Welcome to the Chemistry Department at Reigate College.
My name is Emma Nye and I’m Head of Chemistry A Level. Studying Chemistry at A Level is both challenging and fascinating so I’m really pleased you’ve chosen to take the course here at Reigate College. I’m looking forward to meeting you and welcoming you to the department in person at the beginning of the academic year.
To make sure you’re prepared for the course, I’d like you to complete a series of tasks and activities over the coming months. These activities will give you a better idea of the kinds of things you’ll be studying and the skills you’ll develop over the two years. Each task should be completed on your own, but there’ll be the chance to discuss what you’ve learnt with your fellow Chemists in September.
All the tasks should be completed by Choices Day on 25 August. Please enjoy delving deeper into different aspects of the subject.
The tasks will be released here in three phases:
Explore your Subject – 4 May
The Following tasks
and activities are designed to start preparing you for Chemistry A Level. They should be completed by 1 June.
The Chemistry of Fireworks
Chemistry has many uses in everyday life, some applications
are not as visible as others but fireworks are a really obvious way that we can
see chemistry at work.
How much do you actually know about the chemistry behind
Watch the following clip to find out more about how
fireworks use chemistry.
The graphic below summarises how fireworks work and how you can determine the colour a firework will be, based on the salt used.
Fireworks have a really obvious visual and sound effect that
everyone can easily see, but as chemists, one of the most important skills you
will develop is understanding what is happening at the atomic and molecular
level, i.e. what you can’t see.
You will already have an understanding of what is happening
in terms of atoms and molecules because at GCSE you will have learnt about
atomic structure. The easiest way to
show atomic structure is through dot and cross diagrams.
Dot and Cross Diagram
Refresh your memory about dot and cross diagrams by having a
go at drawing the following ionic salts that could be used in fireworks.
PLEASE NOTE: Please jot all your answers (for q1-12) into a note book and bring them with you to your first chemistry lesson of the autumn term.
1. Calcium Chloride CaCl2 (Remember this is an ionic compound)
2. Barium Chloride (This one is also ionic, make sure you have the correct formula before you start)
3. Can you draw a dot and cross diagram for Strontium Carbonate SrCO3?
[The carbonate ion CO3 2-, is covalent
in structure, see if you can work out what it will look like, if you get stuck,
look it up!]
4. Magnesium, Aluminium and Titanium are also used in their metallic form to give silver and white fireworks. Draw a simplified diagram of metallic bonding.
Flame Test Tasks
The reason you see the colours you do when the salts in the
fireworks are ignited is all to do with the atomic structure of the ions. You should have carried out flame tests at
GCSE and you should know that certain metal ions give a specific colour flame
that can be used as a test for the ion but do you know what is happening at the
atomic level to give these coloured flames?
The following link is to a really useful A Level resource
called Chemguide. It summarises how to
carry out a flame test but also explains why you see the distinctive colours
for metals when you carry out a flame test.
5. Read through this webpage above and then copy out the diagram below and annotate it to explain why sodium has a yellow flame.
The Burning of Black
Fireworks require fuels to be burnt to supply the energy required to excite the electrons from their ground state.
This is not a simple combustion reaction as you can’t see
the oxygen. The Potassium Nitrate is the
oxidiser, in this instance. We can determine how much energy we will get from a
mole of a fuel by carrying out a simple experiment. Combustion is an exothermic reaction (heat is
lost from the system) and so heat is released to the surroundings and can be
used to heat water.
The apparatus below can be set up to measure the energy transferred to water by burning a liquid fuel like hexane.
6. Write a balanced chemical equation for the complete combustion of hexane.
Enthalpy change is measured in kJ/mol written as kJmol-1.
The moles in this case are the moles of the fuel you have burnt to get a
certain increase in temperature of the water.
We can use the following equation to calculate the energy
transferred to the water when we burn hexane:
Q = mcΔT
Q is the energy transferred to the water in J
m is the mass of the water
c is the specific heat capacity of water which is 4.18 J K-1
ΔT is the temperature change of the water
7. What equation would we need to use to calculate the number of moles of hexane burnt?
8. If 1.50g of hexane is burnt calculate the number of moles burnt.
9. If you have 100cm3 (or 100g) of water in the calorimeter and your initial water temperature is 22oC and your final water temperature 35oC, calculate the energy transferred to the water Q.
Your value of Q is in J, convert it to kJ.
10. Calculate the enthalpy change in kJmol-1 using your value of Q in kJ and divide it by the number of moles of hexane burnt. This enthalpy change will be negative as the reaction is exothermic.
This value is the enthalpy change of combustion for hexane.
This tells us how much energy we can expect to get from 1 mole of hexane, this
is useful because it allows us to compare one fuel with another.
The colour of a flame can give us a useful test for metal
ions, however, if you pass the light emitted from the flame through a prism or
diffraction grating you can get even more information about the wavelengths of
light emitted by an atom. This is an
analytical technique that can be very useful and is called spectroscopy.
11. Research how emission and adsorption spectra can be generated and how they can be used to identify unknown elements.
Other types of spectroscopy also involve the absorption of
energy being used as an identification technique. One such type of spectroscopy is Infrared
Spectroscopy, instead of electrons absorbing energy, this time it is bonds that
absorb it and this results in bonds stretching and bending. Infrared spectroscopy
allows us to identify the functional groups present in molecules which is a
very useful tool for identifying unknowns.
12. Find out more about how Infrared spectroscopy works and how it can be used, starting with the link below.
For the ‘Explore your Subject’ tasks we started looking at
what’s happening in molecules at atomic level.
For your ‘Get Going’ tasks we’re going to look at molecules, with a
focus on organic molecules.
Please complete these tasks by 1 July.
You should record your answers in a Word document and bring them with you at the beginning of term. If you don’t have access to a PC then please just write your answers into a note pad, and bring that with you instead.
Organic molecules are those which contain carbon. Organic molecules can be grouped together by
their functional groups which, in turn, give us a homologous series.
1. Write down a definition for a homologous series.
2. Using your GCSE knowledge, create two summary sheets that summarise your knowledge of Alkanes and Alkenes. The summaries should include the following information:
Names, formula and full structural formula (a drawing showing all of the atoms and bonds) for the first 10 members of the homologous series
Properties e.g. solubility, trends in boiling points as the molecules get longer etc.
Reactions that the homologous series undergo e.g substitution or addition reactions
A simple test to tell the difference between alkanes and alkenes
3. Another homologous series that you will need to know for A Level is the alcohols. Create a summary for alcohols like your alkane and alkene one above. If you have not come across alcohols in Chemistry before, then read through pages 1, 2 and 3 of the link below and then create your summary.
Alcohols can be oxidised using acidified Potassium Dichromate (IV). Primary alcohols will be oxidised to aldehydes and carboxylic acids so ethanol will make ethanal and ethanoic acid (see the reaction below).
To ensure this reaction happens, you will need to heat your ethanol with acidified potassium dichromate (IV). This is represented as [O] in the equation opposite. In order to get pure ethanal or ethanoic acid, once your reaction is complete, you will need to use a separation technique such as distillation.
4. Draw a labelled diagram showing how you would set up distillation equipment.
5. Explain how distillation separates two liquids mixed
Another separation technique you will have used before is paper chromatography. The diagram below shows thin layer chromatography, which is set up in the same way as paper chromatography except you use a silica plate rather than paper.
6. Write a short method explaining how to carry out paper chromatography
7. Describe how you would analyse your chromatogram to decide if you have a pure substance or not.
In organic chemistry we often heat volatile substances, so that they can be heated sufficiently to react without evaporating we use a technique called Reflux.
8. Find out what apparatus you would need to carry out reflex. Draw a labelled diagram and explain why it would be a good way to heat volatile compounds.
Group 1 Elements
Elements in the periodic table are arranged in groups. Elements in the same group have characteristic properties and exhibit trends in their reactivity. Group 1 elements of the periodic table are known as the alkali metals. You will have looked at the reactivity and trends in their behaviour at GCSE.
9. Describe the trend in reactivity of the group 1 metals with water and give balanced chemical equations for the reactions.
10. The graph opposite shows the size of the atomic radii of the group 1 elements. Describe the trend that you see and explain why we see this trend.
11. Studying the chemistry of elements is really useful and in 2019, three Chemists won the Nobel Prize for Lithium Ion batteries. Follow the link below to find out more about this group 1 metal application.
12. At A Level we start investigating group 2 metals. Using your knowledge of group 1, predict the following for group 2:
The trend in reactivity as you go down the group
The reaction with water, giving equations
The trend in atomic radii
Group 7 Elements
13. Group 7 elements are known as the halogens. They will also exhibit trends in their reactivity, compare the reactivity of the group 1 and 7 elements as you go down the group.
Taking the four elements in turn:
Produce a table that compares the state of each element at room temperature and then its colour in an aqueous solution.
14. When choosing to study Chemistry, the most important thing is that you have a real interest in the subject outside of the syllabus. How much do you know about the elements of the periodic table? Use the following links to find out more about individual elements e.g. how Chlorine was used in warfare and how it reacts with metals.