Academic Writing Task 1 · process diagram

A diagram illustrating the functional components and operation of a hot air balloon

The picture below shows how a hot balloon works.

Summarise the information by selecting and reporting the main features, and make comparisons where relevant. Write at least 150 words.

The operational mechanism of a hot air balloon

1.Propane is mixed with air in the burner to produce a flame
2.The flame heats the air inside the envelope
3.Hot air becomes lighter than the surrounding cool air
4.The balloon rises due to the density difference
5.The parachute valve allows hot air to escape at a controlled rate to manage descent

Chart redrawn by BandLadder from the data in the original IELTS practice task. Many IELTS practice tasks come from the Cambridge IELTS series (Cambridge University Press & Assessment); all rights in the original tasks remain with their owners.

Band 8 sample answer

The provided diagram illustrates the structural components of a hot air balloon and explains the underlying physical principles that allow it to operate. The system relies on a combination of specific hardware and the density difference between heated and ambient air.

Structurally, the balloon consists of an envelope, which is the main body, constructed from panels and gores. At the top of this envelope is a parachute valve, described as a self-sealing flap designed to release hot air at a controlled rate. Below the envelope, a skirt connects to the burner and basket assembly. The burner is supplied by a propane cylinder, which provides the fuel necessary to heat the air inside the envelope.

Regarding the operational mechanism, the burner mixes propane with air to generate a flame. This process heats the air within the envelope, making it lighter than the surrounding cool air. This density differential creates the lift required for the balloon to ascend. Conversely, by manipulating the parachute valve to release hot air, the pilot can control the rate of descent. Overall, the balloon functions as a controlled thermodynamic system where fuel combustion regulates buoyancy.

188 words. Every figure in the answer comes from the chart above.

How to write about process diagrams

Say how many stages there are and where the process starts and ends.
Use the passive and sequencers: first, after this, once, finally.
Keep every stage; a missing step costs task achievement.

structural components: the various physical parts that make up something
underlying principles: the fundamental rules or laws that explain operation
density differential: the difference in mass per unit of volume
combustion: the process of burning something to produce heat
conversely: introducing a statement that reverses the previous idea
manipulating: handling or controlling something in a skillful manner

Write your own report and get a band

Take a timed Academic writing test and get a band for task achievement, coherence, vocabulary and grammar, with the sentences to fix.

Practise IELTS Academic writing

On your phone? Get the BandLadder app.

Frequently asked questions

What should the overview say?

The diagram illustrates the structural components of a hot air balloon and explains the thermodynamic principle of buoyancy that enables it to ascend and descend.

How long should an IELTS Task 1 answer be?

At least 150 words; 170 to 200 is the safe range. Spend about 20 minutes on it and leave 40 for Task 2, which carries twice the marks.

How do I describe process diagrams?

Say how many stages there are and where the process starts and ends. Use the passive and sequencers: first, after this, once, finally. Keep every stage; a missing step costs task achievement.