A student is carrying out a practical investigation to determine the effect of stirring on the rate of reaction between marble chips and hydrochloric acid. Describe the observations and measurements that the student should make to ensure accurate and reliable data.

1. Before the reaction starts the student records the mass of the marble chips and the volume of HCl used, noting the initial temperature of the acid.
2. During the reaction the student records the time taken for the gas to reach the end of a calibrated gas syringe or the volume of CO₂ produced, and notes any temperature change of the solution.
3. After the reaction the student records the final mass of the remaining solid, the final volume of gas, and the final temperature, checking that the reaction has ceased.
4. The student takes precautions such as using a calibrated balance, a calibrated gas syringe, stirring at a constant speed, and performing the experiment in triplicate to ensure accuracy and reliability.