The Five Most Common Ways Students Lose Easy Marks in Science Exams
Some lost marks have very little to do with not knowing the science.
One of the most frustrating things I see when marking science work is a student who clearly understands the topic, has remembered the relevant facts, and may even have carried out the calculation correctly — yet still does not receive all the marks.
Sometimes the problem is surprisingly small.
The student forgets the unit.
They quote a calculator answer to eight decimal places when the question asks for three significant figures.
They describe a graph perfectly but never explain why the pattern occurs.
They make a sensible scientific statement but fail to use the data printed directly in front of them.
Or, perhaps most frustratingly of all, they answer the question they expected to see rather than the one that was actually asked.
These are not necessarily failures of scientific knowledge.
They are failures of exam technique.
And that distinction matters.
A student can spend another hour revising photosynthesis, electricity or forces and still continue losing the same marks unless someone identifies exactly how those marks are disappearing.
Over many years of teaching and tutoring, I have increasingly found that one of the most useful things we can do is stop asking only:
"Does the student know the science?"
and start asking:
"Can the student turn that knowledge into marks?"
Here are five of the most common ways students fail to do precisely that.
1. Forgetting the Unit
This must be one of the easiest marks to lose.
A student completes a calculation perfectly.
They substitute the correct values.
They rearrange the equation correctly.
Their calculator gives the right numerical answer.
And then they write:
12
rather than:
12 V
or:
12 N
or:
12 m/s
depending upon the question.
The science may be completely correct, but the answer is incomplete.
Why units matter
A number without a unit often has surprisingly little meaning.
Suppose I ask:
What is the speed of the object?
A student answers:
20
Twenty what?
20 metres?
20 seconds?
20 metres per second?
20 kilometres per hour?
The unit is part of the scientific information.
This is particularly important in physics, but it appears throughout science.
Students might encounter:
metres, m;
seconds, s;
metres per second, m/s;
newtons, N;
joules, J;
watts, W;
volts, V;
amperes, A;
ohms;
kilograms, kg;
grams, g;
cubic centimetres, cm3;
moles, mol;
grams per cubic decimetre, g/dm3.
A very simple example
Imagine a GCSE Physics question:
A car travels 150 m in 10 s.
Calculate its average speed.
The calculation is:
speed = distance / time
speed = 150 / 10
speed = 15 m/s
Writing simply 15 risks throwing away a mark that required virtually no additional scientific knowledge.
The habit I encourage
Before moving to the next question, look at the answer and ask:
"What is this number measuring?"
If you can answer that question, you can usually identify the unit.
Another useful habit is to write the unit beside the numerical value while carrying out the calculation rather than trying to remember it afterwards.
For example:
distance = 150 m
time = 10 s
speed = 150 m / 10 s
speed = 15 m/s
This makes forgetting the unit much less likely.
2. Ignoring Significant Figures or Decimal Places
Calculators are extraordinarily good at producing numbers.
Unfortunately, calculators do not know how many of those numbers you should write down.
Suppose a calculation gives:
4.736842105
That may be what appears on the screen.
It is rarely what belongs on the examination paper.
The question may specifically say:
Give your answer to 3 significant figures.
The correct answer would therefore be:
4.74
Writing 4.736842105 is not more scientifically impressive.
In fact, it may be incorrect.
Significant figures and decimal places are not the same
Students sometimes confuse the two.
Consider:
0.004763
To 2 significant figures:
0.0048
The first significant figure is the 4.
But to 2 decimal places:
0.00
These are very different instructions.
Another example:
12.746
To 2 decimal places:
12.75
To 2 significant figures:
13
Students need to recognise which instruction they have been given.
Why this matters scientifically
Precision communicates something about the reliability of a measurement.
If a ruler measures only to the nearest millimetre, reporting the result as:
12.347826 cm
would suggest a level of precision that simply was not present in the original measurement.
Examiners are therefore not being unnecessarily fussy when they ask for sensible rounding.
They are testing whether the student understands how scientific measurements are reported.
A useful examination rule
Unless the question gives another instruction, students should usually avoid rounding intermediate stages too aggressively.
Keep several figures in the calculator and round the final answer.
For example:
If:
energy = 4.673 x 2.18
do not unnecessarily round 4.673 to 4.7 before completing the calculation.
Use the accurate values first and round at the end.
3. Failing to Quote the Data
This is enormously common in biology, chemistry and physics.
A question provides a table or graph.
The student correctly identifies the trend.
They write:
"The rate increases as temperature increases."
Scientifically, that may be perfectly reasonable.
But the question might say:
"Use data from the graph to describe the relationship."
Now the examiner expects evidence.
A stronger answer might be:
"As the temperature increases from 20 degrees C to 40 degrees C, the reaction rate increases from 8 units to 21 units."
The student has now demonstrated that they actually used the information supplied.
The difference between an observation and evidence
Consider a biology investigation into enzyme activity.
A student writes:
"The enzyme works faster at higher temperatures."
That may earn something.
But:
"The reaction rate rises from 3.2 units at 20 degrees C to 7.8 units at 40 degrees C."
is much stronger.
The second answer supports the statement with evidence.
Look for instructions such as:
use data from the table;
use values from the graph;
give evidence from the results;
compare the results;
calculate the difference;
calculate the percentage change.
Whenever students see those phrases, numbers should immediately come to mind.
A particularly common comparison problem
Suppose one treatment produces:
84 seedlings
and another:
56 seedlings.
Writing:
"More seedlings grew in treatment A."
is true.
But the examiner may expect something such as:
"Treatment A produced 84 seedlings compared with 56 in treatment B, an increase of 28 seedlings."
Depending upon the question, the student might even calculate:
percentage increase = increase / original value x 100
percentage increase = 28 / 56 x 100
percentage increase = 50%
Now the comparison is much more precise.
My advice to students
If the question gives you numbers, there is often a reason.
Use them.
4. Confusing "Describe" with "Explain"
This is one of the biggest exam-technique problems in science.
The two words may sound similar in everyday conversation.
In an examination, they usually require very different answers.
Describe means: What happens?
Suppose a graph shows the rate of photosynthesis as light intensity increases.
A description might say:
"The rate of photosynthesis increases rapidly at first and then levels off."
That tells us what the graph shows.
Explain means: Why does it happen?
An explanation might say:
"At low light intensity, light is the limiting factor, so increasing light intensity increases the rate of photosynthesis. At higher light intensities another factor, such as carbon dioxide concentration or temperature, becomes limiting, so the rate levels off."
Now we have explained the mechanism.
Another example: resistance and temperature
Question:
Describe what happens to the resistance of a filament lamp as the current increases.
Possible answer:
"The resistance increases."
Question:
Explain why the resistance increases.
Now we need something more like:
"As the current increases, the filament becomes hotter. The metal ions vibrate more strongly, causing more collisions with the moving electrons, so the resistance increases."
The second question requires physics.
The first does not necessarily require the mechanism at all.
Command words are instructions
Students often treat command words as decoration.
They are not.
Words such as:
state;
give;
identify;
describe;
compare;
explain;
calculate;
determine;
evaluate;
suggest;
tell the student what sort of answer is required.
One of the most useful exam habits is therefore remarkably simple:
Underline the command word.
Before answering, decide what it is asking you to do.
5. Giving a Correct Scientific Answer That Does Not Answer the Question
This is perhaps the most important of all.
A student sees a familiar topic.
They recognise a keyword.
Their memory activates.
And they start writing everything they know.
Unfortunately, the examiner did not ask for everything they know.
An example from biology
Imagine the question asks:
"Explain why vaccination can reduce the spread of a communicable disease through a population."
A student writes:
"Vaccines contain antigens from a pathogen. These stimulate lymphocytes to produce antibodies and memory cells."
That is good biology.
But has the student fully answered the question about reducing spread through a population?
Not yet.
They need to connect individual immunity to transmission.
A stronger answer might continue:
"If a large proportion of the population is immune, infected individuals are less likely to encounter susceptible people. This reduces transmission and can provide some protection to people who are not immune."
Now the answer addresses the actual question.
An example from chemistry
Question:
"Explain why increasing the concentration of hydrochloric acid increases the rate of reaction with magnesium."
Student answer:
"Particles move randomly."
True.
But insufficient.
A better answer:
"Increasing the concentration means there are more acid particles per unit volume. This produces more frequent successful collisions with the magnesium surface, so the reaction rate increases."
Again, the student needs to make the complete logical connection.
An example from physics
Question:
"Explain why using a higher potential difference increases the current through a fixed resistor."
A student might write:
"Current is measured in amperes."
Scientifically correct.
Completely irrelevant.
Knowing science is not enough.
You have to select the science that answers the question.
The Dangerous Habit of Keyword Answering
This is something I frequently try to identify during tuition.
A student sees:
"photosynthesis"
and immediately writes something about chlorophyll.
They see:
"electricity"
and write V = IR.
They see:
"enzymes"
and write about active sites.
All of those things might be correct.
But examination questions are increasingly designed to test whether students can apply ideas rather than simply reproduce memorised paragraphs.
The better habit is:
Read the whole question.
Identify the command word.
Identify the scientific topic.
Identify the specific context.
Look at the number of marks available.
Build the answer around what has actually been asked.
That short pause can save a remarkable number of marks.
Use the Number of Marks as a Clue
The mark allocation is useful information.
If a question is worth one mark, the examiner probably does not want a page of writing.
If it is worth four marks, a one-sentence answer is unlikely to be enough.
Consider:
Explain how insulation reduces energy transfer from a house. [4 marks]
A student writing simply:
"Insulation keeps the house warm."
has probably not done enough.
They might need to discuss particular mechanisms:
reducing conduction through walls;
trapping air;
reducing convection;
reflective surfaces reducing infrared radiation.
The number of marks gives a rough indication of how much scientific content is expected.
It does not always correspond to exactly one sentence per mark, but it is an extremely useful warning system.
A Practical Checking Routine Before Moving On
I encourage students to develop a quick final check.
It does not need to take long.
Ask:
1. Did I answer the command word?
If it says explain, have I given a reason?
If it says describe, have I stated the pattern?
2. If there was data, did I use it?
Have I quoted appropriate values?
3. If I calculated something, did I include the unit?
4. Did the question specify significant figures or decimal places?
5. Have I answered this question rather than simply written something I know about the topic?
That entire check can sometimes take only a few seconds.
Yet across a complete GCSE or A Level paper, those few seconds can protect a surprisingly large number of marks.
The Importance of Showing Working
There is another reason I encourage students not simply to type everything into a calculator and write down the final number.
Examiners can often award method marks.
Suppose the correct calculation is:
power = energy / time
A student writes:
power = 18,000 / 120
power = 150 W
If the final arithmetic goes wrong but the method is correct, some marks may still be available.
Compare that with a student who writes only:
137 W
with no working.
The examiner has very little evidence of what the student attempted.
Showing working is therefore not simply for the teacher.
It can protect marks.
Why Practice Papers Alone Are Not Always Enough
Students are often told:
"Do more past papers."
That can certainly help.
But there is an important limitation.
If a student repeatedly makes the same exam-technique mistake, simply completing more papers can mean practising that mistake again and again.
A student who habitually forgets units might complete six papers and forget units six times.
A student who never quotes data may continue writing vague descriptions.
A student who misinterprets "explain" may continue producing descriptive answers.
The important stage is not simply doing the paper.
It is analysing why marks were lost.
When I go through a paper with a student, I am interested not only in the total mark but in the pattern.
Was the science unknown?
Was the equation forgotten?
Was the question misread?
Was the unit missing?
Was the response too vague?
Was evidence missing?
Was the student answering from memory instead of reading the question?
Those are very different problems and require very different solutions.
Create a "Lost Marks" List
One practical technique I particularly like is keeping a short record of avoidable mistakes.
For example:
My Lost Marks List
Forgot units.
Rounded too early.
Did not quote graph values.
Described instead of explained.
Did not read the final sentence of the question.
Forgot to show working.
Used vague wording such as "it" and "things".
Did not compare both sets of data.
The list should be personal.
After several papers, patterns usually begin to appear.
Perhaps the student discovers that they have lost nine marks across three papers simply because of missing units.
That is valuable information.
Fixing that habit is potentially much easier than learning an entirely new topic.
Parents Can Help Without Teaching the Science
This is also an area where parents can sometimes provide useful support even if they have not studied science for decades.
You do not necessarily need to know whether the scientific explanation is correct.
You can still ask:
"What exactly is the question asking you to do?"
"Where have you used the figures from the graph?"
"What unit should that answer have?"
"The question says explain. Where is the reason?"
"It is worth three marks. Have you given enough information?"
Those questions encourage examination discipline without requiring the parent to become a physics, chemistry or biology teacher.
Knowledge and Examination Skill Are Different Things
There is an important lesson here.
Science examinations do not simply test what students know.
They also test whether students can:
interpret information;
select relevant knowledge;
communicate precisely;
work with data;
perform calculations;
follow instructions;
construct explanations;
apply ideas to unfamiliar situations.
That is why a student can walk out of an examination saying:
"I knew all of that!"
and still be disappointed by the result.
They may genuinely have known it.
But marks are awarded for what appears on the examination paper, not for what was present somewhere inside the student's head.
Conclusion: Sometimes the Fastest Improvement Is Not More Revision
Revision matters enormously.
Students need secure scientific knowledge.
They need to understand equations, processes, practical methods and key terminology.
But there comes a point where simply learning more facts produces diminishing returns.
Sometimes the quickest improvement comes from protecting the marks that the student was already capable of earning.
Remember the unit.
Round properly.
Quote the data.
Respect the command word.
Answer the question that is actually on the page.
None of these techniques is particularly glamorous.
They will not replace proper scientific understanding.
But over the course of a full examination paper they can make a substantial difference.
And perhaps that is one of the most useful lessons we can teach students about examinations:
You do not always need to know more science to gain more science marks. Sometimes you simply need to show the examiner more clearly what you already know.
No comments:
Post a Comment