Calculating Energy Released and Absorbed

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<h3>Calculating Energy Released and Absorbed</h3>

Every chemical reaction either absorbs or releases energy. Energy is described in kilojoules per mole, which is a unit of measurement reflecting the amount of energy stored within a material. To determine how your chemical reaction is using energy, you will need to take specific measurements of the reaction itself, then calculate those values using a standard equation. These steps are recommended for those with a basic understanding of working with chemical reactions. Make sure that you are wearing proper safety equipment and that you are familiar with the chemicals being used.

Step 1

Research the specific heat capacity value for your first reactant. See the Resource links for lists of the heat capacities of many common substances.



Step 2

Fill two separate containers with the reactants. Weigh each container to determine the mass of the reactant. Record these measurements in grams.

Step 3

Measure the temperature of the first reactant with a thermometer. Record this measurement.

Step 4

Add the second reactant to the first container. Measure the temperature of the combined reactants. Record this value.

Step 5

Insert the measurements taken from the previous steps into the following equation:



Energy = (mass of first reactant + mass of second reactant) x Specific Heat Capacity x (temperature of first reactant – temperature of combined reactants)

This equation will calculate the number of kilojoules per mole released by the first reactant. To determine the energy absorbed, assign a negative value to the equation’s solution.

Things Needed

  • Two or more chemical reactants
  • Two or more chemistry containers (flasks, beakers, etc.)
  • Standard lab thermometer
  • Notepad and pen
  • Calculator (recommended)
  • Safety goggles and gloves
Dave Pennells

By Dave Pennells

Dave Pennells, MS, has contributed his expertise as a career consultant and training specialist across various fields for over 15 years. At City University of Seattle, he offers personal career counseling and conducts workshops focused on practical job search techniques, resume creation, and interview skills. With a Master of Science in Counseling, Pennells specializes in career consulting, conducting career assessments, guiding career transitions, and providing outplacement services. Her professional experience spans multiple sectors, including banking, retail, airlines, non-profit organizations, and the aerospace industry. Additionally, since 2001, he has been actively involved with the Career Development Association of Australia.