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DIY Colorimeter

Ever wanted to find out for yourself much energy it takes to break apart crystals or heat up a cup of coffee? Scientists use calorimeters to determine the amount of heat given off or absorbed by a given chemical reaction. It's moderately easy to build a basic calorimeter out of household items, but calibration requires a few extra steps.

Things You'll Need

  • Three Styrofoam coffee cups
  • Plastic coffee lid with flip-top closed
  • Pen or other puncturing device
  • Stirrer
  • Water
  • Metric measuring cup
  • Thermometer with Centigrade units
  • Reactants
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Instructions

  1. Assemble and Calibrate

    • 1

      Punch two holes in the plastic coffee lid -- one large enough to fit the thermometer and one large enough to fit the stirrer.

    • 2

      Measure and record a fixed mass of cold water -- 25 grams, for example -- into one Styrofoam cup. (Remember that at standard temperature and pressure, 1 mL = 1 gram.) Stack the cup with the cold water onto another Styrofoam cup. The two-cup container is the calorimeter.

    • 3

      Insert the thermometer into the cup of cold water. Write down the temperature.

    • 4

      Measure and record the same mass of hot water (25 g in the example) into the other Styrofoam cup. Insert the thermometer into the cup of hot water. Write down the temperature.

    • 5

      Pour the hot water into the cold water. Seal the lid onto the Styrofoam cup containing the water. Slip the stir rod through its hole and stir. Insert the thermometer. Read and record the temperature of the mixed water.

    • 6

      Subtract the initial temperature of the hot water from the final temperature of the mixed water to find the change in hot water temperature.

    • 7

      Subtract the initial temperature of the cold water from the final temperature of the mixed water to find the change in cold water temperature.

    • 8

      Calculate the change in heat in the hot water:

      Q(h) = m(h) x t(h) x 4.184

      where Q(h) is the change in heat in the hot water, m(h) is the mass of water in grams, t(h) is the change in temperature in the hot water and 4.184 is the specific heat of water.

    • 9

      Calculate the change in heat in the cold water:

      Q(c) = m(c) x t(c) x 4.184

      where Q(c) is the change in heat in the cold water, m(c) is the mass of cold water in grams, t(c) is the change in temperature in the cold water and 4.184 is the specific heat of water.

    • 10

      Because the change in heat of a system must add up to 0, use the equation

      0 = Q(calorimeter) + Q(h) + Q(c)

      to determine the change of heat in the calorimeter, Q(calorimeter).

    • 11

      Use the equation

      Q(calorimeter) = heat capacity(calorimeter) x t(calorimeter)

      to solve for the heat capacity of the calorimeter. Let t(calorimeter) equal the change in temperature of the calorimeter, which is the same as the change in temperature of the cold water.

    • 12

      Now that you know the heat capacity of the calorimeter you can use it to calibrate measurements of change in heat in other equations, like heat of solution of a salt.

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