R1.1.5 Practical considerations Notes

Practical Considerations in Calorimetry

Experimental Setup for Calorimetry

1. In a typical school laboratory, calorimetry is performed using a coffee-cup calorimeter or a metal calorimeter.
2. These setups are relatively simple and rely on the principle that the heat released or absorbed by the reaction is transferred to a surrounding medium, typically water.
3. The temperature change of the water is then measured to determine the heat transferred.

Key Components of a Simple Calorimeter

1. Insulated Container: Often a polystyrene cup, used to minimize heat loss to the surroundings.
2. Thermometer or Temperature Probe: To measure the temperature change ($ \Delta T $) of the water or solution.
3. Reaction Vessel: The container where the reaction occurs (e.g., a metal can for combustion reactions).
4. Stirring Mechanism: Ensures even distribution of heat throughout the water.

Sources of Error in Calorimetry

1. While calorimetry is a powerful tool, it is not without limitations.
2. Several factors can introduce errors into the measurement of heat changes, leading to discrepancies between experimental and theoretical values.

1. Heat Loss to Surroundings

1. Even with insulation, some heat inevitably escapes from the calorimeter to the surroundings.
2. This means the temperature change measured by the thermometer is less than the actual temperature change, leading to an underestimation of the heat transferred.

2. Incomplete Combustion

1. In combustion reactions, the fuel may not burn completely, especially if there is insufficient oxygen.
2. This results in less heat being released than expected.
3. For example, instead of forming carbon dioxide ($ CO_2 $), incomplete combustion may produce carbon monoxide ($ CO $) or soot ($ C $).

3. Assumptions About Specific Heat Capacity