How to Tackle Misconceptions in GCSE Physics

In my time teaching GCSE physics, I have come across an alarming number of misconceptions. I’ve heard everything, from widely held beliefs, such as ‘there’s no gravity in space’ to adamant assertions, such as ‘that skydiver definitely moved up when he opened his parachute’. 

I don’t blame students for having these ideas; after all, physics can sometimes seem counterintuitive, and the laws of physics are constantly being misused and distorted for entertainment in TV and film. However, when your GCSE exams are on the horizon, you need to be ready to challenge any misconceptions you might have and develop strategies for overcoming them. 

What is a misconception and where do they come from?

Misconceptions are ideas people form about the world, usually when they are very young, which are incorrect, or incomplete. 

They can originate from numerous sources; for example, parents may pass on common myths, such as ‘you mustn’t go swimming for an hour after eating’, and everyone has heard a semi-plausible rumour going around the playground at some point, such as ‘if you swallow bubblegum it will stay in your stomach for seven years’. 

The more you hear people repeating these ideas, the more you tend to believe them. However, as the Russian writer Tolstoy once said:

'A misconception remains a misconception even when it is shared by the majority of people.'

Shared misconceptions are especially difficult to tackle. Many of the ideas and concepts that you will come across in physics are common to everyday life, and many words that are used in physics are used in several different contexts which can add to the confusion.

What are the top misconceptions in physics?

Top three misconceptions about forces and motion

1. A constant force is needed to keep an object moving

At a young age, we learn that force causes motion. The issue with this fact is that students may then begin to think that a moving object must have a force acting on it in order to keep moving.

Newton's first law of motion tells us that 'an object will remain at rest or move with constant velocity unless acted on by a resultant force'.

This means that a force is needed to change the motion of an object, but it is not needed to keep it in motion. 

If you were to slide a book across a table, it would move for a time before coming to a stop.

• There is an initial force which sets the book into motion.

• When your hand is no longer in contact with the book, the force does not continue to act on it.

• The book then comes to a stop, but not because of the absence of a force, but because of the presence of another force, i.e. friction between the table and the book.

• In the absence of friction, the book would continue to move across the table with the same speed and direction.

2. Heavier objects sink in water while lighter ones float

The problem with this statement is that it is true in some cases, but not always. As a result, students can fall into the trap of thinking it must always be correct. 

Students can then find it difficult to understand why, for example, a large cruise ship floats while a small metal screw sinks.

The reason objects sink and float is due to the density of the object, rather than its mass.

• Density describes the distribution of the mass of an object over its volume.

• If an object has a lower density than water, it will float; if it has a greater density than water, it will sink.

• This means that heavy objects can float if their mass is spread out over a large volume and light objects can sink if their mass is contained in a small volume.

3. Skydivers move up when they open their parachute

When learning about terminal velocity, students often watch videos of skydivers jumping out of planes. At the point when the skydiver opens their parachute, they appear to move up.

In reality, the skydiver is slowing down, or falling, at a slower rate.

• This means there is an acceleration in the opposite direction to the skydiver’s motion.

• This upward acceleration is caused by air resistance.

• In order for the skydiver to move upwards, they would have to come to a complete stop first.

Top three misconceptions about electricity

1. Electricity, or electrical charges, are stored in the battery

This is an extremely common misconception among students. It comes from the idea that batteries are required to power electrical devices, and that, therefore, the battery must somehow ‘contain electricity’. It may also be reinforced by the idea that some devices, such as phones, require charging by plugging them in to ‘restore’ the depleted levels of ‘electricity’ in the battery.

It is important to understand that the term ‘electricity’ does not have an exact meaning, as it is a concept or a phenomenon rather than a physical quantity.

• A singular ‘battery’ is a call, and in physics a collection of cells is called a battery

• A cell is a store of energy.

• Electrons are charged particles which exist in all atoms.

• The delocalised electrons in the wires of the circuit make up the current that flows. There is no ‘store’ of charge, or electrons, in the cell.

• When a cell or battery is connected to a circuit, the chemicals in the cell supply energy to the charges (electrons).

• When the circuit is switched on, the charges (electrons) located in the wires begin to move.

2. Current flows out of both terminals of the battery and into the lightbulb

A surprising number of students believe a lightbulb only requires one wire connected to a battery to work, and that the second wire only supplies the lightbulb with more current. 

Direct current (the type of current produced from a cell) flows in one direction only, and for it to flow, the circuit must form a complete loop.

• Cells have positive (+) and negative (–) terminals.

• This sets up the difference in electrical potential, i.e. the potential difference, or voltage.

• Electrons are negatively charged; therefore, they must flow away from the negative terminal of a cell towards the positive terminal.

• This means that current can only flow out of one terminal and into the other terminal.

3. Current is ‘used up’ by lightbulbs 

Students intuitively think that current must be ‘consumed’ by an electrical device because charge is ‘used up’. After all, in common speech, we talk about a device having a ‘dead’ battery which must be ‘re-charged’. This reinforces the idea that a battery or cell must have become ‘empty’ as current is ‘used up’ in the component which ‘reduces’ the amount returning to the battery or cell.

When a circuit is switched on, the rate at which charge flows, i.e. the current, is the same everywhere in the circuit.

• This means the rate at which charge flows into a lightbulb is the same as the rate at which charge flows out of a lightbulb.

• Whilst current (the number of charges flowing) doesn’t change, energy is transferred from the electrons to the lightbulb

• Therefore, while the current remains the same, the amount of energy an electron has as it flows out of a lightbulb is less than it has when it flows into the lightbulb.

Top two misconceptions about heat and temperature

1. Heat and temperature are the same

Students often confuse heat and temperature, as they are used to mean the same thing in common speech; for example, 'heat it up' and 'warm it up'.

The two quantities are closely related, as an increase in thermal energy usually results in a temperature rise.

• Heating refers to the flow of energy from an object at a higher temperature to an object at a lower temperature.

• Temperature is a measure of the average kinetic energy of the particles in an object.

2. Heat rises

This is a common misconception perpetuated by students and teachers alike. Particularly in the early school years, when describing convection, the simplest way to describe what is happening is often to say ‘heat rises’.

In reality, it is the particles in the substance that rise.

• When a substance is heated, energy is transferred to the particles in it, causing them to move faster and spread out. 

• As the particles spread out, the density of the substance decreases.

• Since the mass of the substance doesn’t change, it expands (its volume increases).

• The particles in the substance rise.

How do you tackle misconceptions in physics?

We develop misconceptions because of our observations and experiences in day-to-day life. Then, when we are faced with unfamiliar situations, our brains try to come up with a solution based on what we believe to be true, which may be a misconception. It is therefore important to tackle misconceptions, which may be extremely deep-seated.

My top five strategies for tackling misconceptions as a GCSE student are:

1. Use exam questions to identify misconceptions

I firmly believe in the use of past exam questions as a tool to identify misconceptions and gaps in knowledge. 

The benefits of doing this are:

• You will develop an understanding of the knowledge examiners are looking for. 

• You can focus on the concepts that you understand the least.

• You will learn the language of the exam paper.

Our exam-style questions are written with these aims in mind and will therefore help you to identify misconceptions as well as improving your ability to answer exam questions.

2. Be open to challenging misconceptions

We are all vulnerable to misconceptions, even teachers will have a few! In my experience, the most important factor in tackling misconceptions is to be open to the fact that you will have some. Then the work to address them can begin. Be open to discussions with your teachers and your peers. Ask lots of questions. If you are unsure about anything, ask your teacher, ask your friends, read around on the topic until you feel confident in your understanding. And if your understanding is different to someone else's try to find out who has the misconception, what the misconception is, and what the correct answer is. This kind of rigorous interrogation of your knowledge will gain you a much deeper understanding of the subject as a whole.

If you want to overcome misconceptions, you must be:

• willing to confront your current ideas

• open to accepting new ideas.

3. Don’t be afraid to make mistakes

No matter where you are in your learning process, whether you’re in class or in the final stages of revision, you will get answers wrong sometimes, and that’s ok! I have seen many students lose interest in science after unexpectedly receiving a low mark, and many students have an inherent ‘fear of failure’ in general. 

As a teacher, I always emphasise that the best learning happens when we:

• make mistakes

• reflect on where we went wrong

• evaluate where there might be gaps in our knowledge.

4. Build a bank of revision aids that work for you

Some topics in physics can be very abstract and difficult to visualise. For example, we can’t see atoms or electrons, so concepts such as electricity or radioactivity can be more difficult to understand.

Often, models, analogies and diagrams are useful, but only if a student can connect with them. My advice is:

• When you find an explanation or a visual aid that resonates with you, keep a note of it to refer back to.

• Try a variety of formats; for example, a good animation or video of a process in action can give you a new perspective to visualise it in a way that you hadn’t before.

5. Try different revision techniques

Everyone learns differently and no single method of revising is better than the others. You simply have to find the best method for you. I have seen many students struggle to overcome misconceptions because of the sheer volume of information they have to learn, which causes them to shut down. 

You may learn best by:

• watching or reading information

• listening to a video or podcast

• saying information out loud

• doing hands-on activities, like making models

• doing a combination of the above.

The key is to find the revision technique that suits you and then to use it regularly and in small bursts.