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DTT Booster
WJEC Double Science 
THERAPY – Bonding, structure and properties   
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

2. Conduction and convection
WJEC Bonding, structure and properties
Model question
Why do ionic compounds have high melting and boiling points?
Model answer
Ions have strong forces of attraction to ions of an opposite charge. A giant lattice is formed with strong bonds that have to be broken when the compound melts
Ionic
Covalent
Metallic
Formed between metals and non metals
Gain or lose electrons
Strong forces of attraction between ions
High melting point and boiling point
Formed between non metals
Share a pair of electrons
Weak forces of attraction between molecules
Low melting and boiling point
Formed between metals
Force of attraction between free electrons and metal ions.
Free electrons can move and carry charge
High melting and boiling point
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

3. CLICK to reveal MODEL ANSWER
WJEC Bonding, structure and properties
Transfer of electrons from metal to a non metal forming ions.
Held together by strong forces of attraction between oppositely charged ions.
Ionic
bonding
Metals lose electrons.
Non-metals gain electrons.
High melting and boiling points because of the strong forces of attraction.
When dissolved in water, ionic compounds form solutions in which the ions can move. This means the solution can conduct electricity.
Model question
Why can ionic compounds only conduct electricity when molten or dissolved?
CLICK to reveal MODEL ANSWER
Model answer
When molten or dissolved the ions are able to move and so they can conduct electricity. Ions in the solid can’t move so can’t conduct electricity.

4. CLICK to reveal MODEL ANSWER
WJEC Bonding, structure and properties
When you draw ionic bonds it is important that you Clearly show the movement of the electron/s  Show the electrons in their new location Show the overall charges on the ions formed.
Model Question
Draw the ionic bonding for
sodium chloride
CLICK to reveal MODEL ANSWER

5. Conduction and convection
WJEC Bonding, structure and properties
Model Question
Draw a diagram to show the covalent bond between two hydrogen atoms?
Model Answer
Some atoms do not lose electrons but share them in order to fill their outer shell.
CLICK to reveal MODEL ANSWER
This happens between non-metals.
It is called covalent bonding.
Hydrogen can covalently bond to chlorine
A hydrogen A chlorine
atom atom
Covalent bonding
A covalent bond.
Chlorine now has 8 electrons and its outer shell is full
Hydrogen has 2 electrons and its outer shell is full
P1.1.3a/P1.1.1

6. WJEC Bonding, structure and properties
Diamond and graphite are both giant covalent structures and both made of carbon. They are allotropes of each other.
Diamond
Graphite
Each carbon is joined to four other carbon atoms with strong covalent bonds.
Diamond is very hard and has a high melting point.
It does not conduct electricity.
Carbon atoms form layers that can slide over each other.
Each carbon atom joined to only three other carbon atoms with strong covalent bonds.
Graphite conducts electricity as the other electron can move and carry charge.

7. WJEC Bonding, structure and properties
Carbon has several allotropes (substances made of the same elements but with different structures). Examples are diamond, graphite, fullerene and graphene. Their properties make them useful for different purposes.
Graphite is black, shiny and opaque. It is a very slippery material. It's used in pencil leads because it slips easily off the pencil onto the paper and leaves a black mark.
Tube fullerenes are called nanotubes. They are conductors of electricity meaning that nanotubes are used as semiconductors in electronic circuits.
Diamond is extremely hard and has a high melting point. For this reason it's very useful in cutting tools.

8. Ag TiO2 CLICK to reveal MODEL ANSWER
WJEC Bonding, structure and properties
Model question
What useful property does nano silver have?
Model answer
Antibacterial, antifungal and antiseptic properties
Nanochemistry is the study of tiny molecules. It has many potential applications for medical science.
CLICK to reveal MODEL ANSWER
Ag TiO2
Materials have different properties to the bulk materials when they are in the nano scale.
For example, silver nanoparticles have antibacterial properties and can be used in plasters whereas titanium dioxide nanoparticles are so small that they do not reflect visible and so cannot be seen. They are used in sun screens to block harmful ultraviolet light without appearing white on the skin. Normal (large) particles of silver or titanium dioxide do not have these properties.

9. CLICK to reveal MODEL ANSWER
WJEC Bonding, structure and properties
Problems with nanoparticles
So small they cannot be seen
So small that could easily be absorbed through skin
May have unknown properties which could be harmful
Further testing is needed
Model question
Why may people be particularly worried about the use of titanium dioxide in sun cream?
Model answer
Titanium dioxide is used in sunscreens, so is directly applied to the skin. The nanoparticles could be easily absorbed into the body and may cause problems in the future.
CLICK to reveal MODEL ANSWER

10. CLICK to reveal MODEL ANSWER
WJEC Bonding, structure and properties
Smart materials
Thermo chromic
Photo chromic
Shape memory alloy
Shape memory polymer
Hydrogel
Change colour with changing temperature
Forehead thermometer
Change colour with changing light intensity
Transitions lenses in glasses
Returns to original shape with heated
Glasses frames
Stents to hold veins open
Returns to original shape when heated
Self repairing car bodies
Absorb water to swell up to 1000 times their size
Artificial muscles
Nappies
CLICK to reveal MODEL ANSWER
Model answer
Thermochromic material is used as it changes colour with a change in temperature to indicate if the food is too hot.
Model question
Name the smart material that can be used to make baby feeding spoons and state its properties.

11. WJEC Bonding, structure and properties
How are covalent bonds formed?
What kind of bond forms between metals and non metals?
Why do ionic compounds have high melting and boiling points?
What is an allotrope?
Why can’t diamond conduct electricity?
Why is graphite used in lubricants?
What is the special property of photo chromic materials?
Why are hydrogels able to be used in nappies?
Draw the covalent bonding in HCl
Draw the ionic bonding in CaO

12. WJEC Bonding, structure and properties - ANSWERS
How are covalent bonds formed?
A covalent bond is formed from a shared pair of electrons.
2. What kind of bond forms between metals and non metals?
Ionic bonds form where the metal donates electrons and the non metal gains electrons.
3. Why do ionic compounds have high melting and boiling points?
The strong electrostatic attraction between the ions means that they have high melting and boiling points.
4. What is an allotrope?
Allotropes are different forms of the same element. Diamond and graphite are allotropes of carbon.
5. Why can’t diamond conduct electricity?
All of the 4 outer electrons in every carbon are involved in bonds and so are not free to move.

13. WJEC Bonding, structure and properties - ANSWERS
6. Why is graphite used in lubricants?
The weak bonds between layers mean that they can easily slide over each other for use in lubricants.
7. What is the special property of photo chromic materials?
They change colour with a change in light intensity.
8. Why are hydrogels able to be used in nappies?
They can swell to 1000 times their size.
9. Draw the covalent bonding in HCl
10. Draw the ionic bonding in CaO

14. DTT Booster WJEC Chemistry THERAPY WJEC – 2.2 Acids, Bases and Salts
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DTT Booster
WJEC Chemistry
THERAPY WJEC – Acids, Bases and Salts   
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

15. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
The pH Scale
Ions in Solution
Acids contain hydrogen ions (H+(aq)) and alkalis contain hydroxide (OH-(aq)) ions.
We use Universal Indicator to tell the pH of substances.
A colour that matches a pH less than 7 means that the substance is acidic.
If UI turns green, the substance is neutral.
A colour that matches a pH more than 7 means that the substance is alkaline.
Model Question
If Universal Indicator turns orange when it is added to a solution, what can you tell about the solution?
Model Answer
The solution is a weak acid. It contains H+ ions.
CLICK to reveal MODEL ANSWER

16. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
All acids contain hydrogen (HCl, H2SO4, HNO3 etc).
If a metal is more reactive than hydrogen then it will react with an acid by displacing the hydrogen.
When metals react with acids there will be bubbles of hydrogen gas formed.
Model Question
Would lead be expected to react with a dilute acid?
Model Answer
Lead is above hydrogen in the Reactivity Series so lead would displace hydrogen. In reality, lead is only just more reactive than hydrogen and so the reaction is very, very slow.
CLICK to reveal MODEL ANSWER
Metal Salt
Acid Hydrogen

17. Conduction and convection
WJEC 2.2 Acids, Bases and Salts
Model Question
What products would form if sulphuric acid reacted with magnesium carbonate?
Model Answer
Magnesium sulfate (a salt)
Water
Carbon dioxide
Neutralisation Reactions
CLICK to reveal MODEL ANSWER
What is a base?
A base is a substance that will react with an acid to make it neutral.
If the base can dissolve in water (not all of them do) then the substance is also an alkali.
Metal carbonates are bases. As well as producing a salt and water when they react with acids (like other bases), they also produce carbon dioxide.
Acid Salt
Base Water
Hydrochloric acid copper(II) chloride
Copper carbonate water +
carbon dioxide
Metal oxides and metal hydroxides are bases.
HCl + NaOH NaCl + H2O
HCl + CuCO3 CuCl2 + H2O + CO2
2HNO3 + CuO Cu(NO3)2 + H2O
P1.1.3a/P1.1.1

18. Conduction and convection
WJEC 2.4 Chemical Reactions and Energy
Testing For Acids
Model Question
A colourless solution is mixed with a white powder and there is a reaction with fizzing. A pupil says that the powder was a carbonate. What test can be done to make sure?
Model Answer
The experiment is repeated and the gas is bubbled through limewater. If the limewater turns milky the gas is carbon dioxide and the powder must have been a carbonate.
Metal carbonates are bases. As well as producing a salt and water when they react with acids (like other bases), they also produce carbon dioxide.
To test for an acid:
Add a carbonate and look for fizzing.
CLICK to reveal MODEL ANSWER
Testing For Carbonates
Metal carbonates are bases. As well as producing a salt and water when they react with acids (like other bases), they also produce carbon dioxide.
To test for a carbonate:
Add an acid and look for fizzing.
Testing for CO2
P1.1.3a/P1.1.1

19. Conduction and convection
WJEC 2.2 Acids, Bases and Salts
Making Salts from Insoluble Bases
Insoluble bases do not dissolve (INsoluble). The base is added to the acid until no more will react (it is in excess). You know when this has happened as the mixture is not clear (you can see bits in it). You then filter to remove the excess base and then evaporate to remove water and leave crystals of the salt.
Model Question
Which acid and which insoluble base have been reacted together in the diagram above?
Model Answer
Sulfuric acid
Copper oxide / Copper carbonate
(React to form copper(II) sulfate)
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

20. Conduction and convection
WJEC 2.2 Acids, Bases and Salts
Naming Salts
Metal / Base
Acid
Hydrochloric
Sulfuric
Nitric
Magnesium
Magnesium chloride
Magnesium sulfate
Magnesium nitrate
Copper carbonate
Copper chloride
Copper sulfate
Copper nitrate
Zinc oxide
Zinc chloride
Zinc sulfate
Zinc nitrate
Calcium carbonate
Calcium chloride
Calcium sulfate
Calcium nitrate
Iron(III) oxide
Iron(III) chloride
Iron sulfate
Iron nitrate
The first part of the name of a salt comes from the metal or the base that is reacting.
The second part of the name comes from the acid.
Hydrochloric acid makes chlorides
Sulfuric acid makes sulfates
Nitric acid makes nitrates
Model Question
What chemicals could be reacted together to make sodium sulfate?
Model Answer
Sodium metal (not recommended) / sodium oxide / sodium hydroxide / sodium carbonate and sulphuric acid.
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

21. Testing for Sulfates (SO42-) CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
Testing for Sulfates (SO42-)
Barium sulfate is extremely insoluble (it will not dissolve).
When barium sulfate is formed from two solutions, a thick white precipitate is formed.
Model Question
You have a white powder. How would you test the powder to see if it is a sulfate?
Model Answer
You have to dissolve some of the powder first to get a clear solution. Then you add barium chloride solution. If the powder is a sulfate then a thick white precipitate will form.
CLICK to reveal MODEL ANSWER
Precipitate:
A solid formed from two solutions.
What you do
What you see
Add barium chloride solution
A thick white precipitate forms

22. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
Titration Part1
Usually:
25cm3 of acid is measured accurately using a pipette.
The acid goes into a flask with a few drops of indicator.
The base is added from the burette until one drop of base changes the colour of the indicator.
Titration is the name given to a method that allows you to react very accurate volumes of solutions.
Once you know the volume to add, the experiment can be repeated without an indicator. Pure crystals of the salt formed can then be obtained by evaporation.
Model Question
Why is a white tile placed underneath the flask?
Model Answer
A white tile is used so that it is easier to see when there has been a colour change.
CLICK to reveal MODEL ANSWER

23. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
Titration Part 2
Accuracy
How close your answer is to the correct value.
Precision
How close your results are to each other.
Titrations should be both accurate and precise.
Titre:
The name given to the total volume that is added.
Volume (cm3)
Rough 1 2 3
Final
26.0
25.4
27.4
Initial
0.0
0.2
2.3
Titre (total added)
25.2
25.8
25.1
Model Question
What is the value for the total volume added that should be used in a calculation based on the example results opposite?
Model Answer
( ) ÷ 2 = cm3
In this example, 1 and 3 would be used to give the average value. We can’t use the rough value and 2 is too far from 1 and 3 to be accurate.
CLICK to reveal MODEL ANSWER

24. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
Titration Part 3 - HT
At the end point (when the colour changes - neutralisation):
for most titrations, the number of moles of acid is the same as the number of moles of alkali.
Titrations allow you to calculate the concentrations of solutions. If you know the accurate volume of either the acid or the alkali then you can work out the other.
Model Question
If the acid on the left was neutralised by 20 cm3 of sodium hydroxide, NaOH, what was the concentration of NaOH?
Model Answer
HCl + NaOH = NaCl + H2O
At neutralisation, moles HCl = moles NaOH
Moles HCl = (see left)
So, moles NaOH =
Concentration = moles ÷ volume
= ÷ 0.02
= mol/dm3
Concentration x volume = moles
Example
How many moles of hydrochloric acid are there in 25 cm3 of 0.1 mol/dm3 HCl?
Moles = x 0.1 = moles
Volumes are always converted to litres. To do this, take the value in cm3 and ÷ 1000.
CLICK to reveal MODEL ANSWER

25. CLICK to reveal MODEL ANSWER
WJEC 2.2 Acids, Bases and Salts
Strong and Weak Acids
Acids split up (dissociate) in solution to give H+(aq) ions.
100% of the particles in a strong acid split up to give H+(aq) ions.
HCl(aq) H+(aq) + OH-(aq)
Only a small number of the particles in a weak acid will dissociate. Most stay as the full molecule.
CH3COOH(aq) CH3COO-(aq) + H+(aq)
Strong is not the same as concentrated.
Weak is not the same as dilute.
Model Question
How can you have a dilute solution of a strong acid?
Model Answer
Some acids like HCl or H2SO4 are strong acids as all of the particles dissociate to give H+(aq) ions. If you mix in lots of water the acid is dilute.
CLICK to reveal MODEL ANSWER
Dilute acids do not have many acid particles dissolved in them. If you dissolve more acid particles the acid becomes more concentrated.

26. WJEC 2.2 Acids, Bases and Salts
What pH number would a weak alkali have?
What ions are found in (a) acids and (b) alkalis?
How can you use the Reactivity Series to tell if a metal will react with an acid?
Finish these equations:
Acid + Metal
Acid + Base
Acid + Carbonate
How do you test for a carbonate?
Complete the sentences for the method to prepare a salt from an insoluble base:
Add the base to the acid until the base is ……………………….
………………….. The mixture to leave the solution of the salt.
………………………………………. and then leave overnight for crystals to form.

27. WJEC 2.2 Acids, Bases and Salts
Name the salt formed from magnesium carbonate and sulphuric acid.
Explain how you test for sulfates.
Why are titrations so useful?
What is a strong acid?

28. WJEC 2.2 Acids, Bases and Salts
What pH number would a weak alkali have?
Between 8 and 10. More than 7 is alkaline.
What ions are found in (a) acids and (b) alkalis?
(a) H+(aq) (b) OH-(aq)
How can you use the Reactivity Series to tell if a metal will react with an acid?
If a metal is above hydrogen in the Reactivity Series then the metal will react with dilute acid by displacing hydrogen.
Finish these equations:
Acid + Metal salt + hydrogen
Acid + Base salt + water
Acid + Carbonate salt + water + carbon dioxide

29. WJEC 2.2 Acids, Bases and Salts
How do you test for a carbonate?
Add an acid. If there is fizzing, test the gas by bubbling through limewater. If the limewater turns milky the gas was carbon dioxide and the substance was a carbonate.
Complete the sentences for the method to prepare a salt from an insoluble base:
Add the base to the acid until the base is in excess.
Filter the mixture to leave the solution of the salt.
Evaporate by a third and then leave overnight for crystals to form.

30. WJEC 2.2 Acids, Bases and Salts
Name the salt formed from magnesium carbonate and sulphuric acid.
magnesium sulfate
Explain how you test for sulfates.
Add barium chloride. A sulfate gives a thick white precipitate.
Why are titrations so useful?
They tell you very accurately when an acid and an alkali have neutralised each other.
What is a strong acid?
An acid where 100% of the particles dissociate to give H+(aq) ions.

31. DTT Booster WJEC Chemistry
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DTT Booster
WJEC Chemistry 
THERAPY Topic – Metals and their extraction – Part one   
Commissioned by The PiXL Club Ltd.
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

32. Conduction and convection
WJEC Metals and their extraction – part one
Rocks contain metal compounds. If the metal compound can be economically extracted we call the rock an ore. The metal is often combined with oxygen.
Ores are mined and then purified.
The Reactivity Series
Model Question: Why can metal ores rich in metals above carbon not be extracted by heating with carbon?
Model Answer:
They are more reactive than carbon so carbon will not be able to reduce the elements (oxygen) in the metal ore
Potassium
Sodium
Calcium
Magnesium
Aluminium
Zinc
Iron
Lead
Copper
Silver
Gold
Increasing reactivity
Please
Send
Charlie's
Monkeys
And
CARBON
Zebras In
Cages
Securely
Guarded
CRAZY!
CLICK to reveal MODEL ANSWER
The reactivity of a metal determines the method of extraction. Metals above carbon must be extracted using electrolysis. Metals below carbon can be extracted by reduction using carbon, coke, or charcoal. Gold and silver do not need to be extracted. They occur native (naturally).
During electrolysis: In a solution or molten compound when electricity is passed through it positive metal ions move towards the negative electrode. Negative non metal ions move towards the positive electrode.
P1.1.3a/P1.1.1

33. WJEC Metals and their extraction – part one
The reactivity of a metal can be used to predict the outcome of a chemical reaction. In a displacement reaction the more reactive metal will displace (push out) the less reactive metal. Displacement reactions involve a metal and a compound of a different metal.
Displacement reactions are easily seen when a salt of the less reactive metal is in the solution. During the reaction:
the more reactive metal gradually disappears as it forms a solution
the less reactive metal coats the surface of the more reactive metal
Model Question:
What would you predict would happen when you zinc was added to silver chloride.
Model Answer:
The zinc would displace the silver in the chloride solution. Silver would be deposited on the zinc.

34. aluminium + iron(III) oxide → iron + aluminium oxide
WJEC Metals and their extraction – part one
An example of a displacement reaction is the thermite reaction. It is often used on railway lines to produce white hot molten (liquid) iron.
Heat is needed to start the reaction, but then it releases an incredible amount of heat it is an example of an exothermic reaction. The heat is enough to melt the iron. The reaction is:
aluminium + iron(III) oxide → iron + aluminium oxide
2Al + Fe2O3 → 2Fe + Al2O3
Because aluminium is more reactive than iron, it displaces iron from iron(III) oxide. The aluminium removes oxygen from the iron(III) oxide. Oxidation is gaining of oxygen – aluminium is oxidised. Reduction is losing oxygen – iron oxide is reduced.
Model Question:
Why would the thermite reaction be used on railway lines to replace iron?
Model Answer:
It is extremely difficult to transport the liquid iron to remote areas of the railway line.

35. WJEC Metals and their extraction – part one
Raw Materials
Iron ore (Iron oxide) – provides the iron.
Coke – provides the carbon needed to make the carbon monoxide.
Limestone – reacts with the impurities to make slag.
Air – provides the oxygen needed to react with the carbon
Iron is produced in the blast furnace. It is an oxidation and reduction reaction.
Iron ores such as haematite contain iron oxide. The iron ore is added at the top of the furnace with coke and limestone. The coke reacts with the oxygen in the air to form first carbon dioxide and then carbon monoxide. In the blast furnace, it is so hot that carbon monoxide can be used to reduce the iron oxide in place of carbon:
iron oxide + carbon monoxide    →    iron + carbon dioxide
Fe2O3 + 3CO    →    2Fe + 3CO2
The oxygen must be removed from the iron oxide to leave the iron behind. The iron oxide is reduced and the carbon monoxide is oxidised.
Carbon is more reactive than iron, so it can push out or displace the iron from iron oxide.
iron oxide + carbon    →    iron + carbon dioxide
2Fe2O3 + 3C    →    4Fe + 3CO2

36. WJEC Metals and their extraction – part one
Iron – is mostly used to make steel. It is used in many airs such as construction, railways, cutlery etc. Due to its strength and resistance to corrosion.
Aluminium - used in cans, foil, window frame and aircraft. Due to its low density.
Titanium – used in hip replacements and used to make alloys with aluminium. Due to its low density and resistance to corrosion.
Metals and their uses
Metals are used in many different areas due to their metallic properties. The physical properties of solid metals are:
conduct heat.
conduct electricity.
generally high melting and boiling points.
strong.
malleable (can be hammered or pressed out of shape without breaking)
ductile (able to be drawn into a wire)
metallic lustre.
opaque (reflect light)
Model Question:
Why would aluminium be used to make saucepans?
Model Answer:
Conducts heat and is low in density.

37. CLICK to reveal MODEL ANSWER
WJEC Metals and their extraction – part one
Model Question:
Explain why metal alloys are more useful than pure metals.
Model Answer:
The other element disrupts the regular pattern of the pure metal.
This makes the metal harder and stronger.
Other alloys can give metals other useful properties.
A metal mixed with other elements is called an ALLOY. Alloys are harder than pure metals.
CLICK to reveal MODEL ANSWER
Pure metal – regular pattern layers slide easily over each other.
Alloy – other element disrupts regular pattern layers DO NOT slide easily over each other.
IRON ALLOYS
Steel  Iron with carbon and/or other elements. Impurities make it brittle. There are a number of types of steel alloys: Low carbon steel – easily shaped, High carbon steels – very hard, Stainless steels – resistant to corrosion
ALUMINIUM ALLOYS
Aluminium naturally soft
Mixed with wide range of other elements
All have very different properties
E.g. in aircraft or armour plating!
COPPER ALLOYS
Copper naturally soft
Bronze (Copper + Tin) Tough, Resistant to corrosion, Brass (Copper + Zinc),
Harder but workable
GOLD ALLOYS
Gold naturally soft
Usually add Copper to make jewellery stronger and last longer.

38. Metals and their extraction - Questions
1. Where do most metals originate? 2. Describe two ways of extracting metals from their ores. 3. Name the top two and bottom two metals in the reactivity series. 4. What type of reaction involves gain of oxygen? 5. What is the thermite reaction? 6. What are the four raw materials in the blast furnace? 7. Why can carbon be used to extract iron from iron oxide? 8. Why is copper used for electrical wires? 9. What is an alloy? 10. Why is iron often alloyed?

39. Metal ores and metal alloys - Answers
1. Where do most metals originate? In the Earth’s crust as ores 2. Describe two ways of extracting metals from their ores. Heating with carbon or electrolysis 3. Name the top two and bottom two metals in the reactivity series. Potassium, sodium and gold, platinum 4. What type of reaction involves gain of oxygen? Oxidation 5. What is the thermite reaction? Aluminum + Iron oxide → Iron + Aluminum oxide 6. What are the four raw materials in the blast furnace? Iron ore, coke, limestone and air. 7. Why can carbon be used to extract iron from iron oxide? Carbon is more reactive than iron. 8. Why is copper used for electrical wires? It is a good electrical conductor 9. What is an alloy? A metal mixed with another element 10. Why is iron often alloyed? To increase its strength and reduce corrosion.

40. WJEC Double Award Science – Chemistry
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DTT Booster
WJEC Double Award Science – Chemistry  
THERAPY Topic – Metal and their extraction
Part two   
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

41. Conduction and convection
WJEC Metals Part Two
One way of freeing up the ions is by melting the substance.
Electrolysis
Electro lysis
Electricity to break down
Electrolysis is a way of obtaining metals from their ores.
We use electrolysis to obtain metals that cannot be extracted using carbon as they are too reactive.
Model Question
If you melt sodium chloride, which two ions are released?
What are the charges on them?
Model Answer
Sodium ions (Na+) and chloride ions (Cl-)
For electrolysis to happen we must have freely moving ions.
The substance must be ionic and the ions must be free to move.
CLICK to reveal MODEL ANSWER
As a solid the ions are all fixed in position.
P1.1.3a/P1.1.1

42. Conduction and convection
WJEC Metals Part Two
Model Question
In electrolysis we have two electrodes, a positive and a negative, which ions are attracted to which?
Model Answer
Positive to negative and negative to positive
We can also release ions by dissolving them in water.
CLICK to reveal MODEL ANSWER
Once dissolved and molten the ions move around freely and randomly.
We can put electrodes into the molten substance or the mixture.
An electrode is simply an electrical conductor that can withstand the conditions and / or not react with the substances.
Carbon rods are often used.
The water molecules surround the ions and carry them into solution.
P1.1.3a/P1.1.1

43. Conduction and convection
WJEC Metals Part Two
Model Question
How many electrons are needed to convert:
Al3+ to Al and K+ to K
Model Answer
Al3+ needs 3 K+ needs 1
Electrolysis of molten substances
If we melt lead bromide, the lead ions and the bromide ions are now free to move. There are the positive lead ions, Pb2+ and negative bromide ions, Br -.
CLICK to reveal MODEL ANSWER
When a lead ion, Pb2+ touches the negatively charged electrode it collects , in this case, 2 negative electrons.
We can write this as:
Pb2+ +2e-  Pb
e- stands for an electron
As you can see our lead ion has now become a lead atom.
We have extracted lead from lead bromide.
When an electric current is passed the ions will move to the oppositely charged electrode.
At the same time this is happening two electrons must be taken from somewhere; this is happening at the other electrode.
P1.1.3a/P1.1.1

44. Conduction and convection
WJEC Metals Part Two
Model Question
Mercury is an unreactive metal. What would happen at each electrode if we carried out electrolysis of mercury chloride, HgCl2? Mercury is Hg2+
Model Answer
At the negative: Hg2+ + 2e -  Hg
At the positive: 2Cl -  Cl2 + 2e -
At the positive electrode, an electron is taken from the bromide ion, Br -, as we are missing two electrons another electron is taken from a second bromide.
2Br -  Br2 + 2e -
Two bromide ions lose their electrons and become a molecule of bromine.
Notice how we write electrons on the right.
CLICK to reveal MODEL ANSWER
Electrolysis of solutions
If we can dissolve a substance in water its ions are also free to move so we can carry out electrolysis on a solution.
Electrolysis of copper chloride solution.
Copper chloride, CuCl2 will dissolve in water to give Cu2+ and 2 Cl -
At the negative electrode:
Cu2+ + 2e -  Cu
At the positive electrode:
2Cl -  Cl2 + 2e -
The idea is the same, opposites attract, the negative electrode gives up electrons and the positive electrode takes electrons.
We will only get a metal produced if it is unreactive as it is competing with positive hydrogen ions, H+, from the water.
P1.1.3a/P1.1.1

45. Conduction and convection
WJEC Metals Part Two
Model Question
How does adding cryolite to the mixture make aluminium production more profitable?
Model Answer
Lower temperature needed to melt it so lower energy costs
Electrolysis is important for extracting metals.
Aluminium is far too reactive to be extracted from its oxide with carbon; we have to use electrolysis.
CLICK to reveal MODEL ANSWER
The problem is that aluminium oxide melts at a very high temperature (over 2000oC), so a substance called cryolite is added to it that lowers its melting point to around 900oC.
Aluminium oxide has the formula Al2O3
When molten its ions are released:
Al3+ and O2-
The aluminium ions are attracted to the negative electrode: Al3+ + 3e -  Al
At the positive electrode the oxide ions turn to oxygen: 2O2-  O2 + 4e -
Molten aluminium oxide
The oxygen formed reacts with the graphite electrodes to make carbon dioxide.
P1.1.3a/P1.1.1

46. CLICK to reveal MODEL ANSWER
WJEC Metals Part Two
Results of test
The sodium hydroxide is added to a solution containing the transition metal ion. A precipitate (ppt) is formed. Below is the ion with the colour of the ppt formed.
Fe 2+ = green ppt turns brown upon standing
Fe 3+ = orange brown ppt
Cu 2+ = blue ppt
Transition metals
The transition metal are elements in the centre of the periodic table, between groups 2 and 3. Most of the commonly used metals are there, including iron, copper, silver and gold. The transition metal ions can be identified by using a precipitation test with sodium hydroxide.
Model Question:
If you added Iron(II) chloride to sodium hydroxide what would you observe?
Model Answer:
A green ppt which would turn brown upon standing.
CLICK to reveal MODEL ANSWER

47. Placement of an electrolysis industry unit
WJEC Metals Part Two
Placement of an electrolysis industry unit
The following points must be taken into consideration:
siting of plants – are there transport links into and out of the plant and is there a local work forces.
Raw materials – how close or easy to transport the raw materials for the process.
fuel and energy costs – cheap reliable energy source close to the industry is essential.
greenhouse emissions – how far away are local housing and the effect of the process on the environment.
Recycling – is there capability of recycling material locally and reduce costs.
A lot needs to be considered before the final placement of an industrial unit involving electrolysis. The factors affecting economic viability and sustainability of extraction processes must be reviewed.
Model Question:
Why are many industrial sites by the coast?
Model Answer:
Transport of the raw material or product by sea, cheaper than road or rail.
CLICK to reveal MODEL ANSWER

48. WJEC Metals Part Two What does electrolysis mean?
In what state does a compound need to be in order to carry out electrolysis?
What do we call an atom that has lost or gained an electron?
Name the force that exists between an atom that has lost an electron and an atom that has gained one.
How would you test for the following transition ions and what would be the expected results: Iron (II), Iron (III) and Copper?
What are the products of the electrolysis of water and how could you identify them?
Give five factors which must be considered when placing an industrial unit?

49. WJEC Metals Part Two - Answers
What does electrolysis mean? Splitting a compound using electricity.
In what state does a compound need to be in order to carry out electrolysis? Molten or dissolved in water.
What do we call an atom that has lost or gained an electron? An ion
Name the force that exists between an atom that has lost an electron and an atom that has gained one. Ionic
How would you test for the following transition ions and what would be the expected results: Iron (II), Iron (III) and Copper?
Test using sodium hydroxide. Expected results : Iron (II) – green ppt, Iron (III) – orange brown ppt and copper – blue ppt.
6. What are the products of the electrolysis of water and how could you identify them?
The products are hydrogen and oxygen. You can test the hydrogen with a lighted splint and it goes pop, and the oxygen test with a glowing splint and will re-light.
7. Give five factors which must be considered when placing an industrial unit?
Need to consider: siting of plant, fuel and energy sources, raw materials, greenhouse emissions and recycling.

50. DTT Booster WJEC Chemistry
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DTT Booster
WJEC Chemistry
THERAPY WJEC – 5.4 Chemical Reactions and Energy   
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

51. What Happens in Reactions?
WJEC 5.4 Chemical Reactions and Energy
What Happens in Reactions?
During a chemical reaction bonds are broken and new bonds form.
The bonds in the reactants are broken.
New bonds in the products are formed.
Breaking bonds requires energy to be put in.
When new bonds are formed, energy is released.

52. CLICK to reveal MODEL ANSWER
WJEC 5.4 Chemical Reactions and Energy
Model Question
How would a test tube feel to the touch if there were an exothermic reaction going on inside it?
Model Answer
The tube would feel warm. Energy is released to the surroundings. When you touch the tube the surroundings = you.
Exothermic Reactions
More energy is given out than it takes to break the bonds in the reactants.
CLICK to reveal MODEL ANSWER
This graph shows the energy contained in the molecules of the reaction not the energy of the solution or the surroundings.
Overall, energy is given out by our reaction. This energy is given out to the surroundings.
After an exothermic reaction is over the molecules formed contain less energy in their bonds than at the start of the reaction.
The energy lost goes to the surroundings.
As you can see, after the reaction the products contain less energy than the reactants – an increase shows that energy is lost by the chemicals to the surroundings.

53. Conduction and convection
WJEC 5.4 Chemical Reactions and Energy
Model Question
How would a test tube feel to the touch if there were an endothermic reaction going on inside it?
Model Answer
The tube would feel cold. Extra energy is taken in from the surroundings. When you touch the tube the surroundings = you.
Endothermic Reactions
More energy is taken in from the surroundings than is given out when new bonds form.
CLICK to reveal MODEL ANSWER
This graph shows the energy contained in the molecules of the reaction not the energy of the solution or the surroundings.
Energy is taken in by our reaction. This energy is taken from the surroundings – We can feel this energy loss as a cooling of the surroundings.
After an endothermic reaction is over the molecules formed contain more energy in their bonds than at the start of the reaction.
The extra energy comes from the surroundings.
As you can see, after the reaction the products contain more energy than the reactants – an increase shows that energy is gained by the chemicals from the surroundings.
P1.1.3a/P1.1.1

54. Conduction and convection
WJEC 5.4 Chemical Reactions and Energy
Model Question
Two reactions were carried out in a test tube, in which reaction would you feel the test tube warming up?
Model Answer
Tube A
Exothermic
CLICK to reveal MODEL ANSWER
Endothermic
The size of the energy gap is important!
The bigger the gap the bigger the energy change.
In the two diagrams opposite you can see that the energy change for the endothermic reaction is greater than that for the exothermic.
P1.1.3a/P1.1.1

55. Conduction and convection
WJEC 5.4 Chemical Reactions and Energy
If I wanted to warm up 1g of water by 1oC it would take me exactly 4.2J of energy. This figure is called the specific heat capacity of water.
Measuring energy change
We can measure the change in energy of a reaction by measuring the temperature of the reaction mixture or by the change in temperature of water.
If we measure the temperature change we could say which reaction is exothermic or endothermic, we could also compare which is most exothermic or endothermic depending on the size of the temperature change.
There is an equation that links temperature change of water and how much energy is absorbed or taken.
Energy = mass x temperature x heat capacity
of water change of water
Example: 50g of water is warmed up by 5°C. What is the energy change?
Energy = mass x temperature x heat capacity
of water change of water
Energy = x x
Energy = 1,050J
Model Question
How much energy would it take to warm up 100g of water by 10oC?
Model Answer
Energy = 100 x 10 x 4.2
Energy = 4200J
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

56. Conduction and convection
WJEC 5.4 Chemical Reactions and Energy
Model Question
Why might allowing an experiment like the one below continue until the water boils lead to inaccuracy in your results?
Model Answer
If the water boils then you are losing hot steam - energy is being lost to the air
We can use this equation in experiments to calculate the energy change when a reaction happens.
For example burning a fuel.
The energy released by the burning fuel is captured by the water in the can, warming it up
CLICK to reveal MODEL ANSWER
You will always be given the heat capacity of water – 4.2 J / g oC
Somewhere in the question they will tell you how much water is used and the temperature change.
You should also remember that not all of the energy will be absorbed by the water, some will warm up the can, or the thermometer, some will be lost to the surroundings
If the temperature of the water rose by 20oC and the heat capacity of water is 4.2.
E = mass x heat capacity x temp rise
E = 100 x 4.2 x 20
E = 8400J
P1.1.3a/P1.1.1

57. CLICK to reveal MODEL ANSWER
WJEC 5.4 Chemical Reactions and Energy
Model Question
Reaction B is an endothermic reaction. Draw a line to show that there is an activation energy needed for a collision to be successful and a reaction to take place.
Model Answer
Activation Energy
Reactions between particles can only happen when particles collide.
There is a minimum energy that an individual collision needs to result in a reaction taking place.
The minimum energy is known as the activation energy.
CLICK to reveal MODEL ANSWER
The activation energy can be thought of as an energy barrier. If the energy is low energy then the particles will not get over the barrier; they will just bounce apart and no reaction will take place.

58. CLICK to reveal MODEL ANSWER
WJEC 5.4 Chemical Reactions and Energy
Bond Energies
Energy has to go in to break bonds in the reactants.
Energy is released when new bonds are made in the products.
Example
2H O=O = H2O
H-H H-H + O=O = H-O-H + H-O-H
Calculate the energy required to break the bonds in the reactants.
(2 x H-H) + (1 x O=O) = (2 x 436) + (1 x 498)
= 1370kJ
Calculate the energy released when the products are formed.
(4 x 467) = kJ
Calculate the overall energy change.
Overall energy = Energy In – Energy Out
= 1370 – 1868
= - 498kJ
The negative overall value means that the reaction is exothermic.
You may have to calculate the amount of energy that is given out or taken in during a reaction. To do this you use bond energies. You will be given any bond energies that you need.
Model Question
If a reaction is endothermic, what can you say about the overall energy change? Model Answer
It will be a positive value as the particles gain energy from the surroundings.
CLICK to reveal MODEL ANSWER

59. WJEC 5.4 Chemical Reactions and Energy
In an exothermic reaction is energy lost or gained by the chemicals?
Which graph, A or B, shows an endothermic change?
A liquid fuel was burnt, the heat released was captured by a copper can containing 250g of water. The water rose by 16oC The specific heat capacity of water is 4.2 J/ g oC Calculate the energy transferred to the water. If this required 0.84g of fuel to be burnt, how much energy does 1g of fuel release?

60. WJEC 5.4 Chemical Reactions and Energy
For the following reaction:
Bond energies: C-H = 416; C=C = 598; H-O = 467; C-C = 356; C-O = 336
Calculate the energy required to break the bonds in the reactants.
Calculate the energy released when the bonds in the products are formed.
Calculate the overall energy change for the reaction and say if it is exothermic or endothermic.

61. WJEC 5.4 Chemical Reactions and Energy
In an exothermic reaction is energy lost or gained by the chemicals? Lost
Which graph, A or B, shows an endothermic change? B
A liquid fuel was burnt, the heat released was captured by a copper can containing 250g of water. The water rose by 16oC The specific heat capacity of water is 4.2 J/ g oC Calculate the energy transferred to the water. E = 250 x 16 x 4.2 = 16,800J If this required 0.84g of fuel to be burnt, how much energy does 1g of fuel release?
16800/0.84 = 20,000J

62. WJEC 5.4 Chemical Reactions and Energy
For the following reaction:
Bond energies: C-H = 416; C=C = 598; H-O = 467; C-C = 356; C-O = 336
Calculate the energy required to break the bonds in the reactants.
(1 x 598) + (4 x 416) + (2 x 467) = 3196kJ
b) Calculate the energy released when the bonds in the products are formed.
(1 x 356) + (5 x 416) + (1 x 336) + (1 x 467) = 3239kJ
c) Calculate the overall energy change for the reaction and say if it is exothermic or endothermic.
Overall = Energy In – Energy Out = 3196 – 3239 = -43kJ
The overall energy is negative so the reaction is exothermic.

63. DTT Booster WJEC Chemistry THERAPY Topic - Crude oil part 1
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DTT Booster
WJEC Chemistry
THERAPY Topic - Crude oil part 1  
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

64. CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Crude oil
Crude oil is formed from the remains of tiny marine plants and animals. When they died their remains sank to the seabed and they were buried in layers of silt and sand. The pressure and heat, together with the absence of oxygen, on the decaying plants and animals changed them into crude oil and natural gas.
Fossil fuels
There are three forms of fossil fuel – Coal, Oil and Natural Gas. All three fossil fuels were formed hundreds of millions of year ago. The process of their formation is a type of fossilisation. For this reason they are called Fossil Fuels. They are finite resources as already supplies are running out. It is estimated that supplies of fossils fuels will be exhausted in less than a hundred years.
Model Question:
Can you explain how crude oil is formed?
Model Answer
Remains of dead tiny marine plants and animals break down over millions of years in the absence of oxygen.
CLICK to reveal MODEL ANSWER

65. Conduction and convection
WJEC Crude oil part one   
Nearly all the compounds in crude oil are hydrocarbons (hydrogen and carbon only). Most of these are ALKANES. Alkanes have all single bonds and the general formula CnH2n+2.
Methane CH4
Ethane C2H6
Propane C3H8
Crude oil is evaporated and the vapour is passed into the column. The vapour condenses at different temperatures within the fractioning column. Each fraction has a different boiling point range as fractions contain mixtures of compounds with similar number of carbons.
Fractional distillation
 Refinery Gas (fuel)
 Petrol (cars)
 Naphtha (industry)
 Kerosene (jet fuel)
 Diesel (engines)
 Residue (road surface)
Model Question:
In a fractionating column where do fractions with shorter carbon chains condense? Explain your answer.
Model Answer
Fractions with shorter carbon chains condense at the top.
The shorter the chains, the less energy is needed to break the forces between the chains.
So they have a lower boiling point.
Distillation
Fractional
Fractions with low boiling points condense at the top.
CLICK to reveal MODEL ANSWER
Longer chains mean…
Greater viscosity (less ability to flow)
Less flammable
Less volatile
Higher boiling point
P1.1.3a/P1.1.1

66. Social, environmental and economic impact CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Social, environmental and economic impact
It is easy to say just use less oil and then the reserves will last longer. However there are a number of things that need to be considered when we talk about using less oil. These are the Social impact, the Economic impact and the Environmental impact. The decisions made about the use of crude oil impact on all aspects of people’s lives all over the World.
Social : this is the impact the oil industry has upon the local area and a person’s social life. For example, the impact of using kerosene as fuel in planes.
Model Question:
State the positive effects on the environment if crude oil usage was reduced?
Model Answer
The following environmental issues would reduce: oil spillages in oceans, reduction in gases which affect global warming and acid rain.
Environmental : this is the impact that the oil industry has on the environment. For example, oil spills and how they affect the environment.
CLICK to reveal MODEL ANSWER
Economic : this is the impact the oil industry has on the economy of an area and governments. For examples, governments tax petrol and so gain essential funding from crude oil.

67. Measuring the energy released by fuels CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Hydrocarbons as fuels
Hydrocarbons are mainly used as fuels as they release energy when they combust. Fuels burn when they react with oxygen in the air. If there is plenty of air, complete combustion happens based on the following reaction:
Fuel + Oxygen Water + Carbon Dioxide
Measuring the energy released by fuels
The energy released by a fuel can be measured using a simple experiment. Measuring heat transfers is called calorimetry. The diagram shows a simple calorimetry experiment to measure the heat energy released from burning fuel:
Model Question:
What are the two products released when a fuel combusts?
Model Answer
Carbon dioxide and water. Energy is also released.
CLICK to reveal MODEL ANSWER

68. CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Calculating the energy released by the fuel
The amount of energy released by the fuel can be calculated from the change in temperature of the water in the calorimeter. The following must be know:
The mass of the water heated
The temperature rise in the water.
The following equation can then be used to calculate the energy change:
Energy transferred (jolues/J) = Mass of the water heated (grams/g) x 4.2 x temperature
change(0C)
Model Question:
Calculate the energy released when 20g of water is heated by methane from 200C to 600C?
Model Answer
Energy released = 3,360J
Worked example of calculation of energy released by a fuel
30g of water is heated using butane. The water temperature rises from 250C to 550C. What is the energy transferred?
Energy transferred = 30 x 4.2 x (55-25)
= 3,780 J
CLICK to reveal MODEL ANSWER

69. CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Fire triangle
There are three key components that are required for a fire, they can be found in the fire triangle. When the three components are present a fire can quickly result. All methods of fire prevention use the idea of removing one of the three components in the fire triangle.
Before a fire can occur, three things must come together:
an ignition or heat source,
a fuel source (materials that burn)
Oxygen.
Model Question:
Explain how you would put out the following fire using the fire triangle:-
A forest fire
A chip pan fire
Model Answer
Remove the trees – remove the fuel or use large amounts of water – remove heat.
Cover in a damp cloth – remove the oxygen.
CLICK to reveal MODEL ANSWER

70. Laboratory method of cracking CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Cracking
Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful hydrocarbons. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst. Below is a diagram of the apparatus used in the laboratory to carry out this process.
Laboratory method of cracking
The larger hydrocarbon, paraffin is soaked into the mineral wool and heated. The porcelain chips act as the catalyst. The smaller hydrocarbons are collect in the boiling tube.
The large hydrocarbons are broken down into smaller hydrocarbons: alkanes and alkenes are made. The alkanes are used as fuels and the alkenes can be used to make polymers.
Model Question:
What is cracking?
Model Answer
The process by which a large less useful hydrocarbon is broken down into smaller more useful hydrocarbons.
CLICK to reveal MODEL ANSWER

71. CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Alkanes and alkenes are known as hydrocarbons. They are compounds that contain only hydrogen and carbon. The alkanes are part of a homologous series. This is a series of closely related compounds and can be described using a general formula. Alkanes are also hydrocarbons. They contain a single bond and have the general formula CnH2n The number of carbon give the name: One carbon is Meth, so when it is an alkane the a name is Methane.
Model Question:
If you had 15 carbons what would be the alkane formula?
Model Answer
C15H32
CLICK to reveal MODEL ANSWER

72. CLICK to reveal MODEL ANSWER
WJEC Crude oil part one   
Alkenes are also hydrocarbons. They contain a double bond and have the general formula CnH2n. The first two in this series are: ethane and propene. They are unsaturated and can take part in chemical reactions.
TESTING FOR ALKENES
You can use bromine water to work out if you have an alkene. Bromine water is orange. Alkenes decolourise the bromine water. Alkanes do not change the colour.
Model Question:
You have two solutions A and B, one is ethane and the other ethene. A gives no reaction with bromine water but B decolourises. Identify A and B.
Model Answer
A is an ethane and B is an ethene.
Ethene Propene
Alkene undergo an addition reactions with hydrogen and bromine.
CLICK to reveal MODEL ANSWER

73. Branched chain Isomers in alkanes
WJEC Crude oil part one   
Higher Only - Isomers
Isomers are compounds with the same molecular formula but different structures. Different arrangements are possible for all the alkanes except the first three members of the series.
You can see that in the first isomer there is four carbons in the chain and so is called butane. (but- means 4)
In the second isomer there is three carbons in the chain and one on the middle carbon. This is known as 2- Methyl-propane. This is because on the second carbon there is a methyl group (one carbon). The chain is then three carbons and so propane. (prop- means 3)
The two isomers have different structures and so different boiling points.
Branched chain Isomers in alkanes
In these isomers the carbon in the chain can alter. For example if you had C4H10 then you could arrange this in two ways, as outlined below:

74. AQA Crude oil and fuels - Questions What is crude oil?
What is a hydrocarbon?
What is an alkane?
4. Give the general formula of an alkane.
5. Complete the table.
Alkane
Number of Carbons
Number of Hydrogens
Formula
Structure
methane 1
ethane 6 3
6. What is fractional distillation?

75. 7. What are the products of combustion of a hydrocarbon?
8. What is cracking?
9. What is the general formula of alkanes?
10. How would you test for a double C=C bond?
11. What are the three components needed for a fire to occur?
12. Calculate the energy released when 35g of water is heated from 100C to 480C?
13. Draw the isomers for C5H12

76. CH4 C2H6 C3H8 AQA Crude oil and fuels - Answers
What is crude oil? A mixture of lots of different organic compounds. Formed from dead sea creatures over millions of years.
2. What is a hydrocarbon? A compound made of hydrogen and carbon only.
3. What is an alkane? Hydrocarbons with single C-C bonds.
4. Give the general formula of an alkane.CnH2n+2.
5. Complete the table.
Alkane
Number of Carbons
Number of Hydrogens
Formula
Structure
Methane 1 4
CH4
Ethane 2 6
C2H6
Propane 3 8
C3H8
6. What is fractional distillation? Heating crude oil to separate it into hydrocarbon fractions with different boiling points.

77. 7. What are the products of combustion of a hydrocarbon?
Carbon dioxide and water
8. What is cracking?
Breaking down a large less useful hydrocarbon into smaller, more useful hydrocarbons.
9. What is the general formula of alkanes?
CnHn+2
10. How would you test for a double C=C bond?
Add bromine water, if a double bond is present then the bromine water will be decoloured.
11. What are the three components needed for a fire to occur?
Fuel, oxygen and heat
12. Calculate the energy released when 35g of water is heated from 100C to 480C?
5,586J
13. Draw the isomers for C5H12

79. DTT Booster WJEC Chemistry THERAPY Topic - Crude oil part 2
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DTT Booster
WJEC Chemistry
THERAPY Topic - Crude oil part 2  
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

80. Conduction and convection
WJEC – Crude oil part 2 
Alkenes can be used to make additional polymers such as poly(ethene) and poly(propene). In these reactions, many small alkene molecules (monomers) join together to form very large molecules (polymers). This happens at very high pressure and temperature.
If you join many propene molecules you get poly(propene). If you join many styrene molecules you get poly (styrene).
Model Question: Draw the structure that this monomer will make.
Model Answer
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

81. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2 
Polymer
Typical use
Repeating unit
Poly(ethene)
plastic bags and bottles
Poly(propene)
crates and ropes
PTFE
Non-stick coating on saucepans
Poly(chloroethene)
PVC
water pipes and insulation on electricity cables
Model Question:
Why are polymers more useful than the monomers they are made from?
Model Answer
They have different properties than the monomers.
The long chains make them useful for making many different plastics.
CLICK to reveal MODEL ANSWER

82. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Thermoplastic polymers soften when heated and can be shaped when hot. Poly(ethene) is a thermosoftening polymer.
Model Question:
Water bottles can be heated and re-shaped. Can you explain which type of plastic they are made out of and why you think this?
Model Answer
Thermoplastic
Can be softened by heat and so can be re-shaped.
Can not be thermosetting plastic as they can not be softened upon heating.
CLICK to reveal MODEL ANSWER
Thermosetting polymers have different properties to thermoplastic polymers. Once moulded, they do not soften when heated and they cannot be reshaped. This is due to the polymer chains being joined together by cross-links, so they cannot slide past each other easily.

83. Plastics and the environment CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Properties and use of Plastics
Plastics have a number of different properties:
Resistant to corrosion
They can be moulded and shaped
Some are resistant to heat
They can be coloured
Flexible
Electrical and heat insulators
Low density
Do not absorb water
Plastics and the environment
Plastics will not break down in the environment. They are non-biodegradable. This means that they will be around for hundreds of years even after they have been used. Think about your pen; it will still be here when you’re in your nineties! This causes problems with disposal of the waste and many landfill sites are fast becoming full due to the number of materials, which will not break down. It is not possible to simply burn them, as many plastics give off toxic fumes.
The Welsh Government has introduced a charge of 5p for bags to try to get people to use fewer plastic bags.
Model Question:
Explain how plastic bags can have a negative effect on animals.
Model Answer
Animals can either eat them and this causes digestive problems or become entwined in them.
CLICK to reveal MODEL ANSWER

84. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Fermentation
The fermentation of fruits which contain sugar has been known for thousands of years. Yeast occurs naturally and is sometimes found on the skin of fruit. The enzymes in yeast slowly convert the sugar to a weak alcoholic mixture. This is done in industry on a massive scale. Beer and wine is made in this way.
Test for alcohol
The presence of an alcohol group can be tested for by using acidified potassium dichromate. The acidified potassium dichromate is orange and when added to an alcohol it changes to green upon gentle heating in a water bath.
Model Question:
What are the products of fermentation and how could you test for it?
Model Answer
The products are ethanol and carbon dioxide. The test for ethanol uses acidified potassium dichromate, which turns from orange to green.
Carbon dioxide gas bubbles out of the solution into the air leaving a mixture of ethanol and water. Fermentation must be carried out in the absence of air to make alcohol. Ethanol can be separated from the mixture by fractional distillation
CLICK to reveal MODEL ANSWER

85. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Uses of Ethanol
In alcoholic drinks
Yeast is used in a batch process to make alcohol in beer and wine. An enzyme in yeast acts on the natural sugar in malt (to make beer) and grapes (to make wine). When the alcohol concentration reaches about 10%, the alcohol damages the yeast and fermentation stops. Alcohol in drinks is measured in units. Different drinks have different amounts of ethanol present in them.
As a Solvent
Ethanol is a solvent in many cosmetics for example, aftershaves and nail varnish. The ethanol evaporates quickly.
As a Fuel
Ethanol can be made on a large scale for use as a fuel or solvent by the hydration of ethene or the fermentation of sugar cane. Sugar cane is a renewable resource. Renewable means that the resource can be replaced. For example more sugar cane can be grown. Biofuels are carbon neutral, which means that they release only as much carbon dioxide as the plant took in by photosynthesis. This helps to reduce global warming.
However, some people are concerned about whether it is ethical to use food crops in this way, instead of using them to feed hungry people. Also the amount of land needed to produce the crops is huge.
Model Question:
What is a biofuel?
Model Answer
A fuel made out of living materials, such as sugar cane or wood.
CLICK to reveal MODEL ANSWER

86. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Issues with alcohol.
Social
Ethanol is a depressant - it slows down signals in the nerves and brain. Small amounts of alcohol help people to relax, but greater amounts lead to a lack of self-control and loss of judgement. Drinkers may put themselves in dangerous situations, and may not realise how much they are drinking. They may fall ill, or become unconscious.
People suffering from 'hangovers' after drinking alcoholic drinks may be unable to function normally the next day. This puts strain on their family and their colleagues, and can lead to family problems, lost work and missed business.
Health issues
Ethanol causes damage to the liver, and leads to a risk of stroke or heart disease. This causes problems both for the drinker, and for those around them. Such diseases require the resources of the Health Service, which means it has less to spend on treating other illnesses.
Other alcohol-related problems include:
accidents caused by people who drive or use machinery while drunk
vandalism, fighting and other forms of anti-social behaviour
family violence and breakdown
Model Question:
Name one disease associated with excess alcohol consumption?
Model Answer
Stroke, heart disease, liver disease
CLICK to reveal MODEL ANSWER

87. Ethanol to Ethanoic acid CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Ethanol to Ethanoic acid
When ethanol reacts with oxygen it forms a weak acid called ethanoic acid. This can happen naturally in the presence of bacteria, and it is the ethanoic acid which can make beer or wine taste sour.
ethanol + oxygen ethanoic acid + water.
C2H5OH(aq) + O2(g) CH3CO2H(aq) H2O(l)
Ethanoic acid is a weak acid. It is found in vinegar ("vinegar" is Old French for "sour wine"). Vinegar is used as a food flavouring and preservative.
Model Question:
Explain what would happen when wine is left open to the air?
Model Answer
If wine is left on the side then the ethanol in it would react with the oxygen in the air and oxidise. The ethanol would turn it into ethanoic acid.
CLICK to reveal MODEL ANSWER

88. CLICK to reveal MODEL ANSWER
WJEC – Crude oil part 2  
Example:
You can use simple spectra's to identify the organic functional group. For example the spectra below contains the stretching frequencies for alcohol at 3300cm-1. This can be used to identify it within a organic compound.
Spectroscopy
Analytical chemist’s can use a range of methods to identify different substances in water, blood and other liquids. One of these methods is called Atomic Spectroscopy. It can be used to find the concentrations of atoms or ions within a sample. It can be used to detect the present of certain organic functional groups:
Alkanes – ethane
Alkenes - ethene
Alcohols - ethanol
Carboxylic acid – ethanoic acid.
Model Question:
If you had ethanol what frequency would you see it on a spectra?
Model Answer
At 3300 cm-1
CLICK to reveal MODEL ANSWER

89. Polymerisation and Polymers - Questions
1. Draw a diagram representing the process of polymerisation of ethene. Label the following: Monomer Polymer Ethene Poly(ethene) 2. What conditions are needed for polymerisation to occur? 3. What is poly(ethene) used for? 4What is PVC used for? 5. Explain why thermosetting plastic can not be softened when heated? 6. What test is used to determine if a chemical is an alkene?

90. Polymerisation and Polymers - Questions
7. How can alcohol be produced using yeast? 8. What is the chemical test for an alcohol? 9. Give the three main uses of alcohol? 10. Outline two negative affects of large consumption of alcohol? 11. Explain a disadvantage of using biofuels? 12. How is ethanoic acid produced/ 13. What is spectroscopy?

91. Polymerisation and Polymers - Answers
Draw a diagram representing the process of polymerisation of ethene.
2. What conditions are needed for polymerisation to occur? High temperature and high pressure.
3. What is poly(ethene) used for? Making plastic bags, food containers and bottles.
4. What is PVC used for? Window frames, water pipes and electrical insulation for cables.
5. Explain why thermosetting plastic can not be softened when heated?
Cross-link between the polymer means they can not be softened.
6. What test is used to determine if a chemical is an alkene? Bromine water if it goes clear then the chemical is an alkene.

92. Polymerisation and Polymers - Questions
7. How can alcohol be produced using yeast? Ethanol and carbon dioxide 8. What is the chemical test for an alcohol? Add orange acidified potassium dichromate and it will go green in the present of alcohol. 9. Give the three main uses of alcohol? Solvent, fuels and alcoholic drinks. 10. Outline two negative affects of large consumption of alcohol? Social issues and health issues 11. Explain a disadvantage of using biofuels? Large amount of land required for the sugar cane and takes land that could be used for food. 12. How is ethanoic acid produced? Leaving ethanol out in air. 13. What is spectroscopy? Method used to identify organic compounds based on their functional groups.

93. DTT Booster WJEC Chemistry
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DTT Booster
WJEC Chemistry
THERAPY WJEC – 2.6 Reversible Reactions, Industrial Processes and Important Chemicals   
Commissioned by The PiXL Club Ltd. February 2016
© Copyright The PiXL Club Ltd, 2016
This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school.
All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution.
The PiXL Club Ltd, Company number

94. What is a reversible reaction?
WJEC 2.6 Reversible Reactions and Industrial Processes
What is a reversible reaction?
A reversible reaction is one where the products can turn back into reactants. The reaction can go both ways.
Reversible reactions are shown using an arrow like the one above.
Not all reactions are reversible but there are some important examples that occur when important chemicals are made.
Model Question
How would the reaction below be written differently if the reaction was reversible?
CLICK to reveal MODEL ANSWER
Model Answer

95. CLICK to reveal MODEL ANSWER CLICK to reveal MODEL ANSWER
WJEC 2.6 Reversible Reactions and Industrial Processes
The Haber Process
Model Question
What are the conditions used to make ammonia in the Haber process?
Model Answer
250 atmospheres.
450°C
Iron catalyst
Ammonia, NH3, is formed in the Haber Process from nitrogen and hydrogen. The reaction is reversible.
Learn the equations.
CLICK to reveal MODEL ANSWER
CLICK to reveal MODEL ANSWER
The Conditions Used
250 atmospheres.
450°C
Iron catalyst

96. CLICK to reveal MODEL ANSWER
WJEC 2.6 Reversible Reactions and Industrial Processes
Nitrogen
(from the air) 1
250 atmospheres
450°C
Passed over beds of iron
Gases are cooled and ammonia turns to a liquid
Hydrogen
(from natural gas) 3
Unreacted nitrogen and hydrogen are
recycled and pass through again
Liquid ammonia collected
Model Question
What happens to the nitrogen and hydrogen that does not react?
Model Answer
The unreacted nitrogen and hydrogen are recycled and go through the process again. This gives them more chances to react and saves money as less hydrogen and nitrogen has to be produced.
CLICK to reveal MODEL ANSWER

97. Conduction and convection
WJEC 2.6 Reversible Reactions and Industrial Processes
Reaction Conditions - HT
Model Question
What would be ideal conditions for the highest yield of ammonia.
Model Answer
Very high pressure and a low temperature.
CLICK to reveal MODEL ANSWER
The conditions used are a compromise.
Lower temperatures give higher yield but are slow.
Higher pressures give higher yields but are dangerous and it is expensive to run the process at high pressures.
P1.1.3a/P1.1.1

98. Conduction and convection
WJEC 2.6 Reversible Reactions and Industrial Processes
Making Sulfuric Acid
The Contact Process
Important Points
Stage 2 is reversible.
Conditions for Stage 2 are:
Pressure = 1 atmosphere
Temperature = 450°C
Catalyst = vanadium(V) oxide
In Stage 3, SO2 is not added to water directly. It is added to concentrated H2SO4 to make it more concentrated.
Sulfuric acid is made in a 3 stage process:
Stage 1:
Sulfur is burned to make sulphur dioxide.
S + O2 SO2
Stage 2:
Sulfur dioxide is reacted with more oxygen to form sulphur trioxide.
2SO2 + O2 2SO3
Stage 3:
Sulfur trioxide is reacted with water to make sulphuric acid.
H2O + SO3 H2SO4
Model Question
Which part of the conact process is reversible?
Model Answer
The stage where sulphur dioxide is reacted with oxygen to make sulphur trioxide.
CLICK to reveal MODEL ANSWER
P1.1.3a/P1.1.1

99. Conduction and convection
WJEC 2.6 Reversible Reactions and Industrial Processes
Uses of Sulfuric Acid
Sulfuric acid can remove water from sugar molecules to leave carbon.
Sulfuric acid can remove water from blue copper(II) sulfate crystals to leave white anhydrous copper sulfate.
an = without; hydrous = water (hydrate)
Millions of tonnes of sulphuric acid are made every year. It is used to make a wide variety of products.
Model Question
Why can sulphuric acid be described as a dehydrating agent?
Model Answer
Sulfuric acid can remove water from some molecules.
CLICK to reveal MODEL ANSWER
Sulfuric acid can react with some substances and remove water from them. When it does this, sulphuric acid is acting as a dehydrating agent.
P1.1.3a/P1.1.1

100. Conduction and convection
WJEC 2.6 Reversible Reactions and Industrial Processes
Fertilisers
Model Question
Describe eutrophication.
Model Answer
Fertilisers get washed into rivers and streams.
Algae grow very quickly.
The algae cuts out light beneath it.
Plants die and decompose.
There is less oxygen in the water. Plants and animals die.
Plants need different nutrients to grow. We can make fertilisers on a massive scale to help grow enough food for everyone to eat.
Ammonia is used as it contains nitrogen which is very important for plants.
CLICK to reveal MODEL ANSWER
Advantages of fertilisers
Disadvantages of fertilisers
Grow more crops
Eutrophication
Make more money
Plants low in nutrients
Feed more people
Blue baby syndrome
In the reactions above the ammonia is neutralising the acid: it is a base.
P1.1.3a/P1.1.1

101. Testing for NH4+ Compounds CLICK to reveal MODEL ANSWER
WJEC 2.6 Reversible Reactions and Industrial Processes
Model Question
How do you test a compound to see if it contains NH4+?
Model Answer
Dissolve. Add sodium hydroxide and warm.
Hold damp red litmus above the tube.
A NH4+ compound turns litmus blue.
Testing for NH4+ Compounds
CLICK to reveal MODEL ANSWER
In the reaction below, ammonia gas, NH3, is given off. Ammonia is an alkali and turns litmus blue. This is the test for ammonia gas.

102. WJEC 2.6 Reversible Reactions and Industrial Processes
What is a reversible reaction?
Write a word and symbol equation for the formation of ammonia.
Give the conditions used to make ammonia in industry.
What is the test for ammonia gas?
Write symbol equations for the stages in the Contact Process.
Give 3 uses of sulphuric acid.
Write a word equation for the formation of ammonium sulfate.
Why are artificial fertilisers important?

103. WJEC 2.6 Reversible Reactions and Industrial Processes
What is a reversible reaction?
A reaction where products can turn back into reactants.
Write a word and symbol equation for the formation of ammonia.
nitrogen + hydrogen ammonia N2 + 3H NH3
Give the conditions used to make ammonia in industry.
250 atmospheres 450°C Iron catalyst
What is the test for ammonia gas?
It turns damp red litmus blue.
Write symbol equations for the stages in the Contact Process.
S + O SO SO2 + O SO SO3 + H2O H2SO4

104. 6. Give 3 uses of sulphuric acid.
Dye paint fertilisers fibres plastics detergents
7. Write a word equation for the formation of ammonium sulfate.
Ammonium hydroxide + sulphuric acid ammonium sulfate + water
Why are artificial fertilisers important?
They increase crop yields which means that more people can be fed and generates more money for farmers.