What should be done after measuring the temperature in the polystyrene cup?

After measuring the temperature in the polystyrene cup, placing a lid on the cup and then putting it in a beaker is important for maintaining the accuracy of the temperature measurement. The lid serves to minimize heat loss to the environment during the experiment, which is particularly relevant for reactions that are sensitive to temperature changes, such as exothermic or endothermic reactions.

Using a beaker further helps to insulate the cup and stabilize the temperature conditions; this setting reduces the influence of external factors like drafts or temperature fluctuations in the surrounding air. Such precautions help ensure that any observed temperature changes are primarily due to the reaction occurring within the cup, thereby improving the reliability of the results collected.

Taking the cup out of the beaker would expose the reaction to environmental conditions that may lead to inaccuracies in results. Comparing results with previous data could be insightful but does not directly aid in the immediate experimental process. Repeating the experiment without a lid would counteract the purpose of controlling temperature changes and could lead to misleading results.