A group of students is engaged in an activity in which they are measuring the boiling temperature of ordinary tap water in a beaker.
Which of the following is not a suitable indicator to assess them on this task ?

The correct option is Measure the boiling temperature as 100°C.

Explanation:

In a science practical activity, students are assessed on procedural skills, careful observation, correct handling of apparatus, and recording actual empirical observations rather than assuming theoretical values.

1. Pay due attention to the least count of the thermometer: This is an essential skill to assess, as knowing the least count ensures accurate reading of measurements.

2. Ensure that the thermometer does not touch the walls of the beaker: This assesses proper laboratory technique. Touching the walls or bottom of the beaker would cause the thermometer to measure the direct heat of the container rather than the liquid temperature.

3. Use a stand to suspend the thermometer: This evaluates proper equipment setup to maintain safety and steady position during heating.

4. Measure the boiling temperature as 100°C: Tap water contains dissolved impurities and minerals, and local atmospheric pressure may vary, so its boiling point is rarely exactly 100°C. Assuming or forcing the recorded value to be precisely 100°C without actually observing and reading the thermometer correctly promotes bias rather than authentic scientific measurement.

Therefore, pre-determining or forcing the measurement to be 100°C is not a suitable indicator for assessing practical activity performance.