A word of warning on teaching tricks

In Science, students are expected to remember quite a few facts and then apply these successfully to new contexts. This can be difficult for quite a few students, particularly those that are not very motivated or struggle with their recall.

As teachers, we want our students to succeed and feel successful. Is it any wonder then that we have formula triangles to help students use equations, songs to remember facts and acronyms to recall steps in explanations?

I have used all of these in the past and still use acronyms (eg. PANIC for Chemistry). Many people are now against using formula triangles and rightly so. They don’t allow students to actually practise any maths (that they are certainly taught in Maths lessons) and they add to the cognitive load of students by expecting them to remember which term goes where in the triangle and how to use them.

I want to explore using acronyms for explanations in this post using the example of variables in Science.

Students need to know the meaning of the terms ‘independent’ ‘dependent’ and ‘control’ variable and then correctly identify these in investigations. Throughout my years in teaching, I have come across a few acronyms to help students rememeber which is which. One of these is Dairy Milk Ice Cream, with each letter representing: Dependent Measure Independent Change.

I have been using this acronym to no avail. Why can’t students work out what the independent variable is in this question: ‘A scientist is investigating the effect of light intensity on the rate of photosynthesis‘ using this acronym?

It is because they have little understanding of what that sentence actually means. Students are trying to decipher the meaning of the words ‘light intensity’, ‘rate’ and ‘photosynthesis’ whilst also understanding the meaning of the word ‘effect’, which a number mix up with ‘affect’.

And then I give them an acronym to use and suddenly they are experiencing cognitive overload trying to work out what the variables even are in that statement let alone determine if they are independent, dependent or control!

So what do we do? I think it is important we do the following:

Step 1: Define the word variable

I say that a variable is something that can change and have different values. If I want to see if the amount of water I give to a plant will affect its growth, a variable would be the ‘amount of water’ or ‘plant growth’. A plant (on its own) is not a variable. Water is not a variable.

Giving lots of examples and non-examples in this way ensures two things:

• students get a better understanding of what a variable is and isn’t
• students learn how to name variables correctly. So simply saying ‘water’ is not a variable but ‘amount of water’ is.

Step 2: Describe the variables in terms of independent, dependent and control always in context

Each time we come across an investigation in a topic (PAGs in OCR or Required Practicals in AQA), we need to be explicit about what the variables are and identify them as independent, dependent or control.

For example, when teaching the ‘effect of temperature on the rate of a reaction’, I ask students to tell me what the scientist is deciding to test. Most can tell me that the scientist is testing temperature to see what the effect is on the rate of a reaction. I explain that when a scientist tests something like this, they need to test a range of values to see what the effect is. In this example, the scientist will test a number of different temperatures to see how it affects the rate of a reaction.

I identify the dependent variable first because of the meaning of the word. I say: in this investigation, by changing the temperature, the scientist is trying to see how the rate of reaction is affected. So the rate of reaction depends on the different temperatures. This makes the rate of reaction the dependent variable. A scientist needs to observe or measure this variable so they can find out if it has been affected by the temperatures they are testing.

Then, I discuss the independent variable. As the scientist is testing different temperatures in this investigation, this makes it the independent variable. It is one the scientist is changing to see if it has an effect.

And then, I talk about all the variables that need to be controlled. If you are interested in a superb explanation for how to introduce variables, Springboard KS3 Science has one of the best ways to do so.

Why the word of warning?

Teaching tricks are useful if the purpose of teaching is to help students pass an exam. This is why teachers use formula triangles and acronyms and unrelated examples (such as comparing a root hair cell to Mr Men as described in this post).

If viewed solely through that lens, recall of facts without context or meaning is acceptable. But that is not why we teach. Yes, good results in exams are important. Having an understanding of our subject is more so.