Biomass Calorimeter Energy from Biomass

Transcription

1 Biomass Calorimeter Enery from Biomass Introduction Have you ever noticed the nutrition label located on the packain of the food you buy? One of the first thins listed on the label are the calories per servin. Did you know that the Calorie is the unit used to measure enery? In this lab you will measure how much enery is contained in various biomass samples. Backround The law of conservation of enery states that enery cannot be created or destroyed, only converted from one form to another. This law was used by scientists to derive new laws in the study of heat enery, temperature, and heat transfer. The First Law of Thermodynamics states that the heat enery lost by one body is ained by another body. Biomass materials contain stored enery. Burnin these materials is a way of measurin their enery content. In this experiment, you will measure the amount of enery released from a known mass of biomass material by measurin the chane in temperature of a known volume of water. A homemade calorimeter is used to measure the chane in temperature of water caused by the absorption of the heat released by burnin various biomass materials. You will record the chane in temperature of the water, chane in mass of the biomass material, and calories and British thermal units produced. Common units of heat measurement are British Thermal Units (Btu) and calories (cal). A Btu is the standard unit of enery used to measure the heat content and enery value of fuels. A calorie is the amount of heat required to raise the temperature of 1 ram (1 milliliter) of water 1 deree Celsius. In other words, it takes one calorie of enery to raise the temperature of one ram of water by one deree Celsius. Knowin this, the amount of enery locked in a sample of biomass can be calculated if the temperature chane is measured. (note: The normal unit for measurin the enery content in food is called a Calorie (with an uppercase C). A Calorie is really a kilocalorie, or 1000 calories (lowercase c).) When biomass bums, its stored enery is quickly converted into heat enery. The heat enery that is released is then transferred into the water above it in the calorimeter. The temperature chane in the water is then measured and used to calculate the amount of heat enery released from the burnin biomass. The heat enery is calculated usin Equation 1 Q = mcδt Equation 1 Q = heat enery m = mass of the water C = specific heat of the water ΔT = chane in water temperature, T final - T initial (Δ is the Greek letter Delta which means chane in ) Safety Precautions You must wear safety lasses durin this experiment. DO NOT use flame improperly. Be careful to let any burnt material cool before touchin it or throwin it in the arbae.

2 Materials Balance Clay Butane safety lihter Graduated cylinder, 50-mL rin stand with clamp Pin, lare straiht Ruler, metric Biomass samples Soda can, empty and clean Glass stirrin rod watch lass water Ethanol Thermometer Procedure 1. Push a pin throuh the piece of clay so that the pin will be able to hold a piece of biomass and the clay will sit on the base of the rin stand. (See Fiure 1). Note: This setup will now be referred to as the Biomass Holder. *** 2. Place a biomass sample on the biomass holder. Measure the combined mass of the holder and sample. Record your data in the Data Table. Place biomass holder on the base of the rin stand. 3. Usin a raduated cylinder, measure and add 50.0 ml of water to an empty, clean soda can. 4. Bend the tab on the soda can and slide a lass stirrin rod throuh the hole. Suspend the can on a support stand usin a metal rin. Adjust the heiht of the can so that it is about 2.5 cm above the biomass holder. 5. Insert a thermometer into the can. Measure and record the initial temperature of the water. 6. Rotate the can so it is not directly above the sample. Liht the biomass sample. (It may take time for the sample to bein burnin and you don t want the flame of the lihter to heat the water in the can.) Fiure 1 7. As soon as the sample beins to burn, place the can over the burnin biomass. Allow the water to be heated until the sample stops burnin. 8. As soon as the sample stops burnin, record the maximum (final) temperature of the water in the can. 9. Measure and record the final mass of the holder and sample. 10. Remove any biomass residue from the food holder. 11. Repeat steps 1 10 for a total of 3 veetative biomass samples and 3 food biomass samples. ***You will need to construct an alternative holder for samples that will not stick on the end of the pin. In order to do this, fold a small aluminum boat from a piece of foil and place your sample in the aluminum boat. Place this on the base of the rin stand. Don t foret to lower the aluminum can so it is as close to the burnin sample as when you use the pin holder set up. 12. The combustion of ethanol as fuel Record the mass of an empty watch lass. Place 15 drops of ethanol (C 2 H 5 OH or CH 3 CH 2 OH) onto a watch lass and re-mass it. Place the watch lass under the tin can calorimeter. Liht a wooden splint and place it near the ethanol. Allow the ethanol to burn and record the temperature chanes.

3 BIOMASS CALORIMETER LAB Names:,,, Data Table Biomass Sample Initial Mass (sample and holder) Final Mass (sample and holder) Chane in mass Initial Temp. 0 C Final Temp. 0 C Δtemp. Ethanol sample Analysis and Calculations (you will need to compute some of these on a separate sheet of paper) 1. For each sample burned, determine the chane in temperature of the water by subtractin the initial water temperature from the final water temperature. 2. Calculate the heat ained by the water usin Equation 1 from the Backround section: Q = m x C x ΔT. The mass of water used is 50.0 and the specific heat of water (C) is 1.0 cal/ C. These values will ive you the heat ained in calories. Biomass sample 1: Biomass Sample 2: Biomass Sample 3: Biomass sample 4: Biomass Sample 5: Biomass Sample 6: 3. Convert the heat ained from calories to food Calories (kilocalories) by dividin the answers above by Then convert to BTU s (1 Btu = 252 cal) Sample 1: cal = Cal. Sample 2: cal = Cal. Sample 3: cal = Cal. Sample 4: cal = Cal. Sample 5: cal = Cal. Sample 6: cal = Cal.

4 4. Determine how much of the biomass burned by subtractin the final mass of the assembly from the initial mass. (note: you may not be able to complete this calculation if the mass loss from burnin was not measurable) 5. Calculate the enery content per ram of the biomass sample. This is done by dividin the heat ain of the water (in Calories), by the chane in mass of the sample. (see note for #4 above) Sample 1: cal (Δmass) = Enery/ram. Sample 2: cal (Δmass) = Enery/ram. Sample 3: cal (Δmass) = Enery/ram. Sample 4: cal (Δmass) = Enery/ram. Sample 5: cal (Δmass) = Enery/ram. Sample 6: cal (Δmass) = Enery/ram. 6. Review how the amount of enery released differs amon the biomass samples. What do you think is an explanation for these differences? 7. If you were hired to develop a new fuel source for enery, and assumin any of the samples you tested were viable candidates, which one would you choose? Justify your answer usin your experiment results. 8. What are the potential advantaes and disadvantaes of extractin enery from biomass materials throuh combustion?

5 7. Sam Snackalday wanted to calculate the enery per ram of food from some of his favorite snack foods. He recorded the data below. Follow the same steps as you did for your own data (#1-5 above) and calculate the enery content per ram of Sam s snack food, then rank the food samples from reatest (1) to least (3) in terms of enery per ram of food. enery per rankin Food Sample Initial Mass (food and holder) Final Mass (food and holder) Initial Temp. of Water 0 C Final Temperature 0 C Cheese puff C 27.1 C Marshmallow C 23.6 C Onion rin C 30.1 C