Calorimetry

Calorimetry

Calorimeter: A device used to measure the heat released or absorbed during a chemical or physical process occurring within it
Therefore, calorimetry is the study of energy changes during a physical and chemical process, while using a calorimeter

Using a Simple Calorimeter

• A simple calorimeter is made up of two stacked vessels covered by a lid with holes for the thermometer and stirrer

• The inside vessel is filled with a known mass of water

  • The vessels are both strong insulators to help prevent thermal energy from escaping

    • However, some still does due to the holes in the cup for the stirrer and thermometer

• Since some gas can escape, this calorimeter measures the energy changes at a constant pressure

Assumptions about Calorimeter

A simple calorimeter measures the temperature change of the water in which a process such as a chemical reaction is occurring

What assumptions must be considered about a calorimeter:

When measuring this, some assumptions need to be considered;

1) The system is isolated (thermal energy exchanged with outside surroundings is ignored)
2) Thermal energy exchanged between the objects within the calorimeter is ignored
3) If something dissolves in the water, the solution will retain the same properties (density and heat capacity will be the same)
4) The process is under constant pressure

Once the assumptions are applied, the following equations apply

How to use a simple calorimeter

• Ensure that all water inside is equilibrated. Measure initial temperature

• Add reactants to the calorimeter
  Allow the reaction to proceed. Stir to maintain an even temperature throughout. Record any changing temperature

• For an exothermic reaction, the final temp is the maximum temperature

  • For an endothermic reaction, the final temperature is the minimum

Using Calorimetry Data

• The water in the calorimeter absorbs or releases the energy in the experiment

• As a result, you can use Q = mc∆T

  • If the solution is dilute, you can assume that the specific heat capacity is the same as water

  • If not dilute, then the specific heat capacity decreases