IELTS Task 1 Process Diagrams: Passive Voice and Sequencing Words

A process diagram asks you to describe how something is made or how something happens, and the two tools that carry the whole answer are the passive voice and a small set of sequencing words. Use the passive for stages where the action matters more than who does it, and link the stages with words such as "first", "then", "after that" and "finally". Everything else is detail.

Why process diagrams feel different from charts

A line graph or a bar chart gives you numbers, so the language is about change and comparison. A process diagram gives you no numbers at all. It gives you stages, usually shown with arrows, and your job is to explain the order and what happens at each stage.

That changes the grammar you need. You are not describing a trend, so tenses like "rose" and "fell" disappear. Instead you describe a fixed sequence, almost always in the present simple, because a process is a general fact, not a past event. For a natural cycle, such as the life cycle of an insect or the water cycle, the same rule applies. For a manufacturing process, you will mostly be describing actions done by people or machines, and that is exactly where the passive voice earns its place.

One thing to keep in mind from the start: Task 1 asks for at least 150 words, and the Task Achievement criterion rewards a clear overview plus accurate detail. For a process, the overview is the number of stages and the start and end points. Do not skip it.

When the passive is the right choice

In a process diagram the doer is usually unknown, obvious or unimportant. Nobody cares which worker moves the bricks. The reader cares that the bricks are heated. So the passive is natural:

The clay is mixed with water and then cut into blocks.

Compare that with the active version, which forces you to invent a subject:

Workers mix the clay with water and then they cut it into blocks.

The second sentence is not wrong, but it adds people who are not in the diagram, and it makes your writing repetitive. The passive keeps the focus on the material moving through the stages.

Use the active voice when something happens on its own, with no outside doer:

The water evaporates and rises into the air.

Here "evaporates" cannot be made passive, because the water does it by itself. This is the most common grammar slip in process answers: writing "the water is evaporated" for a natural cycle. If nobody or nothing acts on the water from outside, keep the active verb.

A quick test helps. Ask: "Is something being done to this object, by a person or machine?" If yes, use the passive. If the object does it by itself, use the active.

The passive form, done accurately

The present passive is "is/are + past participle". Two details trip people up.

First, agreement. A singular subject takes "is" and a plural subject takes "are":

The grapes are picked by hand and are then transported to the factory.

Second, irregular participles. "Is cut", "is put" and "is ground" do not add "-ed", and "is broken", "is taken" and "is given" change form. A wrong participle in a sentence that is otherwise a good example of complex grammar still counts as an error under Grammatical Range and Accuracy, so check the verbs you use most.

You can also add the doer with "by" when it matters, for example when a machine or a named tool is part of the point:

The mixture is crushed by a large rotating drum.

Use "by" sparingly. If every sentence ends with "by a machine", the answer reads like a list.

Sequencing words that do real work

Sequencing words show order, and a process answer needs them because the diagram is all about order. A short toolkit is enough:

• Opening the process: "The process begins with…", "First,…", "At the first stage,…"
• Moving on: "Next,…", "Then,…", "After that,…", "Following this,…", "Once this is done,…"
• Showing two things at once: "Meanwhile,…", "At the same time,…"
• Closing: "Finally,…", "In the last stage,…", "The process ends when…"

Two cautions. One, do not start every sentence with a sequencing word. A paragraph in which every line begins "Then" or "Next" is monotonous and shows little range. Two, mix in linking structures that join two stages inside one sentence:

After the beans are roasted, they are cooled and then packed into sacks.

Once the liquid has been filtered, it is heated until it thickens.

Notice the tenses: "once the liquid has been filtered" uses the present perfect passive, which is correct for something completed before the next stage begins. This is a simple way to show tense range without leaving the present time frame.

A clear structure for the whole answer

A reliable shape has four parts:

1. Introduction. Paraphrase the title in one sentence. If the diagram shows how paper is recycled, write that the diagram illustrates the way in which used paper is turned into new paper.
2. Overview. One or two sentences: how many stages there are, and where the process starts and ends. For example, you can say it has six stages, beginning with the collection of used paper and ending with the delivery of the finished rolls.
3. Body paragraph 1. The first half of the stages, in order.
4. Body paragraph 2. The second half of the stages, in order.

Count the stages before you write. If the diagram has eight stages, you can give each a clause and finish within the word range. If you are tempted to explain the science behind a stage, stop. Task 1 wants what the diagram shows, not outside knowledge.

Mistakes that cost marks

Mixing past and present. A process is a general description, so use the present simple throughout. Switching to the past tense halfway through is a frequent slip.

Overusing "then". Replace some with "after that", "next" or a linking clause, as above.

Adding information that is not in the diagram. If the diagram does not say the temperature, you cannot say it. Describe only what is shown.

Ignoring the overview. Without a statement of the number of stages and the endpoints, the Task Achievement criterion is hard to meet, however good the grammar is.

Copying labels word for word. The labels are useful, but swap some into other forms. If the label says "crushing", you can write "the material is crushed". That is paraphrase, and it also gives you a natural reason to use the passive.

Forgetting the stages that loop. Some diagrams show a cycle or a step that returns to an earlier stage. Say so explicitly, for example "the water is then returned to the tank and the cycle begins again".

A short practice routine

Take one process diagram from an official Cambridge practice book and set a timer for 20 minutes, which is the usual allowance for Task 1 inside the 60-minute Writing test. Write your answer, then do three checks: count the stages in your text against the diagram, underline every passive verb and confirm each one has a correct participle, and circle every sequencing word to see whether you leaned on one too often. Then rewrite only the weakest paragraph and compare the two versions. One focused rewrite teaches more than three rushed new answers.

Where Toey fits

I built Toey's IELTS Writing grading so you can check a Task 1 answer like this and see feedback on grammar and structure within a few minutes. The free plan includes 1 Writing task graded per week, so you can test it on a single process diagram without paying. It is web only for now, and the AI grade is an estimate that helps you spot patterns, not an official band. Judge your corrections against the published band descriptors, and use the feedback as a second pair of eyes.

Checked on 7 November 2026

Ready to practise? Try IELTS Writing on Toey