C10 - Using Resources

Question 1

What do we use the Earth’s Resources for?
What are these resources produced by?

Answer 1

• Shelter, Warmth, Food & Transport

In many cases, these resources are produced by agriculture provide food, timber, clothing and fuels.

e.g. Cotton from plants. Modern agriculture allows us to grow enough cotton to meet the needs of the world

Humans also plant trees which are used for timber or fuels. Many power stations run on biofuels like woodchips.

Agriculture helps us use the Earth’s resources efficiently

Question 2

What are synthetic alternatives?

Answer 2

In some cases Chemistry has replaced natural resources with a synthetic alternative e.g. rubber as natural rubber comes from the sap of tree whereas synthetic rubber is produced using crude oil.

Question 3

Finite Resources

Answer 3

Some natural resources are finite like fossil fuels. Humans use millions of kilograms of fossil fuels every day. But fossil fuels are produced very slowly so we will end up using them all up.

Metals are also a finite resource. They are extracted from the Earths crust and if we keep using them they will run out.

Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials.

Question 4

Renewable Resources

Answer 4

e.g. wood. We can replace these resources at the same rate which we use them. They will not run out.

Question 5

Why should we make sure human activities are sustainable and what role does Chemistry play in this?

Answer 5

It is really important that human activities are sustainable. We can meet our needs without jeopardizing the future generations.

Chemistry plays a huge role in this. E.g. Artificial fertilisers allow us to grow more food with the land available. It also provides safe drinking water. Furthermore, processes such as Phytomining and bioleaching help us extract metals more easily.

Question 6

What do scientists call potable water and how is it different to pure water?

Answer 6

Drinking water has to have low levels of dissolved salts and cannot have high levels of microbes like bacteria. Scientists call water which is safe to drink **potable water**.

Potable water is not equal to pure water as pure water contains no dissolved substances at all whereas potable water does contain dissolved substances but a low level of them.

Question 7

Where does the UK get their potable water from?
What do countries that do not have fresh water do?

Answer 7

In the uk rain water provides most of our potable water as it has low levels of dissolved substances. It gets collected in the ground in aquifers, lakes, rivers and reservoirs so they are good sources.
In the uk we have access to lots of fresh water which has low levels of dissolved minerals but in many places this is not the case.

Their water might be filled with large amounts of dissolved substances like salts. In this case, Desalination is required to make the water potable. This reduces the levels of dissolved minerals to an acceptable level. Two ways to do this are distillation and reverse osmosis. This is very expensive.

Question 8

How do we produce Potable water?

Answer 8

1. You need a good source of fresh water
2. Then pass the water through filter beds. That is to remove materials such as leaves and suspended particles.
3. Finally, the water is sterilised to kill microbes. In the UK we use chlorine. But in some parts of the world, ozone or UV light is used.

Question 9

Why do we treat waste water?
How do we treat Waste Water?

Answer 9

Waste water contains large amount of organic molecules and contains harmful microorganisms so the waste water must be carefully treated. To do this we:

1. The sewage is screened by passing it through a mesh as this removes solids and pieces of grit.
2. Now the sewage will settle in large sedimentation tanks. This produces a liquid effluent and a semi-solid sludge which sinks.
3. The sludge is taken away and digested by anaerobic bacteria and in the absence of oxygen, they produce biogas which can be burned for electricity
4. At the end, digested sludge can be used for fertilisers in farming
5. The liquid effluent contains large amounts of organic molecules and harmful microorganisms both of these need to be reduced.
6. Therefore, air is bubbled through the liquid effluent. This allows aerobic bacteria to multiply and with the presence of oxygen these bacteria will digest organic molecules and harmful microorganisms.
7. Then the liquid effluent can be safely discharged into nearby rivers or the sea.

Question 10

How is potable water produced in other countries?

What is the easiest way to produce potable water?

Answer 10

In some parts of the world, treated sewage is used directly to produce potable water. However this takes many steps and is only done in areas where water is scarce. Salt water needs to be desalinated.

The easiest way to produce potable water is to use ground water from aquifers. Once treated with chlorine they are safe to drink, but they can sometimes be polluted by fertilisers so water needs to be tested.

Question 11

How are most ores found?
Why are ores becoming Scarce?
What are ores used for?
What are the two ways to extract metals from low-grade ores?

Answer 11

Most metals found in the Earth are already reacted with other elements like oxygen.

But the worldwide demand for metals is growing. They’re ores are extracted from mines. But ores are becoming scarce so we will have to extract copper from low-grade ores(they contain small amounts of the metal).

e.g. copper for electronics and phones.

• Phytomining
  1. This involves growing plants on land containing the metal compound we want.
  2. These plants absorb the metal compound into their tissue.
  3. They are then harvested and burned.
  4. At the end the ash contains a relativley high concentration of the metal compound.
• Bioleaching
  1. Bacteria are mixed with low grade ore
  2. Then the bacteria carry out chemical reactions and produce a soloution called leachate. That contains the metal we want.

Question 12

What do we do at the end of both Phyto mining and Bioleaching?

Why do we need these methods?

Answer 12

Once the copper compounds have been extracted they can be broken down by displacing or electrolysis.

For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron(scrap Iron is cheap) or by electrolysis

These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock.

Question 13

What is an LCA

Answer 13

A LCA are carried out to assess the environmental impact of products.

Question 14

Examples of LCA’s

Answer 14

1. Extracting metals also takes a large amount of energy as ore has to be dug out of the mine and transported for processing.
2. Then the metal has to be extracted from the ore and this can produce large amounts of toxic waste products.
3. Once this is done, we have to manufacture, package and transport our product.
4. All these stages require energy and can produce harmful products
5. First, the oil has to be extracted and then transported to the refineries.
6. Then they have to be separated and cracked
7. Finally the polymer is produced
8. All of these processes take a large amount of energy and alot of the energy will be generated by burning fossil fuels which leads to climate change.

Question 15

What are the four stages of life cycle assessments?

Answer 15

• A life cycle assessment (LCA) is an analysis of the overall environmental impact that a product may have throughout its lifetime
• The cycle is broken down into four main stages which are:
  
  • extracting and processing raw materials
  • manufacturing and packaging
  • use and operation during its lifetime
  • disposal at the end of its useful life, including transport and distribution at each stage.

Diagram showing the four stages in a life-cycle assessment

• Obtaining the necessary raw materials has an impact on the environment which may include:
  
  • Using up limited resources such as ores and crude oil
  • Damaging habitats through deforestation or mining
• Manufacturing processes also have an impact on the environment which may include:
  
  • Using up land for factories
  • The use of fossil fuelled machines for production and transport
• Usage of a product may also affect the environment although it depends on the type of product
• For example, a wooden desk has very little impact whereas a car will have a significant impact (air pollution)
• The disposal of outdated products has an impact on the environment which may include:
  
  • Using up space at landfill sites
  • Whether the product or its parts can be recycled
• A life cycle assessment is carried out using the data of a given product and the criteria of the assessment
• Rarely is there a perfect product with zero environmental impact, so often a compromise is made between environmental impact and economical factors

Question 16

Disadvantages of LCA’s

Answer 16

Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes.

Question 17

Paper shopping bags vs Plastic shopping bags.

Answer 17

• Considering both life-cycle assessments, the plastic bag may be the better option. Even though they aren’t biodegradable, they do have a much longer lifespan and thus are less harmful than paper bags
• Much depends on the usage of the item:
  
  • If the paper bag is recycled then it could be more favourable to use it
  • If the plastic bag is used only once, then then the argument for using plastic bags is less favourable

Question 18

Cons of getting raw materials

How & Why is it important we recycle?

Answer 18

• Quarrying produces large amounts of dust and destroys habitats.
• Mining can release harmful chemicals

It is very important that we recycle as it helps save limited resources and energy while reducing the impact of waste on the environment as there is less waste.

Some products like glass bottles can be reused and can be crushed and melted to make different products.

Whereas some products can be recycled for a different use like plastic bottles which can be recycled to make fleece jackets or carpets.

Metals can be recycled by melting and recasting them. But different metals need separating but it depends on the properties of the final product.

Question 19

What is corrosion?

Why is corrosion a problem?

What is Coating and what are the different types?

Answer 19

Corrosion is the destruction of materials by chemical reactions with substances in the environment.
e.g. Rusting only in Iron and its alloys(steel). In the case of other metals use corroding.
Corrosion is a big problem as it damages materials

But it can be stopped using a barrier and to do that we use grease or paint or coat the material with a metal(Electroplating).

The surface of aluminium naturally reacts with oxygen in the air to form a thin layer of aluminium oxide which protects the metal underneath.

Coating a metal with zinc is called galvanising. These are galvanised nails. This is a barrier but if it gets scratched then it prevents corrosion as zinc is more reactive than iron. This means the zinc corrodes instead of the iron. This is called **Sacrificial protection**.

Question 20

How to carry out experiement for conditions of corrosion?

Answer 20

Question 21

What is an alloy?

Answer 21

An alloy contains a metal blended with other elements. They tend to be harder than pure metals as the layers cannot slide over due to the varying sizes in the atoms.

• Alloys are mixtures of metals where the metals are not chemically combined
• They can also be made from metals mixed with non-metals.
• Alloys often have properties that can be very different from the metals they contain.

Question 22

What are these alloys made of and what are their uses?
BRONZE
BRASS
GOLD
STEEL
ALUMINIUM

Answer 22

• Bronze is an alloy of copper and tin. It is extremely hard and tends not to corrode so it is used in statues
• Brass is an alloy of copper and zinc. Even though it is harder than pure copper it can still be formed into different shapes so it is ideal for musical instruments and door handles
• Gold is used for jewellery. But pure gold is too soft so it is alloyed with silver, copper and zinc to make it harder. The purity is rated in carat 24 = 100%
• Steel is an alloy of iron containing specific amounts of carbon. It also contains other metals.
• High carbon steel is extremely hard but it is also brittle.
• Low carbon steel is softer and more easily shaped so it is used to make car bodies.
• But it can rust so to prevent that stainless steel which also contains chromium and nickel is made.
• Aluminium alloys are low density that makes them really useful in aeroplanes.

Question 23

What are the two types of ceramics you need to know?

Answer 23

• *Glass**
• *Clay Ceramics**

Question 24

How do you make borosilicate glass?
What is borosilicate glass used for?

Answer 24

Borosilicate glass has a higher melting point than soda lime glass. This makes it useful for objects that require heating.

• It is made by mixing
• Sand
• Boron Trioxide

Question 25

How do you make Soda Lime glass? What is Soda lime glass used for?

Answer 25

**Most of the glass we use is called soda lime glass** which is i**deal for windows and bottles.** To make this we mix together: - **sand** - **sodium carbonate** - **limestone**. Then **heat this mix in the furnace until it melts and when it cools** it **can be moulded into any shape we want**. Bu**t there is a problem as it has a low melting point which limits it uses.**

Question 26

Clay ceramics?

Answer 26

**Clay is a mineral found in the ground**. When **it is wet it can be shaped.** It is then **heated in a furnace to harden.** ## Footnote **Used for pottery and bricks**

Question 27

What is a composite and give examples?

Answer 27

Most composites **are made by combining two different materials**. Then we have **reinforcement which consists of fibres or fragments of one material**. The **reinforcement is then surrounded by a matrix or binder material.** The key feature is that **composites have different properties** to the **materials in them** - For example in **Carbon Fibre**: The **reinforcement material is fibres of carbon** and the **matrix is plastic resin**. It is **very strong and light** so it is **useful in cars or in aircraft planes** - Another example is **reinforced concrete**: It has **steel bars surrounded by concrete** which **makes it strong.**

Question 28

What is a polymer. What do their properties depend on? How do you change the properties?

Answer 28

* Depending on the **manufacturing process** used, **the same polymer can have different properties** * **Polythene** for example **can be made at very high pressure and** **moderate temperature** to **produce low density (LD)** **polythen**e **which is** **used for bags and bottles** **where flexibility** is **needed** * If it is **produced at lower temperatures** and **pressures** and **with the use of a catalyst,** * *a much higher density (HD) polythene is produced.** This polymer has a more **rigid, solid** **structure and is used to produce water tanks, mouldings, drain pipes** etc

Question 29

Thermosetting Polymers

Answer 29

**Thermosetting** polymers **do not melt when heated**. They **tend to char and burn when heated**, but t**hey are resistant to much higher temperatures** than **thermosoftening plastics.** They are **used to make electrical plugs, which must not melt, even if there is a malfunction and the wiring inside gets hot.** **Thermosetting** polymers have **strong cross-links between monomers on different polymer** chains t**hat hold the structure together.** These are **strong** **and rigid** **structures** that **don’t soften under heating**

Question 30

Thermosoftening polymers

Answer 30

**Thermosoftening** polymers **melt when heated.** They can **be reshaped when soft.** They **go back to a solid when cooled down.** Most **plastics that we come across** in everyday **life are thermosoftening plastics.** This **means that they can be** **recycled**, which involves **melting them before making a new product.** * **Thermosoftening** polymers consist of **weak intermolecular** **forces** holding the **polymer chains together** * These **polymers therefore** have **low melting points**, can be **melted and remoulded to form different shapes**

Question 31

What is the Haber process used for? What is the equation for the Haber process?

Answer 31

It is used **manufacture ammonia, which can be used to produce nitrogen-based fertilisers.** ## Footnote **The raw materials for the Haber process are nitrogen and hydrogen**

Question 32

What are the sources for Nitrogen, Hydrogen and Ammonia? How is ammonia produced

Answer 32

- You need to know the sources: - **Nitrogen can be extracted from the air** - **Hyrogen** is **produced reacting steam with methane.** - Ammonia is produced by: 1. The **purified Nitrogen and Hydrogen are passed over an iron catalyst at around** **450C** **200 atmospheres pressure.** This causes **some of the nitrogen and hydrogen molecules to react to form ammonia.** 2. This is a **reversible reaction so some of the ammonia breaks down into hydrogen and nitrogen** 3. To i**ncrease the yield we can cool the ammonia and turn it to a liquid which is removed. Then recycle the unreacted nitrogen and Hydrogen back over the catalyst.**

Question 33

Conditions to increase the rate of reaciton in the haber process?

Answer 33

Conditon which increase the rate of reaction: - **450c is a compormise temp.** - The i**ron catalyst increases rate of reaction but has no effect on the postion of the equilibrium.** - **High pressure also pushes the equilibrium to the right hand side.** But **high temps require more energy** **it is extremely expensive and dangerous to work with high pressure.**

Question 34

Le Chatelier's principle

Answer 34

A **cool temperrature makes the reaction slow as the equilibrium will shift to the left.**

Question 35

What are NPK fertilisers? How are NPK fertilisers produced? What do they contain?

Answer 35

They are important fertilisers which contain **Nitrogen, Phosphorus, Potassium** **NPK fertilisers are formulations of various salts** containing **appropriate percentages** of the **elements needed by the plants** are **formulations produced in Industrial Facilities**

Question 36

How do we make ammonium nitrate for NPK fertilisers? How do we get the potassium for NPK fertilisers?

Answer 36

The **main compound of nitrogen in NPK is ammonium nitrate** (**NH4NO3)** it is made by **reacting Ammonia** with **nitric acid.** **Potassium - Potassium chloride, potassium sulfate are obtained by mining, but phosphate rock cannot be used directly as a fertiliser whereas the other two can.**

Question 37

What are the different ways to produce Phosporus for NPK? What is the difference of producing ammonium nitrate in the school vs lab?

Answer 37

**Phosphate rock can be extracted by mining. It has to be chemically processed.** **Nitric acid - By treating Phosphate rock with nitric acid produces phosphoric acid** and **calcium nitrate. But phosphoric acid contains phosphorus but we cannot add this directly to plants so we neutralise it with ammonia to make ammonium phosphate which can be used.** **Sulfuric acid - If we treat phosphoric rock with sulfuric acid we make a mixture of calculim phosphate and calcium sulfate. This is called single superphosphate** **Phosphoric acid - If we treat phosphate rock with phosphoric acid we make triple superphosphate.**

Question 38

What are the stages of the Haber Process?

Answer 38

Ammonia is manufactured using the Haber Process which occurs in five stages The reactants are hydrogen and nitrogen which are extracted from methane and the air respectively Stage 1: **H2 and N2 gases are pumped into the compressor through pipes** Stage 2: The **gases are compressed to about 200 atmospheres inside the compressor** Stage 3: The **pressurised gases are pumped into a tank containing layers of catalytic iron beads at a temperature of 450°C. Some of the hydrogen and nitrogen react to form ammonia in the following reversible reaction:** N2 (g) + 3H2 (g) ⇌ 2NH3 (g) Stage 4: U**nreacted H2 and N2 and product ammonia pass into a cooling tank**. The **ammonia is liquefied and removed to pressurised storage vessels** Stage 5: The **unreacted H2 and N2 gases are recycled back into the system**

Question 39

How do you make ammonia in a labratory?

Answer 39

In the laboratory, ammonium sulfate is made by reacting measured volumes of ammonia solution and sulfuric acid solution. 1. **25 cm³ of ammonia solution is measured** using **a measuring cylinder or volumetric pipette and poured into a conical flask**. 2. T**wo drops of methyl orange** indicator are added. T**his will turn yellow in the alkaline ammonia solution.** 3. **Dilute sulfuric acid is added from a burette slowly** until **the methyl orange indicator** turns **orange. If too much acid is added it will turn red.** 4. The v**olume of sulfuric acid which has been added is recorded**, and t**hen the neutral solution of ammonium sulfate which contains the indicator is thrown away.** 5. The **experiment is repeated without the indicator but with the same volumes of ammonia and sulfuric acid.** 6. The **ammonium sulfate is crystallised by evaporating the water and drying the crystals in an oven or desiccator**.

Question 40

What should you consider when choosing Reaction conditions?

Answer 40

**N2 + 3H2 ⇌ 2NH3** **Temperature: 450ºC** * A **higher** **temperature** would favour the r**everse reaction as it is endothermic** (takes in heat) so a **higher yield of reactants would be made** * If a **lower** **temperature** is **used it favours the forward reaction as it is exothermic** (releases heat) **so a higher yield** of **products** will be made * However **at a lower temperature the rate of reaction** is very **slow** * So **450ºC is a compromise** temperature **between having a** **lower yield** of products but **being made more quickly** **Pressure: 200 atm** * A **lower** **pressure would favour the reverse reaction as the system will try to increase the pressure by creating more molecules** (4 molecules of gaseous reactants) **so a higher yield of reactants will be made** * A **higher** p**ressure would favour the forward reaction** as it will **try to decrease the pressure by creating fewer molecules** (2 molecules of gaseous products) so **a higher yield** **of products** will be **made** * However, **high pressures can be dangerous and very expensive equipment is needed** * So **200 atm is a** **compromise** pressure **between a lower yield of products** being made **safely** and **economically** ***Choosing the conditions for the Haber Process*** **Catalyst** * The **presence of a catalyst does** **not** affect **the position of equilibrium** but **it does increase** the **rate** at **which equilibrium is reached** * This is **because the catalyst increases the rate** of **both** the **forward and backward** **reactions** by th**e same amount** (by providing an alternative pathway requiring **lower activation energy**) * **As a result**, the **concentration** of **reactants and products** is **nevertheless** the **same** **at equilibrium** as **it would be without** the **catalyst**. So a **catalyst is used as it helps the reaction reach equilibrium quicker** * It **allows for an acceptable yield to be achieved at** a **lower temperature** by **lowering the activation energy required** * **Without it the process would have to be carried** out at an even **higher temperature**, increasing **costs** and decreasing **yield** as the higher temperature **decomposes** more of the NH₃ molecules

Question 41

What is the difference between the laboratory and Industrial method of making ammonium sulfate?

Answer 41

In industry **1000s of kgs of ammonia are produced in quickly. This is a continuous process whereas in schools it is produced in small amounts in one go called batch processes.** **In industry concentrated nitric acid and ammonia is used as a gas. This is very dangerous as the reaction is very exothermic and produces heat which is used later on. Whereas in schools dilute acid and small amounts of ammonia are produced which is safe. Instead a bunsen burner or a water bath is used.**

Question 42

Are polymers good conductors of heat and electricity?

Answer 42

* Polymers are **poor conductors of heat and electricity,** hence they are **good thermal** and **electrical** insulators * These **properties** are **extremely useful** for **insulating electrical wiring** as **they prevent** **electric shocks** and **overheating**