Question

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Enthalpy of Fusion of Ice

This worksheet will help you organize your thoughts for the discussion. Write down some notes based on the questions and prompts below. 1. Describe the parts of a coffee cup calorimeter. In your description, specify the use of each part. 2. Outline how you would use a calorimeter to determine the enthalpy of fusion of ice.

Answer 1

Question 1.

A coffee cup calorimeter is a constant-pressure calorimeter. As such, the heat that is measured in such a device is equivalent to the change in enthalpy. A coffee cup calorimeter is typically used for solution-based chemistry and as such generally involves a reaction with little or no volume change. Therefore, while the heat is exactly equal to the enthalpy change ($\Delta$H) in this case, it will also be approximately equal to the change in the internal energy ($\Delta$U) since the work will be very small (assuming there are no gas reactants or products).

The more technical name for this type of calorimetry is isobaric calorimetry. The "coffee-cup" name comes from the fact that most of the time this experiment is done inside of a simple styrofoam cup. A styrofoam cup makes for a good adiabatic wall and helps keep all the heat released or absorbed by the reaction inside the cup so we can measure it.

The diagram of the coffee-cup calorimeter can be drawn as follows.

styrofoam cup system is dissolved in the water coffe-cup calorimeter