WELCOME TO CHEMISTRY
INTRODUCTION
Name
: Mr. Gwishiri
Contact
: 0774 364 029
Course Code
: 6031
Sections
: 4 sections
Topics to be covered : 24 topics
Period
: 4 terms
ZIMSEC final examination consists of four papers
Paper
Sections &
number of
questions
1
Number of questions to be
answered / Type of paper
Questions are from the
following / Duration
Paper
total
marks
Weighing
A&B / 30:10 total Answer all / multiple
40
choice
Core syllabus / 1hr
40
16
2
6
Answer all / structured
Core syllabus / 1hr 30mins
60
24
3
A,B,C&D /
3:2:3:2 total 10
2-A, 1-B, 2-C & 1-D total 6/
free response
Core syllabus / 2hrs 30mins
90
40
4
3
Answer all / practical
Quantitative, qualitative
analysis & design / 2hrs 30mins
50
20
Expectations
 ATTEND ALL THE LESSONS.
 To have 3 counter books 1 for notes, 1 for tests and 1 for practicals. Would rather
prefer it if you have them with large number of pages especially Notes. This is to your
advantage during revision.
 To have 2 exercise books 1 for exercises and the other for home work.
 Revisit the topics covered during the day/week/month/term and year.
 To work together as a group, the person next to you is now your brother/sister ‘You
don’t leave a brother/sister behind’.
 To work extra hard, because chemistry as well as A level requires your whole
attention.
 The above expectations will distinguish between an A and an O student.
CHEMISTRY TERMINOLOGY AND
MEANINGS
1 Define … means give the precise meaning of a word, phrase, or physical quantity.
Example: Define the term isotopes. [1]
Answer: Isotopes are atoms of the same element, with different numbers of
neutrons
2 What do you understand by/What is meant by … is similar to Define.
Example: What do you understand by the term cracking? [2]
Answer: Cracking is the process in which molecules with long carbon chains are broken into
more useful molecules with shorter chains. It always gives at least one product with a
carbon-carbon double bond.
3 State … means give a specific name, value, or other brief answer without explanation
or calculation. State and Name are very similar instructions.
Example: State the chemical name for quicklime. [1]
Answer: Calcium oxide
4 List … means give a sequence of names or other brief answers with no explanation. If
the question asks for three points, give only three.
Example: List three physical properties that metals tend to share. [3]
Answer: Good conductors of electricity; malleable; high melting points.
5 Explain … means give a detailed account of causes, reasons, or mechanisms.
Example: Explain why chlorine is added to water at water treatment works. [1]
Answer: It kills bacteria, so it makes the water safer to drink.
6 Describe … means give a detailed account. If you are asked to describe a process,
you could set the steps out as numbered points. You could include a diagram if that is
appropriate.
Example: Desribe how dry crystals of copper(II) sulfate could be obtained from an
aqueous solution of copper(II) sulfate. [4]
Answer: The crystals could be obtained by these steps:
 1 Heat the solution to evaporate some of the water.
 2 Leave the solution to cool. Crystals form.
 3 Filter off the crystals and pour a little distilled water over them in the funnel, to rinse
them...
 4 Use filter paper to pat the crystals dry.
7 Describe and explain … means give a detailed account, including causes, reasons, or
mechanisms.
Example: Describe and explain the colour change, when orange bromine water is
shaken with ethene gas. [2]
Answer: The orange colour disappears. This is because the bromine molecules add on to
the ethene molecules at the double bond, giving the colourless liquid 1,2dibromoethane.
(Note: you could also explain here by drawing out the structural formulae.)
8 Outline … means give a brief account or summary.
Example: Barium sulfate is an insoluble salt. Outline the preparation of pure, dry barium
sulfate, starting from solid barium chloride. [4]
Answer: These are the steps:
 1 Prepare a solution of barium chloride.
 2 Add a solution of a soluble sulfate, such as magnesium sulfate. A precipitate of
barium sulfate forms.
 3 Filter off the precipitate, and rinse it in the filter paper, using distilled water.
 4 Dry it in a warm oven.
9 Predict … means suggest an answer, based on other pieces of information. If your
answer is a number, you could write roughly, or about before the number.
Example: The element caesium is two places below potassium in Group I of the Periodic
Table. Using what you know about potassium, predict one physical and one chemical
property of caesium. [2]
Answer: Physical property: very soft metal. Chemical property: reacts explosively with
water, giving an alkaline solution of caesium hydroxide.
10 Deduce … means to reach a conclusion from the information given. You should
include a sentence to support your answer where you explain your reasoning, or refer to
a principle or law that you have learnt.
Example: The formulae for the first three members of the alkene family are: C2H4 C3H6
C4H8. Deduce the formulae for the next two members. [2]
Answer: C5H10 and C6H12
(general formula for alkenes is CnH2n)
11 Suggest … means propose a hypothesis or other possible answer. You may have to
use your general knowledge and apply it to a new situation.
Example: Suggest a suitable method for obtaining sodium from sodium chloride.
Answer: Electrolysis of the molten compound will give sodium at the cathode.
12 Calculate … find a numerical answer, showing the relevant stages in your working
(unless you are instructed not to do so). The question will provide the data you need to
complete the calculation.
Example: Calculate the relative formula mass for ammonium nitrate, NH4NO3. The Ar
values are: N = 14, H = 1, O = 16.
Answer: 80
13 Find … means ‘work out’. You usually have to do a calculation.
Example: Find the % of silicon by mass, in silicon dioxide, SiO2. The Ar values are: Si = 28, O
= 16. [1]
Answer: 46.7%
(Mr for SiO2 pt = 28 + 2 x 16 = 60; the % which is silicon = 28/60 × 100 = 46.7%)
14 Determine … It usually means you have to do a calculation, by substituting known
values into a formula.
Example: 6 g of carbon reacts completely with 16 g of oxygen to give 22 g of carbon
dioxide. Determine the masses of carbon and oxygen needed to give 55 g of carbon
dioxide.
Answer: 15 g of carbon and 48 g of oxygen
(55/22 × 6 = 15, 55/22 × 16 = 40)
15 Estimate … find an approximate value for an unknown quantity. You may need to do
a calculation. You should use the term about, approximately, or roughly, in your answer.
Example The carboxylic acids form a homologous series. This table gives data for four of
them.
acid
formula boiling point /°C
methanoic HCOOH
101
ethanoic
CH3COOH 118
butanoic
C3H7COOH
164
pentanoic C4H9COOH
187
16 Sketch … means draw freehand. Your sketch can be quite rough, but make sure you
show the key points correctly.
Example: Excess hydrochloric acid is added to small lumps of calcium carbonate in a
flask. Carbon dioxide bubbles off. The flask is weighed at intervals. Curve X below shows
the results. On the same axes, sketch the curves obtained if the experiment is repeated:
a) a more concentrated solution of acid. label this curve y.
b) larger lumps of calcium carbonate, of the same mass. Label this curve Z. [2]
Answer:
Note that:
- the curves all start at zero
- the final loss of mass is the same each time
- each curve gets less steep as the reaction
proceeds
- Y has the steepest slope, and Z the least steep,
overall.
17 Discuss means give a critical account of the points involved in the topic.
Example: Discuss the importance of adding a catalyst to a reaction.
Answer: A catalyst speeds up the rate of a reaction which means it saves time, it is
also retrieved after the reaction and that means it can be reused several times thus a
catalyst is economical.
18 Comment is intended as an open-ended instruction, inviting candidates to recall
or infer points of interest relevant to the context of the question, taking account of
the number of marks available
Example: Comment on the reactivity of phenol and nitrobenzene. [1]
Answer: Phenol is more reactive than nitrobenzene because OH is an activating
group and NO2 is deactivating.
19 Construct is often used in relation to chemical equations where a candidate is
expected to write a balanced equation, not factual recall but by analogy or by using
information in the question.
Example: Ethanol can be oxidized to ethanoic acid by several oxidizing agents. Construct
a half equation for the oxidation of ethanol. [2]
Answer:
CH3CH2OH + H2O → CH3COOH + 4H+ +4e20 Compare requires candidates to provide both the similarities and differences between
things or concepts.
Example: Compare the basicity of phenylamine and 1 butyl amine.
Answer: 1butyl amine is more basic because the alkyl group (butyl) has positive inductive
effect which makes the lone pair of electrons more available for dative bonding hence its
more basic.
21 Classify requires candidates to group things based on common
characteristics.
Example: Classify the following organic compounds; 2 methyl butan2ol and
ethanol
Answer: 2 methyl butan2ol – tertiary alcohol and ethanol – primary alcohol