Comparing the Energy Content of Biofuels 11/14

Integrated Science 3 Name: Per:

Introduction

You have identified a number of different energy sources that are important to humans – including those used now and those used more extensively in the past. These different sources have very different energy content values. The energy content of a substance is the amount of heat produced or given off by the combustion of one gram of that substance. The energy content, in turn, is critical in how a specific source can be used. For example, burning one gram of wood yields approximately 2,760 calories of heat, while coal can produce 7,200 calories per gram. With its greater energy content, coal was able to more efficiently provide the vast amounts of heat needed for the factories of the Industrial Revolution. Today there is increasing interest in Biofuels as a fuel source. Ethanol is a renewable fuel used to power vehicles and other internal combustion engines. Ethanol is currently made from feedstock crops such as corn, barley and sugarcane that contain significant amounts of sugar, or materials that can be converted into sugar, such as starch. Ethanol is produced when bacteria and/or yeast ferment grain products. Ethanol is often used as a fuel additive to produce a more efficient, cleaner and cooler-burning fuel. Another biofuel is biodiesel. Biodiesel is a renewable, clean-burning diesel replacement that is made from a diverse mix of feedstocks including recycled cooking oil, soybean oil, and animal fats. It can be used in existing diesel engines without modification. In this lab, you will determine and compare the heat content of these biofuels and compare them to other known fuel sources.

Procedures

As a class, we will be collecting multiple trials to determine the energy content of biofuels in order to test efficiency of the energy that is produced. Your lab group will be responsible for completing both of the procedures for Part 1. Determining the Energy Content of Ethanol and Part 2. Determining the Energy Content of Biodiesel. Each lab group is responsible for completing Part 3. Determining the Energy Content of Kerosene and Part 4. Comparing the Energy Content of Various Fuel Sources.

Laboratory Notebook: Create a laboratory notebook for this experiment. Record observations about each type of fuel you test.

Ø  Part 1. Determining the Energy Content of Ethanol

1.  Using an electronic balance, determine and record the initial mass of the burner and fuel in Data Table 1. Make all mass measurements to the nearest 0.1gram.

2.  Using a graduated cylinder, measure exactly 125 ml of cold water and add it to the beaker. Use the density of water to determine and record it’s mass in grams in Data Table 1.

3.  [Density of water = 1.0g/cm3 = 1.0g/ml]

4.  Set up the calorimeter as demonstrated by your teacher. Make adjustments so that the flame from the burner (do not light it yet) will just touch the bottom of the beaker.

5.  Record the initial temperature of the water to the nearest 0.5 ºC in Data Table 1.

6.  Light the wick and heat the water until the temperature reaches between 55 and 60 ºC. Stir the water while it is heating. Record final temperature on your data sheet in Data Table 1.

7.  Blow out the flame. Determine and record the final mass of the burner and fuel in Data Table 1.

8.  Use your data and the equations provided to calculate the energy content of ethanol. Record these calculated values in Data Table 2.

Ø  Part 2. Determining the Energy Content of Biodiesel

1.  Using an electronic balance, determine and record the initial mass of the burner and fuel in Data Table 3. Make all mass measurements to the nearest 0.1gram.

2.  Using a graduated cylinder, measure exactly 125 ml of cold water and add it to the beaker. Use the density of water to determine and record it’s mass in grams in Data Table 3.

3.  Set up the calorimeter as demonstrated by your teacher. Make adjustments so that the flame from the burner (do not light it yet) will just touch the bottom of the beaker.

4.  Record the initial temperature of the water to the nearest 0.5 ºC in Data Table 3.

5.  Light the wick and heat the water until the temperature reaches between 55 and 60 ºC. Stir the water while it is heating. Record final temperature on your data sheet in Data Table 3.

6.  Blow out the flame. Determine and record the final mass of the burner and fuel in Data Table 3.

7.  Use your data and the equations provided to calculate the energy content of ethanol. Record these calculated values in Data Table 4.

Ø  Part 3. Determining the Energy Content of Kerosene (for comparison)

1.  Use the data and equations provided in Data Table 5. to calculate the energy content of Kerosene. Record these calculated values in Data Table 6.

Ø  Part 4. Comparing the Energy Content of Various Fuels

1.  Complete Data Table 2 by recording the data collected by lab groups that determined energy content of ethanol, and calculating the mean values for energy absorbed, energy released and efficiency for the class data.

2.  Complete Data Table 4. by recording the data collected by lab groups that determined the energy content of biodiesel, and calculating the mean values for energy absorbed, energy released and efficiency for the class data.

3.  Complete Data Table 7. by recording the values for mean energy content and mean efficiency of the fuel source.

Calculations:

1. Calculate the heart energy absorbed by the water. Use the equation below:

The specific heat of water is 1 calorie/gram °C.

2. Calculate the energy content per gram of ethanol. Use the equation below.

3. Calculate the percent error, comparing your results for energy content with the actual results (in Data Table 8. of the Analysis and Conclusion section). Use the equation below.

Data

Data Table 1. Raw Data – Energy Content of Ethanol

Your group’s Raw Data
Initial mass of ethanol(g)
Final mass of ethanol (g)
Mass of ethanol burned (g)
Mass of water (g)
Initial temp. of water (ºC)
Final temp. of water (ºC)
Temp. change of water (ºC)
/ Data Table 2. Raw Data – Energy Content of Biodiesel
Your group’s Raw Data
Initial mass of biodiesel(g)
Final mass of biodiesel(g)
Mass of biodiesel burned(g)
Mass of water (g)
Initial temp. of water (ºC)
Final temp. of water (ºC)
Temp. change of water (ºC)

Data Table 1. Raw Data – Energy Content of Ethanol

Your group’s Raw Data
Initial mass of ethanol(g)
Final mass of ethanol (g)
Mass of ethanol burned (g)
Mass of water (g)
Initial temp. of water (ºC)
Final temp. of water (ºC)
Temp. change of water (ºC)

Data Table 4. Calculations – Energy Content of Biodiesel

Trial #1 / Trial #2 / Trial #3 / Trial #4 / Trial #5
Heat energy absorbed (cal)
Energy content (cal/g)
Efficiency (%)

Data Table 4. Calculations – Energy Content of Biodiesel

Trial #6 / Trial #7 / Trial #8 / Trial #9 / Trial #10 / Mean Value
Heat energy absorbed (cal)
Energy content (cal/g)
Efficiency (%)

Data Table 5. Raw Data – Energy Content of Kerosene

Initial mass of kerosene(g) / 192.8
Final mass of kerosene(g) / 191.4
Mass of kerosene burned (g) / 1.4
Mass of water (g) / 125
Initial temp. of water (ºC) / 27
Final temp. of water (ºC) / 56
Temp. change of water (ºC) / 29

Data Table 6. Calculations – Energy Content of Kerosene

Heat energy absorbed (cal)
Energy content (cal/g)
Efficiency (%)

Data Table 7. Summary Data

Energy Source / Mean Energy Content (cal/g) / Mean Efficiency (%)
Ethanol
Biodiesel
Kerosene

Graph: Graph the data from Data Table 7. (Summary Data)

Analysis and Conclusions

1.  Use Data Table 7. to compare the efficiency values for each fuel source tested. What contributed to the efficiency of burning each type of fuel tested?

2.  Use Data Table 8. to compare the actual energy content values for the ethanol and biodiesel with the values of other known energy sources. Given the actual energy content, what might be appropriate uses for each type of fuel?

3.  What are the drawbacks of using ethanol as an energy resource? Biodiesel?

4.  Identify the tested fuel as renewable, potentially renewable or non-renewable energy sources.

5.  Uranium-235 has, by far, the largest energy content value of the fuels compared in Data Table 8. Would you recommend its use as a primary energy source for human energy needs? Why or why not?

Data Table 8. Actual Energy Content Values of Known Fuels

Item

/ Energy Content (cal/g)
Beef steak / 1,840
Alcohol (Scotch, 80 proof) / 2,580
Bread / 2,660
Wood / 2,760
Sugar / 4,100
Ethanol / 6,400
Coal (stove coal) / 7,200
Biodiesel / 7,950
Fuel oil (kerosene) / 10,800
Natural gas / 11,000
Paraffin wax / 11,250
Gasoline / 11,530
Uranium-235 / 20,000,000

Further Study:

Research and explain the production of the fuel type you tested (ethanol or biodiesel).