1 28 09 Calorimetry of Fuels and the Use of Energy to Do Work The Energy Work Connection This experiment will be done on nd rd February 2 3 in place of The System experiment Adapted by Caitlin Conn and Patrick Crooks from The Chemurgy of Peanuts by Genevieve Miller Introduction NOTE If you are allergic to peanuts please inform your instructor or TA immediately so that you can be assigned a different lab Energy is crucial to the survival of every living thing As humans our bodies need to remain within a relatively narrow temperature range We burn food internally to stay warm Additionally because all systems tend to move toward disorder without an input of energy we would die without food We need bodily fuel so that we can function and we burn it when we walk talk sleep exercise and study You may have heard of burning calories in reference to exercise Please note that calories are never burned A calorie is simply a measure of energy and that energy is actually released during a combustion reaction During exercise the body burns food to release energy and that energy can be measured in different units such as calories Combustion reactions take place within our bodies when we burn food A combustion reaction is defined in Chemistry The Central Science as a chemical reaction that proceeds with evolution of heat and usually also a flame This textbook goes on to say that most combustion reactions involve oxygen 1 Different fuels can be burned to release energy Food for example is a type of fuel burned by the body Another type of fuel with which you will use in this experiment is paraffin Paraffin is the material of candles When you burn a candle the paraffin is combusted and heat is released The energy released by paraffin combustion can be used to light or heat areas of different sizes depending upon how much paraffin is combusted You will be determining the energy released by the combustion of paraffin as part of this lab You will also examine the calorie content of a common food item peanuts If you have a peanut allergy please tell your instructor or your TA right away so that you can be assigned a different makeup lab Peanuts are used in a variety of different food items and also in substances like cosmetics and paint George Washington Carver was largely responsible for identifying the many different uses of peanuts and for using peanuts to serve many different purposes 2 To calculate the energy content of different substances you will be building your own calorimeter out of household items A calorimeter is defined as an apparatus that measures the evolution of heat 1 You will burn several substances and use temperature changes in water to determine the energy released by the combustion Then you will answer theoretical questions to help you understand the connections between calories and work You will need to use the textbooks provided for you in your classroom in order to complete some parts of this lab Please make sure to cite these sources properly 2 Background Chemistry Overview The metabolic reactions that take place inside our body are vital to our existence One of the most fundamental examples of metabolism is digestion The process of digestion is most certainly a chemical one it is an example of a combustion reaction food reacts with oxygen to generate energy Foods produce the same amount of energy whether they undergo combustion under metabolic conditions or they are burned outside the body We can then calculate the energy value of food by burning it and measuring the amount of heat that is released from the reaction To ensure accuracy chemists use calorimeters devices that measure temperature changes from chemical reactions to determine the energy produced by a reaction Food energy is measured in Food Calories with a capital C One Food Calorie is 1000 times bigger than a scientific calorie that is 1 Cal 1 kcal 1000 cal One calorie is the energy required to raise the temperature of 1 g of water by 1 C from a standard temperature at 1 atm pressure Throughout this lab we will use Calorie with a capital C to indicate Food Calories In this experiment you will measure the amount of energy released by the combustion of several different fuels The energy released during the combustion will raise the temperature of a measured volume of water in a simple calorimeter We can determine the exact amount of energy released because we know the specific heat of water The specific heat of water is 1 0 cal per g per C or 1 Cal per kg per C By measuring the temperature change in a known mass of water you can determine the amount of energy Energy released mass of H2O heated temperature increase specific heat of H2O Eqn 1 2 Paraffin Calorimetry Paraffin can be burned to release energy Typically the energy content of paraffin which is found in candles is 10 0 k cal g 3 Another word for paraffin is alkane which is a particular type of organic molecule Just as there are many alkanes there are many different kinds of paraffin Most paraffins are not very reactive at room temperature and one atmosphere pressure but they can be combusted by increasing temperature and or pressure Paraffin combustion produces water and carbon dioxide and releases energy 4 Besides being used in candles paraffin was being considered as a potential rocket fuel as of 2003 NASA noted the increased safety and decreased pollution that would result from using paraffin as an energy source 5 Paraffin is also used as a cosmetic and is frequently applied to the skin to soften it 3 Peanut Calorimetry Peanuts are known for their high energy value On average a peanut contains 6 Cal per g of energy In fact one pound of peanut butter contains the same food energy found in 32 eggs or 2 5 pounds of steak It is this energy value and the low cost of producing peanuts that led Carver to stress their importance during the Depression Peanut oil can be represented by the following molecule with molecular formula C57H104O6 Please note that at each vertex carbon and hydrogen are present Each vertex represents one carbon and hydrogens are attached so that each carbon has four bonds Figure 1 The molecular structure of peanut oil 2 The combustion reaction for peanut oil given in Figure 1 is shown in Equation 1 C57H104O6 l 80 O2 g 2 57 CO2 g 52 H2O l heat Eqn 2 Energy Conversion Energy can be measured in many different units You may need to refer to the textbooks available to you in the classroom to complete some of the questions in this lab You