Why Laboratory Work Matters — Even When the Examination Is Written
You can memorise an experiment from a textbook. You understand it rather differently after you have actually done it.
One of the slightly strange things about science education is that, for many students, the final examination is largely a written one.
They sit at a desk. They answer questions. They draw graphs. They identify variables. They comment on uncertainty. They suggest improvements to experiments.
Yet all of those questions are supposedly about practical science.
That raises an obvious question.
If the examination is written, how important is it actually to do the experiments?
My answer is: very important indeed.
There is an enormous difference between reading that a burette should be read at eye level and actually standing in front of one, trying to decide whether the bottom of the meniscus is at 23.40 cm3 or 23.45 cm3.
There is a difference between memorising a circuit diagram and connecting the components yourself — only to discover that nothing happens because the ammeter is in the wrong place or one connection is loose.
And there is a considerable difference between being shown a perfect straight-line graph in a textbook and collecting your own data to discover that one of your points appears determined to be somewhere completely different from all the others.
That is where practical science becomes valuable.
It turns science from something that students are told into something they can investigate.
Science Is Supposed to Be Experimental
Science is not simply a collection of facts.
It is a method of finding things out.
At its heart are questions such as:
What do I think will happen?
What should I change?
What should I measure?
What must I keep constant?
How accurately can I measure it?
Are my results reliable?
Does my evidence support my conclusion?
What could I do better next time?
Those are precisely the questions students encounter in GCSE and A-level examinations.
But they make much more sense when the student has actually had to answer them during an experiment.
The phrase "control variable", for example, can become another definition to memorise.
Carry out an experiment and it suddenly has a purpose.
If we are investigating how light intensity affects photosynthesis, then perhaps temperature needs to remain approximately constant.
Why?
Because if the temperature changes as well as the light intensity, how do we know which variable caused any change we observe?
That is experimental thinking.
And it is much easier to understand when the problem is real.
Textbook Experiments Are Suspiciously Well Behaved
One of the lessons students quickly learn in a laboratory is that real experimental results are rarely as neat as the examples in textbooks.
Textbook graphs often contain beautifully positioned points.
Real graphs do not.
Perhaps a ruler was read slightly incorrectly.
Perhaps the temperature changed.
Perhaps there was a small parallax error.
Perhaps the equipment moved.
Perhaps the reaction had not quite finished.
Perhaps a component heated up during the experiment.
Or perhaps there is a genuinely anomalous result that needs investigating.
This is enormously useful.
Students begin to understand that experimental science is not about obtaining the answer that the textbook says you should obtain.
It is about obtaining evidence and then deciding how much confidence you should place in it.
That distinction becomes increasingly important at A-level.
Titration: Reading About the End Point Is Not the Same as Finding It
Titration is a wonderful example.
On paper, it sounds straightforward.
Fill a burette.
Measure a solution into a conical flask.
Add an indicator.
Run one solution into another until the indicator changes colour.
Record the titre.
Repeat until concordant results are obtained.
Easy.
Until you actually do it.
The first attempt may rush straight past the end point.
The student discovers that the tap on a burette requires more control than expected.
Then comes another attempt.
This time, close to the end point, the solution is added drop by drop.
Eventually there is that moment when one final drop changes the colour.
The student has now experienced what "end point" actually means.
They also understand why a rough titration is useful, why repeated measurements matter and why concordant titres provide greater confidence in the result.
When an examination later asks:
"Why should the titration be repeated?"
the answer is no longer an isolated fact.
It is connected to an experience.
Electricity: A Circuit Diagram Is Only the Beginning
Electrical circuits provide another excellent example.
A student can learn perfectly well that an ammeter should be connected in series and a voltmeter in parallel.
They may even reproduce the correct circuit diagram.
But give them an actual power supply, resistor, ammeter, voltmeter and a collection of leads and another level of understanding appears.
Where does this wire go?
Why is the reading zero?
Why has the current suddenly changed?
Why shouldn't I connect the ammeter directly across the power supply?
What happens if the resistance changes?
Students discover that a circuit diagram is not simply a drawing.
It represents a physical system.
This is particularly important when moving on to experiments involving current-voltage characteristics, resistance, series and parallel circuits or resistivity.
A student who has built circuits tends to interpret circuit questions rather differently from one who has only seen them on paper.
Young's Modulus: When Measurement Becomes the Experiment
Young's modulus is another good example because it forces students to confront measurement.
The principle can appear beautifully simple in a textbook.
Apply a force to a wire.
Measure its extension.
Calculate stress and strain.
Determine Young's modulus.
But the actual experiment immediately raises questions.
How accurately do we know the original length of the wire?
How accurately can we measure its diameter?
If we use a micrometer, should we measure the diameter at several points?
Why?
How small is the extension?
Could the wire have been slightly bent before the experiment started?
How do we ensure that the deformation remains elastic?
Suddenly, uncertainty is no longer an abstract chapter in the specification.
It matters because the quality of the final answer depends upon the quality of the measurements.
Microscopy: Seeing Something Changes Understanding
Biology benefits enormously from practical work for a slightly different reason.
A diagram of a plant cell is useful.
Looking at actual plant cells through a microscope is better.
The student discovers immediately that real cells do not have conveniently thick black outlines and enormous labels pointing towards their components.
They have to:
prepare a specimen;
position it correctly;
adjust the illumination;
focus the microscope;
select an appropriate magnification;
identify structures;
perhaps produce a biological drawing.
Even focusing the microscope teaches something.
A student begins to appreciate depth, scale and the limitations of an optical instrument.
And when magnification calculations appear in an examination, they are connected to something physical rather than being merely another equation.
Photosynthesis: A Simple Experiment That Raises Complicated Questions
Photosynthesis provides several possibilities for practical investigation.
One familiar experiment uses an aquatic plant and changes the light intensity.
The apparently simple question is:
Does increasing light intensity increase the rate of photosynthesis?
But carrying out the investigation soon produces more questions.
How are we going to measure the rate?
Count bubbles?
Measure the volume of oxygen?
How far should the lamp be from the plant?
Should we allow the plant time to adjust before taking a reading?
Could the lamp warm the water?
Would temperature then become another variable?
What happens when increasing the light intensity stops producing much increase in photosynthesis?
Now the student is beginning to think about limiting factors, experimental design and the quality of evidence.
That is much richer than simply memorising a diagram showing a lamp next to a piece of pondweed.
Waves Become Much Easier When You Can See Them
Waves are notoriously difficult because students are often asked to imagine something dynamic from static diagrams.
Practical work changes this.
A ripple tank can show reflection and diffraction.
A string can demonstrate stationary waves.
A signal generator and oscilloscope can make frequency and amplitude visible.
Resonance can be demonstrated instead of merely defined.
With appropriate sensors and video, some experiments can be slowed down, measured or analysed afterwards.
Students begin to connect the diagram in the textbook with an actual physical process.
That connection is extremely powerful.
Mechanics: Things Do Not Move Like Examination Diagrams
Mechanics becomes particularly interesting experimentally.
A textbook may show a neat object moving down a slope.
In reality there is friction.
The surface may not be perfectly level.
Timing measurements have uncertainty.
Sensors need positioning.
An object may wobble.
A trolley may not start from exactly the same point each time.
Modern data-logging equipment can make this especially useful because students can collect position, velocity, acceleration or force data and examine the resulting graphs.
Then a velocity-time graph is no longer just something appearing in an examination question.
It represents the motion of something the student has actually watched.
Practical Work Teaches Students to Ask: "Is That Result Sensible?"
This may be one of the most valuable scientific skills of all.
Students sometimes become so focused on calculations that they forget to look at the answer.
Suppose an experiment produces a result that is ten times larger than expected.
Is the theory wrong?
Possibly.
But before rewriting physics, chemistry or biology, we should probably check the experiment.
Was a unit converted incorrectly?
Was the apparatus read correctly?
Was one measurement entered incorrectly?
Was there an anomalous result?
Was the equipment zeroed?
Was the scale appropriate?
Practical experience encourages students to develop a scientific instinct.
Does this answer make sense?
That is valuable both in the laboratory and in the examination room.
Watching an Experiment Is Useful — But It Isn't Quite the Same
There are now excellent science videos available online.
I use video myself because it can be extremely useful.
A camera can show a close-up that would otherwise be difficult to see.
Slow motion can reveal something happening too quickly for the eye.
Thermal imaging can show temperature differences.
Data captured electronically can be displayed immediately.
Video can also demonstrate experiments that would be impractical, expensive or unsafe for an individual student to carry out.
But watching somebody else do an experiment is still not quite the same as doing it yourself.
When watching a video, everything normally works.
The apparatus has already been chosen.
The equipment is already assembled.
The camera points towards the important part.
The presenter knows what is going to happen.
The student becomes an observer.
When carrying out the experiment, the student becomes responsible.
They have to make decisions.
And occasionally things go wrong.
That is not a failure of practical science.
Sometimes it is the most educational part.
The Experiment That Doesn't Work Can Be the Best Experiment
If an experiment produces unexpected results, I rarely see that automatically as a disaster.
Instead I can ask:
Why?
Perhaps the circuit has been assembled incorrectly.
Perhaps one variable was not controlled.
Perhaps the measurements were not sufficiently precise.
Perhaps the apparatus itself is unsuitable.
Finding the problem can require more thought than following a perfect set of instructions.
This is one reason I value practical science within tuition.
I do not simply want students to remember the expected result.
I want them to understand how we know.
Practical Science and Examination Technique Are Closely Connected
It is easy to think of practical work and examination preparation as competing for lesson time.
I see them as complementary.
Consider the types of questions students regularly meet:
Identify the independent variable.
State the dependent variable.
Give two control variables.
Explain why the experiment should be repeated.
Identify an anomalous result.
Suggest an improvement to the method.
Explain why a particular instrument is appropriate.
Calculate percentage uncertainty.
Plot a graph.
Draw a line of best fit.
Determine a gradient.
Explain whether the evidence supports the hypothesis.
Every one of those skills becomes more meaningful when students have actually performed experiments.
If you have never struggled to take a measurement, "improve the precision of the measurement" can sound like examination jargon.
Once you have struggled with the measurement yourself, it becomes obvious what the question is really asking.
Going Beyond the Minimum Practical
There is another advantage.
Once a student becomes comfortable with practical science, we can go beyond merely reproducing the specification.
We can ask:
What happens if we change something?
Could we measure this another way?
Could a sensor collect better data?
Could we film the experiment in slow motion?
Could we use thermal imaging?
Could we plot the results electronically?
Could we design our own investigation?
This moves the student from following a recipe towards genuine scientific thinking.
It can also rekindle interest in a subject that has sometimes become dominated by revision guides and examination questions.
Science Should Occasionally Produce a "Wow"
Not every experiment has to be spectacular.
A careful titration can teach far more chemistry than an explosion.
But science should occasionally surprise us.
Seeing cells through a microscope for the first time can do that.
Watching a stationary wave form can do that.
Seeing a Van de Graaff generator produce a discharge can do that.
Watching data appear live from a moving trolley can do that.
Observing temperature patterns through a thermal camera can do that.
The important part is what comes afterwards.
Why did that happen?
That question turns spectacle into science.
Practical Work Builds Confidence
There is also something less easily measured.
Students who perform practical work often become more confident talking about science.
They have something concrete to refer to.
Instead of saying:
"I think the book says..."
they can say:
"When we did the experiment..."
That small change matters.
Science begins to belong to them.
They are no longer simply repeating somebody else's observations.
They have made observations of their own.
The Written Examination Tests More Than Writing
Ultimately, a written science examination is attempting to test whether a student understands how science works.
The paper may be made of questions, diagrams, graphs and calculations.
But behind many of those questions is a laboratory.
There is apparatus.
There are measurements.
There are variables that need controlling.
There are readings that contain uncertainty.
There are anomalous results.
There are conclusions that need defending with evidence.
A student who has actually experienced those things has a considerable advantage.
Not because practical work provides a collection of answers to memorise.
But because it provides a framework for understanding the questions.
From Memorising Science to Understanding It
A student can certainly memorise the method for a titration.
They can memorise where the ammeter goes.
They can memorise the equation for Young's modulus.
They can memorise how to calculate magnification.
They can memorise what a line of best fit should look like.
But science becomes something rather different when they have stood beside the equipment and attempted to make it work.
They discover that measurements are imperfect.
They discover that apparatus has limitations.
They discover that results have to be interpreted.
They discover that mistakes can teach you something.
Most importantly, they discover that science is not simply a body of knowledge handed down in a textbook.
It is a way of investigating the world.
And that is why, even when the examination is written, laboratory work still matters.
