What is the aim of using this activity?

This tool is designed to diagnose whether students distinguish strength from concentration. For students who are unsure, the activity gives them practice in differentiating the two concepts by being able to 'view' solutions of weak/strong and concentrated/dilute and their differences at the particle level.

Some able students may indeed find this activity easy and it is useful to reinforce their ideas of strong/weak and the distinction with concentration.

What is the benefit of using this type diagnostic tool for formative reasons?

It is beneficial to check student learning, to provide ongoing feedback for teachers to improve their teaching and to students to improve their learning, as for any formative assessment. Students are helped to recognise their strengths and weaknesses, and identify any problems or areas that need developing further. It is beneficial for the teacher to get swift feedback to enable them to find out more about areas of student difficulty requiring attention.
 

Are there certain types of learner that may find these diagrams particularly helpful?

Visual learners may find these representations helpful in clarifying their ideas about what is happening on the sub-microscopic level. The diagrams are simplified representations, aimed at highlighting particular features of the system represented. Some students may require a bit more time to familiarise themselves with the types of particles drawn and how they have been drawn here.