C1.31a Different models You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. The diagrams show some different ways of representing molecules such as propane.
Propane
1
Which model is the easiest to use to: a
work out how many hydrogen atoms there are in a molecule of propane
b
see how the atoms are joined together
c
see the shape of the molecule?
Methylcyclohexane The same kinds of diagram can be used to represent more complicated molecules. These diagrams show methylcyclohexane (formula C7H14).
2
Look at the models for methylcyclohexane. What does the structural formula tell you that the molecular formula does not?
3
Which model is the easiest to use to work out how all the different atoms are arranged in a methylcyclohexane molecule? Explain your answer.
4
What are the advantages and disadvantages of:
5
a
a formula compared to a ball-and-stick model
b
ball-and-stick model compared to a structural formula?
What are the advantages and disadvantages of a ball-and-stick model compared to a physical model such as one you might make in a lesson?
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
C1.31b Naming conventions You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. In everyday life we refer to sodium chloride as 'salt' when we add it to food. However, to a chemist the word 'salt' means a particular type of compound and could refer to one of many different substances. In addition, the same substance can have different everyday names in different countries. There were similar problems when scientists in different countries first started to make lots of discoveries about chemistry and wrote about their discoveries. The first recommendations for a worldwide system of naming compounds were made by a French chemist, Louis-Bernard de Morveau (1737–1816) in 1782. Other scientists developed his ideas and published them in books in their own countries. However, it wasn't until 1892 that an international conference was held to agree to a system of naming compounds. This was even more important by now because many more compounds had been made or discovered. The present system of naming is organised by the International Union of Pure and Applied Chemistry (IUPAC). They hold international conferences to agree on the names for new compounds or groups of compounds. It publishes several books with the standard names for compounds. The Blue Book includes the naming system for hydrocarbon compounds. 1
a
Why is it important that scientists in different countries always use the same name for the same substance?
b
Why is this even more important today than it was in 1782?
2
Why do you think the IUPAC holds conferences to agree new names?
The cards below show the structures of different forms of hexene. They only show the ‘carbon skeleton’ of each of the molecules.
A
H C
C H
H H C
B H
C H
D
H
H
H
C
C
C
C
H
H
H
H
C
H H
H C
C
H
H
H
H
H
H
H
H
C
C
C
C
H
H H
H H
H
C
H C H
C
C
H
C
H
H
H
H H C
C
C
C
C
H
H
H
H
© Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
H H C
H
C
C
C
H
H
H
HC
C
H
H
G
H
C
H C
C
H
H
C
H
H
H
H H
H
C
C
H
H
H
H H
H
H C
C H
C
H
H
C C
H H H
I
H
C H H
F
H
C
H
E
H
C
H H
H H
H
H H
C
C
H
H
H
H
C
H
H H
H H
H
H
C
C
H
C H
C
C
C
H H
H
H
H C
J
H C
H
H
C H
H
C
H H
HH C
H
C
C
H
H
H
H
C1.31c Alkanes and alkenes Name
Class
Date
The drawings show a molecule of ethene and a molecule of ethane. 1
2
How many carbon atoms are there in a molecule of: a
methane
b
ethane
c
propane?
What is the difference between ethane and ethene? __________________________________________________________________________________
3
4
a
Draw the structure of a molecule of methane in the box.
b
Write the formula for a molecule of methane.
a
Draw the structures of molecules of propane and propene.
propane
5
b
Write the formula for propane.
c
Write the formula for propene.
propene
What would happen if you shook up bromine water with the following gases: a
propane
b
propene?
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
methane
C1.31d Alkane and alkene questions Name
Class
Date
The drawings show a molecule of ethane and a molecule of ethene.
A
B
1
Which molecule is ethane? Explain how you worked out your answer.
2
a
What would you see if you shook up ethane with some bromine water?
b
What would you see if you repeated the test with ethene?
c
Explain your answers.
a
Write down the formulae for propane and propene.
b
Draw the structures of molecules of propane and propene.
3
propane
propene
H4 Write balanced equations for the complete combustion of: a
propane
b
propene
Extra challenge 5
‘pent-’ means five. Draw the structure of a molecule of pentane.
© Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.