1. Chemistry Unit 2 Revision & Exam Preparation
Plymstock School
P.J.McCormack

2. The Scooby Doo Analogy What is the story line in Scooby Doo?
24 June, 2019
The Scooby Doo Analogy
What is the story line in Scooby Doo?
How is this relevant to revision?
P.J.McCormack

3. Specification and Past Papers (hyperlinked)
24 June, 2019
Specification and Past Papers (hyperlinked)
P.J.McCormack

4. 24 June, 2019
Chemistry Unit 2 Topics.
C2.1 – Structure & Bonding C2.2 - How structure influences the properties and uses of substances C2.3 - Atomic structure, analysis and quantitative chemistry C2.4 - Rates of reaction C2.5 - Exothermic and endothermic reactions C2.6 - Acids, bases and salts C2.7 - Electrolysis
P.J.McCormack

5. Useful Websites Knock Hardy http://www.knockhardy.org.uk/gcse.htm
24 June, 2019
Useful Websites
Knock Hardy
Doc Brown
Creative Chemistry
AQA Past Papers
AQA Chemistry Specification
P.J.McCormack

6. 24 June, 2019
Creating Flashcards
An independent revision technique.
P.J.McCormack

7. C2 Chemistry NANO-TECHNOLOGY OIL RIG Ionic Bonding Electrolysis:
e.g. Water, Cl2, H2, HCl CH4, O2
Diamond
Delocalised electrons
Giant Covalent Structure
High melting and boiling points, hard
Strong covalent bonds
Simple molecules
Low melting and boiling points
Weak intermolecular forces
Does not conduct electricity
Graphite only:
Conducts electricity, soft
and slippery between layers.
C2 Chemistry
Covalent Bonding
Non-metals sharing elections
No charge
An atom:
Number of Protons = Number of Electrons
Mass number = Protons + Neutrons
Periodic table arranges elements by ATOMIC NUMBER (proton number/the small one)
OIL RIG
Oxidation is lose (of electrons)
Reduction is gain (of electrons)
Pure copper
Impure copper
(copper ore)
Max 2 electrons
Max 8 electrons
E.g. 2,8,8 (Argon)
The number of outer shell electrons match the group the element is found in.
E.g. Lithium 2,1 is a group 1 element.
Cu 2+
Describe this!
Copper purification
Impurities: include gold and silver (can be sold)
Protons and neutrons both have a mass of 1
ISOTOPES
are atoms of the same element with different numbers of neutrons
Electrolysis:
Splitting up a substance using electricity
Metallic Bonding
Sea of delocalised electrons
Can carry a charge so metals conduct electricity
Half equations
Electrolysis needs:
2 electrodes
An electrolyte
(Ionic or molten substance)
A power supply
Ions move toward oppositely charged electrodes
Ionic Bonding
When there are 2 possible products
The less reactive forms at the electrode
Lose or gain an electron
Get a charge +/-
Attract one another!
Used for: Disinfectants, bleach and plastics
Metal ions only arranged in layers
ELECTROSTATIC ATTRACTION between
+IONS and ELECTRONS
Group 1
Group 7
Brine:
Salt water
Used for: Margarine and HCl
Electrolysis of Brine
Metal ions slide over one another making them MALLEABLE
Metals conduct HEAT well
Used for: Bleach, paper and soap
Giant Lattice Structure
Always metals with non-metals
+ ION and – ION attracted by STRONG ELECTROSTATIC FORCES
As a solid: High melting and Boiling Point
Conducts electricity when melted or dissolved:
Ions move freely and carry a charge
NANO-TECHNOLOGY
Means REALLY REALLY REALLY small !!!!!

8. When a reaction forms a SOILD(s) its called a PRECIPITATE
Low temperatures will increase the yield of exothermic reactions.
High temperatures will decrease the yield of exothermic reactions.
If temperature are too low a reaction will be too slow.
Relative formula Mass
Add the mass of each atom in the formula together
e.g. CaCO3
= 100
Exothermic reactions give out heat to the surroundings(get hotter)
We compare the mass of any atom to Carbon 12
If temperatures are too low a reaction will be too slow.
Moles
1 mole of any substance
contains the same number of particles (6.02x1023)
Relative atomic mass or formula mass in grams is equal to one mole.
e.g. 12g of carbon is one mole of carbon
Endothermic reactions take in heat from the surroundings (get colder)
Mass of element
Total mass of compound x 100 = Percentage Mass
e.g. % mass of carbon (12) in ethane C2H6 (30)
24 / 30 x 100 = 80%
Increasing pressure will increase the yield on the side with less molecules.
BUT
High pressures are expensive.
Reversible Reaction
One way will be endothermic and the other will be exothermic
In a closed system forward and backward reaction occur at equal rates
All the carbon ( = 24)
Make sure you can explain this in reverse!
Too removed a solid (s) from a reaction you FILTER it out !
e.g. Respiration & Combustion
If you reaction gives you a dissolved product (aq) instead, you EVAPOURATE it out !
When a reaction forms a SOILD(s) its called a PRECIPITATE
Acid + Metal Salt + Hydrogen
Acid + Base Salt + Water
e.g. Photosynthesis
We can measure the rate of a reaction by looking at how fast solid reactants are used up, how quickly gas is produced or how quickly light is blocked (the disappearing cross)
e.g. Sulfuric Acid + Magnesium -> Magnesium sulfate+ Hydrogen
Collision Theory
e.g. Nitric Acid + Copper Oxide -> Copper nitrate + Water
The rate of a reaction is speed up by increasing the:
Temperature
Surface area
Concentration
Or by adding a CATALYSIS
Acid
Salt
Hydrochloric Acid
Chloride
Sulfuric Acid
Sulfate
Nitric Acid
Nitrate
For this:
Anything that's not a metal on its own is a base
When we increase the concentration/surface area we increase the frequency of particles colliding and reacting. Speeding up the reaction.
When we increase the temperature the particles move faster, they are more likely to collide and do so with sufficient energy to react. Speeding up the reaction.
Catalysts speed up reactions without being used up
IMPORTANT
Acids & Bases (Alkalis)
Increase in pressure is the same as increase in concentration
Acids – H+
Alkalis – OH-
An increase of 10oC doubles the rate of a reaction
For a reaction to take place we have to have the minimum amount of energy needed
The ACTIVATION ENERGY
Bases NEUTRALISE acids
Alkalis are soluble bases
pH Scale
Find the pH using Universal Indicator

9. Balanced Equations Molecular Formula & Empirical Formula
Molecular Formula : The actual number of atoms of each element in an individual molecule
Empirical Formula : The simplest whole number ratio of the elements in the molecule
Calculating the Empirical Formula
1) Use the same table and method given for calculating reacting masses but remove the ratio row.
The question will either provide the grams of each element or the percentage. Assume percentages are the same figure in grams.
e.g. 12% = 12g
Percentage Yield
This is used to compare our actual yield with our theoretical yield.
Amount of product actually produced
Maximum possible yield (Theoretical yield) x 100
e.g. 200
275 x = %
Its rare to get 100% yield
This is because some products can be left in apparatus or separating products from reactants is difficult.
Sometimes it’s not everything reacts to begin with.
A balanced equation has the same number of atoms for each element on both sides
We can use this to find the ratio of moles that are needed to react with one another
e.g. 1 CH4 molecule reacts with 2 O2 molecules
1:2 ratio
Atom Economy
This calculates the amount of starting material that ends up as useful products
The aim is always for the highest atom economy possible
Formula mass of useful products
Formula mass of all products x 100
e.g
( ) x = 55 %
High atom economy conserves resources, reduces pollution and maximises profits
Question: A substance contains 24% carbon and 64% hydrogen. Calculate the its empirical formula.
When doing an experiment if we know the grams used and the Molecular/Formula Mass we can calculate the moles
e.g. In 24 g of carbon which has an Mr of 12 there would be 2 moles of carbon.
24/12 = 2
This is useful if we want to calculate how much product we would get from a specific amount of reactant
THEORETICAL YIELD g
Grams
Chemical
Carbon
Hydrogen
Grams 24 64 Mr 12 16
Moles 2 4 n
Moles Mr
Molecular/
Formula Mass
Calculating Theoretical yield
Question: How much CO2 would be produced by burning 100g of
Methane (CH4) ?
2) To get the simplest ratio divide all moles by the smallest calculated value
2/2 = /2 =
1 : 2
This gives you the number of each element present and the empirical formula
C H2
Chemical
CH4
CO2
Ratio 1
Grams
100 ? Mr 16 44
Moles
6.25
4) Now you have the Mr and the moles of CO2 you can use the triangle to calculate the grams that will be produced.
44 x = 275
Answer: 100g of methane would make 275 g of CO2
1) Put in the things you already know. You were given the grams of methane in the question. And can calculate the Mr using the periodic table.
2) Use the triangle to calculate the moles or methane used.
All figures in example calculations refer to the burning of methane in oxygen as shown in the balanced equation
If you were told the compound had a mass of 28 you could calculate the molecular formula
The Mr of CH2 is 14
28 /14 = 2
Therefore the molecular formula must be double the empirical one C2H4
3) Use the ratio from balanced equation to provide the moles of CO2
1 : : 6.25

10. C2.1 – STRUCTURES & BONDING
Draw the symbol for sodium include its mass number and atomic number (what do they tell us)
Complete the table
Use pictures and words to describe each type of bonding:
Ionic
Covalent
Metallic
Relative Charge
Relative Mass
Proton
Neutron
Electron
Fill in the table to show the number of electrons that can fit into the shell
Draw and write the electronic configuration for:
Sodium
Argon
Shell
Max. Electrons 1 2 3
What happens to the shells as you:
Go across a period
Go down a group
KEY WORDS:
Electron
Proton
Neutron
Shell
Electronic Configuration
Covalent/Ionic/Metallic
ASSESSMENT:

11. C2.2– STRUCTURES & PROPERTIES
IONIC COMPOUNDS What type of force holds the ions together?
Draw a giant ionic lattice:
Why do ionic compounds have high melting and boiling points?
Why can ionic compounds conduct electricity when molten or dissolved in water?
SIMPLE COVALENT MOLECULES How strong are the forces between covalent molecules? [intermolecular forces]
How does this affect their melting and boiling point
How strong are the forces between atoms in a covalent bond? [intramolecular bonds]
GIANT METALLIC SUBSTANCES Why can metals be bent and shaped?
What are delocalised electrons?
Why do metals conduct electricity?
GIANT COVALENT SUBSTANCES Name 3 of these substances:
Why is graphite slippery and conduct electricity
KEY WORDS:
Diamond
Graphite
Intermolecular
Intramolecular
Delocalised
ASSESSMENT: 12

12. C2.3 – Atomic Structure, Analysis and Quantitative Chemistry
Write how many there are in:
Na11
Electrons:
Protons:
Neutrons:
What is an isotope?
What is Ar?
What is Mr?
What is the Mr of C2H5OH?
What is a mole?
Balance the equation and say how many moles of each substance there are:
H O2  H2O
What is percentage yield and what is the equation to calculate it?
What is atom economy and what is the equation to calculate it?
What is the symbol for a reversible reaction?
Explain what happens after we add just reactants to a reversible reaction? [HIGHER TIER] 23
What is the Haber process?
What are the raw materials?
What is the reaction equation?
What conditions are required?
KEY WORDS:
Reversible
Haber Process
Relative Atomic Mass
Relative Formula Mass
Isotope
Moles
ASSESSMENT: 13

13. C2.4 – RATES OF REACTION 14 What do we mean by ‘rate of reaction’?
What 4 factors affect the rate of a reaction?
What must happen for a reaction to occur?
What is the smallest amount of energy that must be overcome for a reaction to occur?
How does surface area affect rate of reaction?
Explain the effect of temperature on the rate of reaction [think about: kinetic energy & number of collisions]
Draw diagrams to represent it:
Explain the effect of concentration on the rate of reaction
Draw diagrams to represent it?
Low concn
High concn
What do catalysts do?
What happens to them during a reaction?
Low temp
High temp
KEY WORDS:
Collision Theory
Catalyst
Activation Energy
Rate of Reaction
Concentration
Temperature
ASSESSMENT: 14

14. C2.5 – Exothermic and Endothermic Reactions
What are exothermic reactions?
Give an example and explain why it is exothermic?
What are endothermic reactions?
Give an example and explain why it is endothermic
If a reaction is exothermic how can we increase yield?
Why do we settle for a higher than expected temperature in the Haber process?
If a reaction produces a smaller volume of gases how can we increase yield?
Why do we have to compromise with a lower than expected pressure in the Haber process
What can you say about energy in a reversible reaction? [Think: exo and endothermic]
Describe the anhydrous copper sulphate reversible reaction
What can anhydrous copper sulphate be used to test for?
KEY WORDS:
Collision Theory
Catalyst
Activation Energy
Rate of Reaction
Concentration
Temperature
ASSESSMENT: 15

15. C2.6 - ACIDS, ALKALIS & SALTS
What is a base?
What is an alkali
What ions make something acidic?
What is another name for an acid? P__________ D__________
What ions make something alkali?
What is the pH scale?
What is produced when an acid and a metal react?
Acid + Metal 
Give a specific example:
What is produced when an acid and an alkali react? Acid Alkali 
What type of reaction is this called?
How can this reaction be simplified using just the ions involved?
What is a precipitation reaction?
How can we make ammonium hydroxide?
What happens when we add nitric acid to it?
What is produced when an acid and a base react?
Acid + Base 
Give a specific example:
Describe 2 uses for acids and alkalis in the ‘real world’
KEY WORDS:
Acid
Base
Alkali
pH scale
Indicator
Precipitate
ASSESSMENT: 16

16. C2.7 – ELECTROLYSIS 17 What is electrolysis?
What do we call the substance that is broken down during electrolysis
What is the positive electrode called?
What is the negative electrode called?
Label a diagram showing the electrolysis of copper bromide
What ions are formed?
How is the electrolysis of copper different? [Draw a diagram to help]
What 3 products are made when we electrolyse brine? Give a use for each?
What does OILRIG stand for?
Describe the movement of ions and electrons at each electrode when potassium iodide is electrolysed
What happens when we carry out electrolysis in water?
KEY WORDS:
Electrolysis
Cathode
Anode
Oxidation
Reduction
ASSESSMENT: 17

17. Why should you revise?
Your brain forgets details of the work you did months ago,
But…
You need these details to answer the questions in the exam,
So…
You need to ‘top-up’, by using the correct revision technique.

18. Where should you revise?
In a quiet room, perhaps a bedroom,
Warm and well-lit,
With a table to work at,
Ideally, with a table-lamp, to help you to focus on the page,
With a clock for timing (as described later).

19. Where should you revise?
What’s wrong with this?

20. Where should you revise?
What is better here?

21. When should you revise? Start your revision early each evening,
before your brain gets tired.

22. How should you revise? If you just sit down to revise,
without a definite finishing time,
then your learning efficiency
falls lower and lower,
like this:

23. How can you improve this?
If you decide at the beginning
how long you will work for, with a clock,
then as your brain knows the end is coming,
the graph rises towards the end

24. How can you improve this even more?
If you break up a 2-hour session,
into 4 shorter sessions,
each of about 25-minutes,
with a short planned break between them,
then it is even better.
Compare the next 2 graphs:

25. One solid session
4 shorter sessions
The yellow area shows the improvement.

26. For example,
Suppose you start work at 6 pm.
You should decide, looking at your clock or watch, to stop at 6.25 pm --and no later.
Then at 6.25 pm have a break for 5-10 minutes.
When you start again, look at the clock and decide to work until 7 pm exactly, and then have another break.
This way, you are working more efficiently, as the previous slide showed.

27. How often should you revise?
Look at the graph below:
It shows how much your brain can recall later.
It rises for about 10 minutes …and then falls.

28. However,
if you quickly re-revise after 10 minutes,
then it falls more slowly! This is good.
Analyse the new graph:

29. Even better,
if you quickly re-revise again, after 1 day,
then it falls even more slowly! Good !
Analyse the new graph:

30. And even better still,
if you quickly re-revise again, after 1 week,
then it falls even more slowly! Great!
Analyse the new graph:

31. 10 minutes 1 day 1 week …and then 1 month.
So the best intervals for ‘topping-up’,
by reviewing or briefly re-revising
are:
10 minutes
1 day
1 week
…and then 1 month.