Objective To determine the stored energy in peanut and biscuit by calculating the temperature change of water. Hypothesis The calorie of peanut is higher than taht of biscuit. Principle of method Burn food samples under a boiling tube containing a measured amount of water. Measure the temperature increase in the water. Calculate the amount of energy needed to cause that temperature increase. This gives an estimate of the amount of energy stored in the peanut and biscuit . In the experiment, water is placed in the boiling tube.
When a particular food item will be ignited under the boiling tube, the water above will absorb the heat, thereby causing the temperature (T) of the water to increase. By measuring the change in temperature (? T) of a known volume of water, the energy gained by the water can be calculated by using the formula as follows: E = mc? T where E is the heat gained in calories (cal); m is the mass of water in grams (g); c is the specific heat capacity of water (1 calorie/g °C); and ?
T is the change in temperature in degrees Celsius (°C). In the experiment, the independent variable is the different types of food used and the dependent variable is the temperature change of water. The controlled variables are the weight of food and the volume of water. Also, we assume that the heat gained by the water will equal to the heat lost by the food. Procedure 1. Cut up a range of foods into small pieces – around 1 cm square or 0. 5 cm cubed. (with the same mass) 2.
Weigh the pieces of food to obtain the same weight by using the balance . 3. Use the measuring cylinder to measure 20 cm3 of water into the boiling tube. 4. Clamp the boiling tube to the clamp stand. 5. Measure and record the initial temperature of the water with the thermometer. 6. Impale the piece of food carefully on a mounted needle. 7. Light the Bunsen burner and hold the food in the flame until it catches alight. (Precaution: Wear safety spectacles when using Bunsen burner. ) . Hold the food under the boiling tube until the food has burnt completely and the flame has gone out. (Precaution: If the flame goes out, but the food is not completely burnt, quickly light it again using the Bunsen burner and replace the food under the tube. ) 9. Measure and record the temperature of the water again. 10. Repeat the steps 3 to 9 for other foods. 11. Calculate the rise in temperature each time. 12. Calculate the energy released from each food by using the formula.