Answer 41

-Bronze is an alloy of copper and tin. -It is resistant to corrosion and tough. -The resistance to corrosion protects it against the weather. -Often used for statues.

Question 42

Describe the Properties of Brass

Answer 42

-Brass is an alloy of copper and zinc. -Harder than pure copper. -The hardness makes them robust. -Often used as doorhandles.

Question 43

Describe the Properties of Gold

Answer 43

-Gold is an alloy of gold, copper, silver and zinc. -The alloy is harder than the element and comes in different colours. -Its properties make it pretty and resistant to corrosion. -Often used in jewellery.

Question 44

Describe the Properties of Low Carbon Steel

Answer 44

-Low carbon steel is an alloy of iron and 0.05 to 0.309% carbon. -It is soft enough to easily shape. -It does not shatter on impact. -Often used for car bodies.

Question 45

Describe the Properties of High Carbon Steel

Answer 45

-High carbon steel is an alloy of iron and 0.8 to 2.0% carbon. -It is extremely hard. -It is also brittle. -Often used to make cutting tools.

Question 46

Describe the Properties of Stainless Steel

Answer 46

-Stainless steel is an alloy of iron with chromium and nickel. -It is resistant to corrosion. -The resistance to corrosion protects it form the weather. -It is used to make cutlery.

Question 47

Describe the Properties of Aluminium

Answer 47

-Aluminium is an alloy of aluminium and other metals (e.g. titanium). -It is low density, strong and resistant to corrosion. -It is used to make aircraft.

Question 48

Describe the Haber Process

Answer 48

-The Haber Process is used to manufacture ammonia, which can be used to produce nitrogen-based fertilisers. -On cooling, the ammonia condenses and is removed. By removing the ammonia from the reaction, the equilibrium shifts to the right, which increases the yield -The remaining hydrogen and nitrogen are recycled and returned to the reaction vessel via the compressor. -Recirculating the unreacted nitrogen and hydrogen back over the catalyst increases the yield by giving the molecules more chance to react together.

Question 49

Describe the Materials and Conditions Used in the Haber Process

Answer 49

-The Haber Process uses nitrogen (from the air) and hydrogen (from natural gases such as methane). -It takes place at 450℃ (compromise of temperature), 200 atmospheres of pressure (compromise of pressure) and uses an iron catalyst.

Question 50

Explain why the Temperature Chosen for the Haber Process is a Compromise

Answer 50

-A high temperature increases the rate of reaction because particles have more energy so there are more frequent collisions with energy greater than than activation energy. -However, the forward reaction is exothermic so decreasing the temperature shifts the position of equilibrium to the right to increase the yield. -Therefore, a compromise in temperature is needed.

Question 51

Explain why the Pressure Chosen for the Haber Process is a Compromise

Answer 51

-A high temperature increases the rate of reaction because there are more particles in a given volume so there are more frequent collisions with energy greater than than activation energy -There are also more moles of gas on the left so increasing pressure shifts the position of equilibrium to the right to increase the yield. -However, a compromise is still needed because a high pressure is expensive and dangerous (explosions).

Question 52

Explain why an Iron Catalyst is Used in the Haber Process

Answer 52

-The catalyst increases the rate of reaction without being used up because it provides an alternative pathway with lower activation energy. -Catalysts have no effect on the position of equilibrium.

Question 53

Describe NPK Fertilisers

Answer 53

-NPK fertilisers contain formulations of compounds, containing three 'macro nutrients'- Nitrogen, Phosphorous and Potassium. -Fertilisers improve agricultural productivity because they make crops grow larger and faster.

Question 54

Describe the Differences Between Making Fertilisers in the Lab to Making it on an Industrial Scale

Answer 54

-Lab fertiliser is made on a small scale whereas industry fertiliser is produced on a larger scale. -It is safer to make fertiliser in the lab than on an industrial scale. -Lab fertiliser is made using glass equipment whereas industry fertiliser is made using stainless steel equipment. -lab fertiliser is made at room temperature and atmospheric pressure whereas in industry, a much higher pressure and temperature is used. -Lab fertiliser is made in a batch process whereas industry fertiliser is made in a continuous process.

Question 55

Describe the Production of Soluble Phosphates

Answer 55

-Phosphate rock is mined from the ground. The phosphate salts in the rocks are insoluble so plants can't use them as nutrients. They are reacted with acid to make soluble phosphates. -Reacting phosphate rock with nitric acid produces phosphoric acid and calcium nitrate. -Phosphoric acid is a strong acid and would be extremely damaging to crops. It needs to be converted to a neutral compound (ammonium phosphate). -Reacting phosphate rock with sulfuric acid produces calcium sulfate and calcium phosphate (single superphosphates). -Reacting phosphate rock with phosphoric acid only produces calcium phosphate (triple superphosphate)

Question 56

Describe the Difference Between Ceramics and Composites

Answer 56

-Ceramics are non-metal solids with a high melting point that are not made from carbon based compounds. -Composites are made of one material embedded in another. Fragments of a material (reinforcement) are surrounded by a matrix acting as a binder.

Question 57

Describe the Properties of Clay

Answer 57

-Clay is a soft material when dug out of the ground so can be moulded into different shapes. When its fired at high temperatures, it hardens to form a clay ceramic. -Its ability to be moulded when wet and then harden makes clay ideal for making pottery and bricks. -It is malleable when wet because the layers slide over each other. -When heated it is brittle because heating removes water molecules which forms perfectly straight layers. Cracks then form between the layers.

Question 58

Describe the Properties of Soda Lime Glass

Answer 58

-It is made by mixing sand, sodium carbonate and limestone. It is then heated to melt, shaped and cooled. -Soda lime glass has a high melting point. -It is used to make everyday glass items such as windows and glass bottles

Question 59

Describe the Properties of Borosilicate Glass

Answer 59

-It is made by mixing sand and boron trioxide. It is then heated to melt, shaped and cooled. -Borosilicate glass has a higher melting point than soda lime glass so will not melt when heated. It is also stronger and less likely to shatter. -It is used to make lab equipment )test tubes) and measuring equipment.

Question 60

Describe the Properties of Different Composites

Answer 60

-Concrete is made from aggregate (a mixture of sand and gravel) embedded in cement. This makes it very string so is used as a building material. -Fibreglass consists of fibres of glass embedded in matrix made of polymer (plastic). It has a low density but is very strong. It is used to make skis, bots and surfboards. -Carbon fibre composites also have a polymer matrix. the reinforcement is made from chains of carbon atoms bonded together or from carbon nanotubes. -These composites are strong and light so are used to make car and aircraft parts.

Question 61

Describe Thermosetting Polymers

Answer 61

-Thermosetting polymers do not melt when heated. -This is because the polymer strands are held to each other by strong crosslinks (usually covalent bonds). These are so strong that they are not broken by heat.

Question 62

Describe Thermosoftening Polymers

Answer 62

-Thermosoftening polymers melt/soften at high temperatures. They can be moulded and keep their new shape when cooled. -The polymer strands are held to each other by weak intermolecular forces of attraction only. -If the polymer is heated, these intermolecular forces of attraction are weakened or broken. This allows the polymer strands to move away from each other and the polymer loses its structure. -If the polymer is cooled, the intermolecular forces of attraction reform. This means that the polymer now reforms into a solid.

Question 63

Describe Low Density Polyethene

Answer 63

-Consists of branched chains. These prevent the chains getting too close so there is a lot of space between them. -It is made by addition polymerisation of ethene using high pressure and a trace of oxygen. -It is flexible so used for bags.

Question 64

Describe High Density Polyethene

Answer 64

-Consists of linear chains. There is very little space between chains so it is very dense. -It is made by addition polymerisation of ethene at 50℃ with a catalyst. -It is rigid at room temperature so used for water tanks and drainpipes.