This came in the London March 2014 exams and many students struggled to get higher than 6.5. Since there are a lack of resources on the internet to help answer this question, my students have asked me to share this sample answer. Again, I must stress that you have any online sample answers verified and checked by an actual examiner or IELTS trained tutor before studying it. If you’re an IELTS teacher, please remember to teach the language techniques of a process diagram so that they don’t memorise answers.
The diagram below shows how a hot air balloon ascends and descends.
Summarise the information by selecting and reporting the main features and make comparisons where relevant.