In a coffee-cup calorimeter, the parameter that is kept constant is the temperature. Here's why:
1. **Explanation**: The purpose of a coffee-cup calorimeter is to measure the heat of a reaction at constant pressure. By keeping the temperature constant, any heat transfer that occurs during the reaction can be accurately measured.
2. **Example**: When a chemical reaction takes place in the coffee-cup calorimeter, the heat released or absorbed by the reaction causes a change in temperature. By maintaining the temperature constant throughout the experiment, the heat flow solely depends on the reaction occurring, allowing for accurate calculations of heat changes.
Therefore, in a coffee-cup calorimeter, it is essential to keep the temperature constant to ensure reliable and precise measurements of heat changes during a reaction.
