Calorimetry Lab

We will explore the concept of calories as units of energy and learn about food calorimetry. Calorimetry is a technique used to measure the energy released or absorbed during a chemical reaction or phase change. By applying calorimetry to food samples, we can determine the number of calories per gram of food. In this experiment, we will burn food samples and measure the energy released by heating water. This will allow us to calculate the energy content of the food samples and compare it to the information provided on their nutrition labels.

Safety Measures

·         Wear safety glasses or goggles throughout the experiment.

·         Handle fire and burning food samples with caution.

·         Check for food allergies among the participants before using food samples. Individuals with sensitivities or allergies should not participate in activities that may expose them to potential allergens.

·         Do not eat or drink in the lab.

Objectives

·         To understand the concept of calories as units of energy and their relation to food energy.

·         To explore the principles of food calorimetry and its application in determining the energy content of food samples.

·         To learn how to use a calorimeter to measure the energy released during the combustion of food samples.

·         To calculate the energy content of food samples in calories and kilocalories per gram.

·         To compare the experimentally determined energy content of food samples with the information provided on their nutrition labels.

·         To calculate the percent error between the experimentally determined energy content and the calculated value from the nutrition label.

·         To analyze and interpret the results obtained from the calorimetry experiments and draw conclusions about the energy content of different food samples.

·         To develop skills in following laboratory procedures, handling equipment safely, and recording and analyzing experimental data accurately.

Materials

·         10 ml round bottom flask

·         Calorimeter

·         Clamp for flask

·         Clamp for thermometer

·         Wire Mesh

·         Thermometer

·         Stir rod

·         Graduated Cylinder, 10 mL

·         3 Dry Food Samples with Nutrition Labels

·         DI Water

·         Bunsen burner

·         Aluminum Foil

·         Electronic Balance

Perform Open Air Calorimetry

1.       Using a graduated cylinder, measure 10 mL of water and carefully pour it into the beaker.

2.       Determine the mass of the water and record the value in the data table (density of water = 1 g/mL).

3.       Place aluminum foil under your workspace to protect the surface.

4.       Set up the calorimeter and Bunsen burner on the aluminum foil. Place the wire mesh on the platform.

5.       Obtain a food sample weighing approximately 2 grams.

6.       Determine the initial mass of the food sample and record it in the data table.

7.       Place the food sample on the wire mesh.

8.       Ensure the workspace is clear of flammables.

9.       Suspend the thermometer inside the beaker a centimeter above the bottom. Record the initial temperature of the water in the data table.

10.    Carefully light the Bunsen burner and use it to ignite the food sample.

11.    Allow the burning food sample to heat the water in the beaker. Periodically stir the water gently with the stir rod.

12.    Monitor and record the highest observed temperature change of the water in the data table.

13.    Once the food sample has burned completely, find the mass of the remaining food sample. Record this value in the data table.

14.    Repeat steps 1 to 13 for the remaining food samples.

Calorimetry Calculations for Each Food Sample 

15.    Determine the mass of water in grams (ml = g water) and record it.

16.    Cp (specific heat) of water = 1 cal/g/°C.

17.    Determine the change in temperature (∆T) of the water and record it.

18.    Calculate the energy (Q) using the formula Q = mCpΔT.

19.    Record the value of Q in calories.

Use the following formula: Q = mCpΔT

Q = calories

m = Mass of Water (g)

Cp = Specific Heat (cal/g/oC)

ΔT = Change of Temperature (oC)

Kilocalories/Gram Calculations for Each Food Sample

20.    Determine the number of kilocalories (food Calories) released by the burning food sample (1 kilocalorie = 1,000 calories). Record the value.

21.    Calculate the mass of the food consumed during burning (initial mass of food - final mass of food). Record the value in grams.

22.    Calculate the energy content of the food in kilocalories/gram (answer from step 20 / answer from step 21). Record the value.

23.    Use information from the nutrition label of the food sample to calculate the kilocalories/gram (divide Calories per serving by the number of grams in a serving). Record the value.

24.    Calculate the percent error by comparing your experimentally determined energy content (in kilocalories/gram) to the calculated value from the nutrition label using the formula: %error = (|(Actual Value - Experimental Value) / Actual Value|) * 100. Record the value.

25.    Repeat all equations and calculations for each food sample measured.

26.    Enter all recorded values in the table below.