energy in food

As food burns it releases energy. This energy can be used to heat up water. If you know how much water you used, and how hot it gets, you can calculate the food’s energy content. To record the temperature change, you may find it easier to use a temperature sensor connected to the computer

What you need
Clamp, stand, boiling tube, balance, food (e.g. a peanut), a mounted needle, interface, temperature sensor.

Connect the temperature sensor to the interface.
Weigh the food sample and add 30 cm3 water to the boiling tube.
Start the sensing software. Set up the software to record for 5 minutes. Heat the food in a Bunsen flame to light it. Heat the tube of water with the burning food until it has completely burnt. Re-light the food if necessary.

Questions

• How does the graph tell you how much energy is in the food?
• Did the food give all of its energy to the water?
• Use the software to read temperature values from the graph.
• Did your food extinguish before burning? Did the water lose heat as a result? How could this affect your results?
• Did you burn equal amounts of each food? If not, how will you compare the results from different foods?
• Use a spreadsheet to help with any calculations you need to do. (The IT in Secondary Science book exemplifies this.)
• Teacher note: if the food stops burning too soon, the graph will show how much heat is lost by the water. You can then account for this temperature change in your calculations.