How to answer science exam questions: Describe vs Explain Command words
Command words are commonly used in exams as they tell the student how to answer science exam questions. Two of the most commonly used command words are “describe” and “explain”.
To ensure you gain top marks in your exams, it is important that you understand the differences between these two terms. This will help you draft an appropriate answer.
When you are asked to describe something, you should simply ‘say what you see’. But, if you are asked to explain something, you should give a scientific explanation in your answer. This means that you should expand on “how” and “why”, using the word “because” in your answer.
Here’s an example. To describe what happens when we exercise, you would simply say the heart rate would increase and the body would start to heat up and produce more sweat. But, if you are asked to explain what happens when we exercise, you would say that the heart rate increases because the muscles need more oxygen. And we sweat more as the body heats up. You will then go on to explain that sweating is a mechanism the human body uses to stabilise its temperature.
Now, let’s look at some more examples regarding the use of the command words “describe” and “explain” in scientific-based questions.
Describe
In a science exam, you might be asked to “describe” a biological system or a molecule. Or you might be asked to describe the function of such a biological system or cell (e.g. blood cells). In the first case, you should simply talk about what you might see if you had the molecule in front of you (for example from a book’s image). In the second case, when you are asked about describing the function, you should talk about the main roles of the biological molecule in the system it is involved in.
Let’s look at this example from the 2018 AQA combined science higher-tier specimen paper.
Q1a. Blood is made up of four main components. Red blood cells and white blood cells are two of these components. Describe the functions of the two other components of blood [2 marks].
Ans: The other two components of blood are plasma and platelets. Plasma is the component where blood cells are suspended [1 mark] and platelets are involved in blood clotting [1 mark].
You can see from the example above that you need to say the two components of blood that are not mentioned in the question. Then, just say the role that element has in its natural environment. I.e. platelets are involved in blood clotting where blood clotting is the natural role of platelets.
Explain
You could also be given the exact same question as above and instead asked to Explain the functions of the two other components of blood [2 marks].
Here’s how you would answer the question.
Ans: Plasma constitutes half of the blood volume and is in a liquid form because it allows all the nutrients present in the blood to be easily transported to the body tissues and organs [1 mark]. Platelets are involved in blood clotting because they have surface proteins which make them stick together. This mechanism enables platelets to clump together breaks in a blood vessel [1 mark].
In this answer, the mechanism and action of plasma and platelets are explained by answering the questions taking into account the why and how. Note that a proper answer should include concepts introduced by the word “because” to enable you to expand on your answer. The question about plasma explains how this blood component is able to meet its main function. It explains why nutrients are able to be transported thanks to plasma’s liquid form. As for platelets, the answer shows the mechanism by which (the “how”) these blood components are able to clump together breaks in blood vessels.
Hopefully, you now have some understanding of how to answer science exam questions that has the command words ‘describe’ or ‘explain’. In the next post, I’ll show you how to answer ‘evaluate’ type questions.
