CGP 10

Question 1

What are ceramics

Answer 1

. Ceramics are non-metal solids with high melting points that aren’t made from carbon-based compounds

Question 2

Clay

Answer 2

. Some ceramics can be made form clay
. Clay is soft so it can be molded into different shapes
. When it’s fired at high temperatures, it hardens to form a clay ceramic
. It’s ability to be molded when wet and then hardened makes clay ideal for making pottery and bricks

Question 3

Glass

Answer 3

. Another example of a ceramic is glass. Glass is generally transparent, can be molded when hot and brittle when thin

. Most glass is made from soda-lime glass, which is made by heating a mixture of limestone, sand and sodium carbonate (soda) until it melts.

. Borosilicate glass has a higher melting point than soda-lime glass. It’s made in the same way as soda-lime glass, using a mixture of sand and boron-trioxide

Question 4

What are composites

Answer 4

. Composites are made of one material embedded in another. Fibers or fragments of a material (known as reinforcement) are surrounded by a matrix acting as a binder. The properties of a composite depend on the properties of the materials it’s made from.

Question 5

What are examples of composites

Answer 5

. Fiberglass
. Carbon fibre
. Concrete
. Wood

Question 6

Fiberglass

Answer 6

. Fiberglass consists of fibers of glass embedded in a matrix of polymer (plastic). It has a low density (like plastic) but is very strong(like glass).

Question 7

Carbon fiber

Answer 7

. Carbon fiber composites also have a polymer matrix. The reinforcement is made from long chains of carbon atoms bonded together (carbon fibers) or from carbon nanotubes.

. These composites are very strong and light so are used in aerospace and sports car manufacturing

Question 8

Concrete

Answer 8

. Concrete is made from aggregate ( a mixture of sand and gravel) embedded in cement. It’s very strong. This makes it ideal for use as a building material, e.g. in skate parks

Question 9

Wood

Answer 9

Wood is a natural composite of cellulose fibers held together by an organic polymer matrix

Question 10

How can the type of catalyst used and the present reaction conditions influence the properties of a polymer

Answer 10

The properties of poly(ethene) depend on the catalyst used and the reaction conditions

. Low density poly(ethene) is made from ethene at a moderate temperature under a high pressure and with a catalyst. It’s flexible and used for big bags and bottles

. High density poly(ethene) is made from ethene but at a lower temperature and pressure with a different catalyst. It’s more rigid and is used for water tanks and drainpipes

Question 11

The monomers that a polymer is made from determine the type of bonds that form between the polymer chains. These weak bonds between the different molecules determine the properties of the polymer:

Answer 11

. Thermosoftening polymers contain individual polymer chains entwined together with weak forces between the chains. You can melt these plastics and remould them.

. Thermosetting polymers contain monomers that can form cross-links between the polymer chains. holding the chains together in a solid structure. Unlike Thermosoftening polymers, these polymers don’t soften when heated. Thermosetting polymers are strong, hard and rigid

Question 12

Ceramics

Answer 12

. Ceramics include glass and clay ceramics such as porcelain and bricks. They’re insulators of heat and electricity, brittle (they aren’t very flexible and break easily) and stiff

Question 13

Polymers

Answer 13

. Polymers are insulators of heat and electricity, they can be flexible (they can be bent without breaking) and are easily moulded. Polymers have many applications including in clothing and

Question 13

Polymers

Answer 13

. Polymers are insulators of heat and electricity, they can be flexible (they can be bent without breaking) and are easily moulded. Polymers have many applications including in clothing and insulators in electrical items

Question 14

Composites

Answer 14

The properties of composites depend on the matrix/binder and the reinforcement used to make them, so they have many different uses

Question 15

Metals

Answer 15

. Metals are malleable, good conductors of heat and electricity, ductile (can be drawn into wires), shiny and stiff.

Question 16

How are alloys made

Answer 16

. Alloys are made by adding another element to the metal. This disrupts the structure of the metal, making alloys harder than pure metals

Question 17

Corrosion

Answer 17

. Corrosion is where metals react with substances in their environment and are gradually destroyed
. Corrosion only happens on the surface of a material where it’s exposed to the air

Question 18

Iron corrosion

Answer 18

. Iron corrodes easily (rusts).
. Rust is only used for iron corrosion, not other elements
. In order to rust, iron needs to be in contact with both oxygen and water which are present in the air
. Unfortunately, rust is soft and crumbly and flakes off to leave more iron available to rust away

Question 19

Rust

Answer 19

. The stuff we call rust is actually the compound hydrated iron (III) oxide.

iron + oxygen + water = hydrated iron (III) oxide

Question 20

Aluminium corrosion

Answer 20

. Aluminium corrodes when exposed to air. Unlike iron objects, things made from aluminium aren’t completely destroyed by corrosion. This is because aluminium oxide that forms when aluminium corrodes doesn’t flake away. In fact, it forms a nice protective layer that sticks firmly to the aluminium below and stops any further reaction taking place

Question 21

Experiment to show that both water and air are needed for corrosion

Answer 21

. If you put an iron nail in a test tube of just water (water is boiled to remove air, oil is used to prevent air entering), it won’t rust
. If you put an iron nail in a test tube of just air (calcium chloride is used to absorb any water from the air), it won’t rust
. If you put an iron nail in a test tube of water and air, it will rust

Question 22

What are the two main ways to prevent rusting

Answer 22

. Coating the iron with a barrier
. Sacrificial method

Question 23

Coating iron with a barrier

Answer 23

You can coat the iron with a barrier to keep out the water and oxygen, this can be done by:
. Painting/ Coating with plastic - ideal for big and small structures alike. It can be decorative too
. Electroplating - This uses electrolysis to reduce metal ions onto an iron electrode. It can be used to coat the iron with a layer of a different metal that won’t be corroded away
. Oiling/ Greasing - This has to be used when moving parts are involved, like on bike chains

Question 24

Sacrificial method

Answer 24

. Another method is the sacrificial method. This involves placing a more reactive metal such as zinc or magnesium with the iron. Water and oxygen then react with the sacrificial metal instead of the iron

Question 25

Protective techniques using both

Answer 25

Some protection techniques employ both methods above. For example:
. An object can be galvanised by spraying it with a coating of zinc. The zinc layer is firstly protective, but if it’s scratched, the zinc around the site of the scratch works as a sacrificial metal

Question 26

Natural resources

Answer 26

. Natural resources form without human input. They include anything that comes from the earth, sea or air. For example, cotton for clothing or oil for fuel

. Some of these natural products can be replaced by synthetic products or improved by man-made processes. For example, rubber is a natural product that can be extracted from the sap of a tree, however man-made polymers have now been made which can replace rubber in uses such as tyres

. Agriculture provides conditions where natural resources can be enhanced for our needs. E.g. The development of fertilisers meant that we can produce a high yeald of crops

Question 27

Renewable resources lifetime

Answer 27

. Renewable resources reform at a similar rate to, or faster than, we use them
. For example, timber is a renewable resource as trees can be planted following a harvest and only take a few years to grow. Other examples of renewable resources include fresh water and food

Question 28

lin tFinite rescources lifetime

Answer 28

. Finite resources, aren’t formed quickly enough to be considered replaceable

. Finite resources include fossil fuels and nuclear fuels such as uranium and plutonium. Minerals and metals found in ores in the earth are also non-renewable resources

. After they’ve been extracted, they undergo man-made processes to provide fuels and materials necessary for modern life. For example, fractional distillation is used to produce usable products such as petrol from crude oil and metal ores are reduced to produce a pure metal

Question 29

Risks of extracting

Answer 29

. Many modern materials are made from raw, finite resources, for example most plastics, metals and building materials.
. People have to balance the social, economic and environmental effects of extracting finite resources.

. For example, mining metal ores is good because useful products can be made. It also provides local people with jobs and brings money into the area. However, mining ores is bad for the environment as it uses loads of energy, scars the landscape, produces lots of waste and destroys habitats

Question 30

What is sustainable development

Answer 30

. Sustainable development is an approach to development that takes account of the needs of present society while not damaging the lives of future generations.

. One way of reducing the use of finite resources is using less. This doesn’t just reduce the use of the resource but also anything needed to produce it

. We can’t stop using finite resources altogether, but chemists can develop and adapt processes that use lower amounts of finite resources and reduce damage to the environment. for example, chemists have developed catalysts that reduce the amount of energy needed for certain industrial processes

Question 31

Extracting resources

Answer 31

. Extracting resources can be unsustainable due to the amount of energy used and waste produced. Processing the resources into useful materials, such as glass or bricks, can be unsustainable too, as the processes often use energy that’s made from finite resources.

Question 32

Copper

Answer 32

. Copper is a finite resource, one way to improve its sustainability is by extracting it from low grade ores (ores without much copper in). Scientists are looking into new ways of doing this:
. Bioleaching
. Phytomining

Question 33

. Bioleaching

Answer 33

. Bacteria are used to convert copper compounds in the ore into soluble copper compounds, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper ions, which can be extracted e.g. by electrolytes or displacement with a more reactive metal

Question 34

Phytomining

Answer 34

. This involves growing plants in soil that contains copper. The plants can’t use or get rid of the copper so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement using scrap iron.

Question 35

Traditional method of copper mining

Answer 35

. Traditional methods of copper mining are pretty damaging to the environment. These new methods of extraction have a much smaller impact, but the disadvantage is that they’re slow

Question 36

metals

Answer 36

. Mining and extracting metals takes a lot of energy which comes from burning fossil fuels
. Recycling metals often uses much less energy than is needed to mine and extract a new metal, conserves the finite amount of each metal in the earth and cuts down on the amount of waste getting sent to landfill

Question 37

Recycling metals

Answer 37

. Metals are usually recycled by melting them and then casting them into the shape of a new product

. Depending on what the metal will be used for after recycling, the amount of separation required for recyclable metals can change. For example, waste steel and iron can be kept together as they can both be added to iron in a blast furnace to reduce the amount of iron ore required

Question 38

Glass recycling

Answer 38

Glass recycling can also help sustainability by reducing the amount of energy needed to make new glass products, and also the amount of waste created when used glass is thrown away
. Glass bottles can often be reused without reshaping
. Other forms of glass can’t be reused so they’re recycled instead. Usually the glass is separated by color and chemical composition before being recycled
. The glass is crushed and then melted to be reshaped for use in glass products such as bottles or jars. It might also be used for a different purpose such as insulating glass wool for wall insulation in homes

Question 39

Life cycle assessments

Answer 39

. If a company wants to manufacture a new product, they carry out a life cycle assessment
. A life cycle assessment (LCA) looks at every stage of a products life to assess the impact it would have on the environment
It is split up into three parts:
. Getting the raw materials
. Manufacture and packaging
. Using the product
. Product disposal

Question 40

Getting the raw materials

Answer 40

. Extracting the raw materials needed for a product can damage the local environment, e.g. mining metals. Extraction can also result in pollution due to the amount of energy needed

. Raw materials often need to be processed to extract the desired materials and this often needs large amounts of energy. E.g. extracting metals from ores or fractional distillation of crude oil

Question 41

Manufacture and packaging

Answer 41

. Manufacturing products and their packaging can use a lot of energy resources and can also cause a lot of pollution e.g. harmful fumes such as carbon monoxide or hydrogen chloride

. You also need to think about any waste products and how to dispose of them. The chemical reactions used to make compounds from their raw materials can produce waste products. Some waste can be turned into other useful chemicals, reducing the amount that ends up in the environment

Question 42

Manufacture and packaging

Answer 42

. Manufacturing products and their packaging can use a lot of energy resources and can also cause a lot of pollution e.g. harmful fumes such as carbon monoxide or hydrogen chloride

. You also need to think about any waste products and how to dispose of them. The chemical reactions used to make compounds from their raw materials can produce waste products. Some waste can be turned into other useful chemicals, reducing the amount that ends up in the environment.

Question 43

Using the product

Answer 43

. The use of a product can damage the environment. For example burning fuels releases greenhouse gases and other harmful substances. Fertilisers can leach into streams and rivers causing damage to ecosystems

. How long a product is used for or how many uses it gets is also a factor - products that need lots of energy to produce but are used for ages mean less waste in the long run

Question 44

Product disposal

Answer 44

. Products are often disposed of in landfill sites.This takes up space and pollutes land and water, e.g. of paint washes off a product and gets into rivers
. Energy is used to transport waste to landfill, which causes pollutants to be released into the atmosphere
. Products might be incinerated (burnt). which causes air pollution

Question 45

Problems with life cycle assessments

Answer 45

. The use of energy, some natural resources and the amount of certain types of waste produced by a produce over it’s lifetime can be easily quantified. But the effect of some pollutants is harder to give a numerical value to. E.g. it’s difficult to apply a value to the negative visual effects of plastic bags in the environment compared to paper ones
. So producing an LCA is not an objective method as it takes into account the values of the person carrying out the assessment. This means LCAs can be biased

Question 46

Problems with life cycle assessments

Answer 46

. The use of energy, some natural resources and the amount of certain types of waste produced by a produce over it’s lifetime can be easily quantified. But the effect of some pollutants is harder to give a numerical value to. E.g. it’s difficult to apply a value to the negative visual effects of plastic bags in the environment compared to paper ones
. So producing an LCA is not an objective method as it takes into account the values of the person carrying out the assessment. This means LCAs can be biased.

Question 47

Selective LCA’s

Answer 47

Selective LCA’s which only show some of the impacts of a product can also be biased as they can be written to deliberately support the claims of a company, in order to give them positive advertising

Question 48

Potable water

Answer 48

. Potable water is water that has been treated or is naturally safe for humans to drink
. It isn’t pure though, pure water ONLY contains H2O molecules
. The important thing is that the levels of dissolved salts aren’t too high, that it has a pH between 6.5 and 8.5 and also that there aren’t any nasties (like bacteria or other microbes) swimming around in it

Question 49

Potable water depending on where you are

Answer 49

. Rainwater is a type of fresh water. Fresh water is water that doesn’t have much dissolved in it
. When it rains, water can either collect as surface water (in lakes, rivers and reservoirs) or as groundwater (in rocks such as aquifers)

Question 50

Fresh water in the Uk

Answer 50

. In the UK the source of freshwater used depends on location. Surface water tends to dry up first, so in warm areas e.g. the south-east, most of the domestic water supply comes from groundwater

Question 51

How does potable water become safe to drink

Answer 51

. Even though it has low levels of dissolved substances, water from these fresh water sources still needs to be treated to make it safe before it can be used. This process includes:
. Filtration - a wire mesh screens out large twigs etc, and then gravel and sand beds filter out any solid bits
. Sterilisation - the water is sterilised to kill any harmful bacteria or microbes. This can be done by bubbling chlorine gas through it or by using ozone or ultraviolet light

Question 52

In some dry countries e.g Kuwait, there’s not enough surface or groundwater and instead sea water must be treated by distillation to provide potable water. Distillation can be used to desalinate sea water, here’s how you can test and distil water in the lab

Answer 52

. First, test the pH of the water using a pH meter. If the pH is too high or too low, you’ll need to neutralise it. You can do this with a titration, but use a pH meter to tell you when the solution’s neutral, rather than an indicator, as this won’t contaminate the water

.

Question 53

In some dry countries e.g Kuwait, there’s not enough surface or groundwater and instead sea water must be treated by distillation to provide potable water. Distillation can be used to desalinate sea water, here’s how you can test and distil water in the lab

Answer 53

. First, test the pH of the water using a pH meter. If the pH is too high or too low, you’ll need to neutralise it. You can do this with a titration, but use a pH meter to tell you when the solution’s neutral, rather than an indicator, as this won’t contaminate the water

.Rem

Question 54

Reminder

Answer 54

Distillation practical

Question 55

Reverse osmosis

Answer 55

. Sea water can also be treated by processes that use membranes - like reverse osmosis. The salty water is passed through a membrane that only allows water molecules to pass through. Ions and larger molecules are trapped by the membrane so they are separated by the water

Question 56

Why is distillation and reverse osmosis not practical

Answer 56

. Both distillation and reverse osmosis need lots of energy, so they’re really expensive and not practical for producing large quantities of fresh water

Question 57

Waste water sources

Answer 57

. Domestic waste can come from things like having a bath, flushing the toilet etc.
. Agricultural systems also produce a lot of waste water including nutrient run-off from fields and slurry from animal farms
.

Question 58

Waste water sources

Answer 58

. Domestic waste can come from things like having a bath, flushing the toilet etc.
. Agricultural systems also produce a lot of waste water including nutrient run-off from fields and slurry from animal farms

Question 59

What is the process of treating waste water

Answer 59

. Before being treated, the water is screened - this involves removing any large bits of material (like twigs or plastic bags) as well as any grit
. Then it’s 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 on the top
. Th effluent in the settlement tank is removed and treated by biological aerobic digestion. This is when air is pumped through the water to encourage aerobic bacteria to break down any organic matter - including other microbes in the water
. The sludge from the bottom of the settlement tank is also removed and transferred to into large tanks. Here it gets broken down by bacteria in a process called aerobic digestion
. Anaerobic digestion breaks down the organic matter in the sludge, releasing methane gas in the process. The methane gas can be used as energy source and the remaining digested waste can be used as a fertiliser
. For waste water including toxic substances, additional stages of treatment may involve adding chemicals (e.g. to precipitate metals), UV radiation or using membranes

Question 60

Sewage treatement

Answer 60

. Sewage treatment requires more processes than treating fresh water but uses less energy than the desalination of salt water, so could be used as an alternative in areas where there’s not much fresh water. For example, Singapore is treating waste water and recycling it back into drinking supplies. However people don’t like the idea of drinking water that used to be sewage

Question 61

Haber Process Reaction

Answer 61

. The Haber Process is used to make ammonia from hydrogen and nitrogen using the following reaction:
. N2 + 3H2 = 2NH3 + heat
Nitrogen + Hydrogen = Ammonia + heat

Question 62

Why is the Haber Process Reaction suitable for an industrial scale

Answer 62

The Haber Process is well suited for industrial use as the reactants aren’t too difficult or expensive to obtain

. The Nitrogen is obtained easily from the air, which is 78% nitrogen
. The hydrogen mainly comes from reacting methane (from natural gas) with steam to form hydrogen and carbon dioxide
. The reactant gases are passed over an iron catalyst. A high temperature (450°C) and a high pressure (200 atmospheres) are used
. Because the reaction is reversible, some of the ammonia produced converts back into hydrogen and nitrogen again. It eventually reaches a dynamic equilibrium
. The ammonia is formed as a gas, but as it cools in the condenser it liquifies and is removed. The unused hydrogen (H2) and nitrogen (N2) are recycled, so nothing is wasted.
. The ammonia produced can then be used to make ammonium nitrate - a very nitrogen-rich fertiliser

Question 63

What are the trade offs if the Haber reaction

Answer 63

. The Haber Process is a reversible reaction meaning the there is a trade-off between increasing the rate and maximising the yield

Question 64

Reminder

Answer 64

. Haber proces reaction

Question 65

Fertilisers

Answer 65

. Farmers use manure to fertilise fields. Formulated fertilisers are better as they’re more widely available, easier to use, don’t smell and have just enough of each nutrient so more crops can be grown.

Question 66

What are the essential elements in fertilers

Answer 66

. The three main essential elements in fertilisers are nitrogen, phosphorus and potassium. If plants don’t get enough of these elements, their growth and life processes are affected. These elements may be missing from the soil if they’ve been used up by a previous crop

. Fertilisers replace missing elements or provide more of them. This helps to increase the crop yield, as the crops can grow faster and bigger. For example, fertilisers add more nitrogen to plant proteins, which makes the plants grow faster - increasing producrivity

Question 67

NPK fertilisers

Answer 67

NPK fertilisers are formulations containing salts of nitrogen (N), phosphorus (P) and potassium (K) in the right percentage of elements

Question 68

Ammonia

Answer 68

. Ammonia can be reacted with oxygen and water in a series of reactions to make nitric acid
. You can also react ammonia with acids, including nitric acid, to get ammonium salts
. Ammonium and nitric acid react together to produce ammonium nitrate - this is an especially good compound to use in a fertiliser because it has nitrogen from two sources
. This reaction is carried out differently in industry to how it is done in the lab

Question 69

Ammonium nitrate reaction

Answer 69

NH3 + HNO3 = NH4NO3
Ammonia + Nitric acid = Ammonium nitrate

Question 70

Ammonium nitrate reaction in industry

Answer 70

. The reaction is carried out in giant vats, at high concentration resulting in a very exothermic reaction. The heat released is used to evaporate water from the mixture to make a very concentrated ammonium nitrate product

Question 71

Ammonium nitrate reaction In the lab

Answer 71

. The reaction is carried out on a much smaller scale by titration and crystallisation. The reactants are at a much lower concentration than in industry, so less heat is produced by the reaction and it’s safer for the person to carry it out. After the titration, the mixture needs to be crystallised to give pure ammonium nitrate crystals. Crystallisation isn’t used in industry because it is very slow

Question 72

Potassium chloride and Potassium sulphate

Answer 72

Potassium chloride and Potassium sulphate can be mined and used as a source of potassium

Question 73

Phosphate

Answer 73

Phosphate rock is also mined. However, because the phosphate salts in the rock are insoluble, plants can’t use them as nutrients

Question 74

Reacting phosphate rock with different acids

Answer 74

. Reacting phosphate rock with a number of different types of acids produces soluble phosphates:
. Reaction with nitric acid produces phosphoric acid and calcium nitrate
. Reaction with sulfuric acid produces calcium sulfate and calcium phosphate
. Reaction with phosphoric acid only produces calcium phosphate