Project+-+Heat+of+Combustion+(P1)

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Introduction
It is often observed that chemical reactions result in a change in heat energy. Depending on the reactions, this heat energy is either absorbed or produced. Any reaction that absorbs heat is called endothermic, and any reaction that produces heat is called an exothermic reaction. It has been determined that if a reaction takes place within a closed, insulated container, then the heat absorbed or produced by the reaction will cause a distinct temperature change in the contents of the insulated container. This difference in heat energy of the reactants can be calculated and provides a quantitative measurement of the heat produced (or absorbed) in the chemical reaction. This experimental technique, the science of measuring heat, is called calorimetry. Any experiment in which heat is produced or absorbed and interacts with the environment (for example, the container) can be studied with calorimetry.

The calorific value of the fuel is the total amount of energy produced when 1 unit of mass of fuel undergoes complete combustion. For example, if 1 gram of fuel X is burnt and produces 50 kilojoules of energy, the calorific value of fuel X is therefore 50 kJ/g. The calorific value of fuels can be compared to determine which one is most efficient and can generate the greatest amount of energy. Also, properties of fuels can be compared and predicted based on their calorific values. In the experiment, the calorific values of the three fuels will be determined and can then be compared to show which of the three fuels has the greatest heat-generating capacity.

The experimental technique of calorimetry requires the use of a calorimeter, an instrument used to measure the heat of the reaction and thereby, any temperature changes during the course of the reaction. There are a variety of calorimeters, ranging from very large, sophisticated ones to simple designs that can be used in a school lab. The calorimeter must be a well-insulated container that can prevent any exchange of heat with the environment. Based on these specifications, even a Styrofoam cup can be successfully used in a school lab in place of a more expensive calorimeter. For this experiment we will use an aluminum calorimeter.

To calculate the calorific value of a fuel from the data given by the calorimeter, we will use the following equation: // Q = m   //   × //s// × //t// Where  //m//  = mass of water (g) //s//  = specific heat  of the water (4.2 J / g  ° C   ) //t//  = rise in temperature of the water //Q // = the amount of heat energy that is generated by x grams of the fuel

Using the total amount of heat produced, the calorific value of the fuel can then be obtained: //Calorific value// = //Q// J /// x//  g Where //x// = the weight of the fuel (grams)

The purpose of the experiment is to ascertain how the efficiency of a fuel can be measured and compared against other fuels using solely the experimental technique of calorimetry in determining the calorific value of that fuel.

Materials

 * Paraffin Wax
 * Cooking Oil
 * Butane
 * 50 g of Water
 * Graduated Cylinder
 * Calorimeter
 * Thermometer
 * Scale
 * Safety Goggles

Procedure

 * 1) 50 g of water was poured into the calorimeter.
 * 2) The temperature of the water was measured and recorded.
 * 3) Paraffin wax was obtained, measured, and placed into the calorimeter.
 * 4) The paraffin wax was ignited and allowed to burn for at least 2 minutes, or until the flame went out.
 * 5) The temperature of the water was measured again and recorded.
 * 6) The paraffin wax was disposed of and the calorimeter's compartments were cleaned thoroughly.
 * 7) The water was disposed of and replaced.
 * 8) Steps 2 through 7 were repeated for cooking oil and butane.
 * 9) The work area was cleaned and all equipment replaced.

Safety
Safety goggles and appropriate protective clothing were worn, and all long hair was tied back. The experiment area was cleared of all unneeded equipment and flammable material. When the experiment was performed, an adult was present. Fire exits and procedures were known to all participants. Butane was handled with particular care, as it is very flammable as well as poisonous if inhaled. After the experiment was performed, the experiment area was cleared and all refuse was disposed of accordingly.

Observations
The following observations were made during the experiment:

Data Table
  of water (°C)** ||= **Final Temperature of water (°C)** ||= **Initial Mass of Fuel* (g)** ||= **Final Mass of Fuel* (g)** ||= **ΔMass(g)** ||= **ΔTime (s)** ||
 * = **Fuel** ||= **Initial Temperature
 * < Paraffin Wax ||= 22.5 ||= 25.6 ||= 16.963 ||= 16.877 || 0.086 ||= 134 ||
 * < Cooking Oil ||= 22.5 ||= 25 ||= 9.575 ||= 9.534 || 0.041 ||= 40 ||
 * < Butane ||= 22 ||= 39 ||= 210.443 ||= 210.170 || 0.273 ||= 120 ||
 * Includes container

Calculations
The following calculations were required to complete the experiment:

**Paraffin Wax**: = (initial mass) – (final mass) = 16.963g – 16.877g = 0.086g Therefore, 0.086g of paraffin wax was burned during the experiment.

**Cooking Oil**: = (initial mass) – (final mass) = 9.575g – 9.534g = 0.041g Therefore, 0.041g of cooking oil was burned during the experiment.

= (initial mass) – (final mass) = 210.443g – 210.170g = 0.273g Therefore, 0.273g of butane was burned during the experiment.
 * Butane**:

**Paraffin Wax**: = (final temperature) – (initial temperature) = 25.6°C – 22.5°C = 3.1°C Therefore, the temperature of the water increased 3.1 °C with paraffin wax.

**Cooking Oil**: = (final temperature) – (initial temperature) = 25°C – 22.5°C = 2.5°C Therefore, the temperature of the water increased 2.5°C with cooking oil.

= (final temperature) – (initial temperature) = 39°C – 22°C = 17°C Therefore, the temperature of the water increased 17°C with butane.
 * Butane**:

**Paraffin Wax**: = (mass of water used) x (specific heat capacity of water) x (difference in temperature) = 50g x 4.18 J/°Cg x 3.1°C = 647.9 J Therefore, 647.9 joules of energy were produced by combustion of paraffin wax.

= (mass of water used) x (specific heat capacity of water) x (difference in temperature) = 50g x 4.18 J/°Cg x 2.5°C = 522.5 J Therefore, 522.5 joules of energy were produced by combustion of cooking oil.
 * Cooking Oil**:

= (mass of water used) x (specific heat capacity of water) x (difference in temperature) = 50g x 4.18 J/°Cg x 17°C = 3553 J Therefore, 3553 joules of energy were produced by combustion of butane.
 * Butane**:

PART 4: __Calculating Calorific Value__
**Paraffin Wax**: = (heat produced) / (mass of fuel burned) = 647.9 J / 0.086g = 7533.72 J/g = 7.53 kJ/g = 1800.60 cal = 1.80 kcal Therefore, the calorific value of paraffin wax is 7.53 kilojoules or 1.8 kilocalories per gram.

= (heat produced) / (mass of fuel burned) = 522.5 J / 0.041g = 12743.90 J/g = 12.74 kJ/g = 3045.87 cal = 3.05 kcal Therefore, the calorific value of cooking oil is 12.74 kilojoules or 3.05 kilocalories per gram.
 * Cooking Oil**:

= (heat produced) / (mass of fuel burned) = 3553 J / 0.273g = 13014.65 J/g = 13.01 kJ/g = 3110.58 cal = 3.11 kcal Therefore, the calorific value of butane is 13.01 kilojoules or 3.11 kilocalories per gram. **Calorific Values**: Parrafin Wax: 7.53 kJ/g Cooking Oil: 12.74 kJ/g Butane: 13.01 kJ/g
 * Butane**:

PART 5: __Calculating Molar Calorific Value__
**Paraffin Wax**: = (heat produced) / (number of moles of fuel burned) = (heat produced) x (mass of fuel burned) / (molar mass of fuel) = 647.9 J x 0.086g / 352.688g/mol = 0.158 J/mol = 0.038 cal/mol Therefore, the calorific value of paraffin wax is 0.158 joules per mole, or 0.038 calories per mole.

= (heat produced) / (number of moles of fuel burned) = (heat produced) x (mass of fuel burned) / (molar mass of fuel) = 522.5 J x 0.041g / 282.52g/mol = 0.076 J/mol = 0.018 cal/mol Therefore, the calorific value of paraffin wax is 0.076 joules per mole, or 0.018 calories per mole. = (heat produced) / (number of moles of fuel burned) = (heat produced) x (mass of fuel burned) / (molar mass of fuel) = 3553 J x 0.273g / 58.12g/mol = 16.689 J/mol = 3.993 cal/mol Therefore, the calorific value of paraffin wax is 16.689 joules per mole, or 3.993 calories per mole.
 * Cooking Oil**:
 * Butane**:

**Molar Calorific Values**: Paraffin Wax: 0.158 J/mol Cooking Oil: 0.076 J/mol Butane: 16.689 J/mol

PART 6: __Percentage Error__
According to the results, butane was the most efficient of the three fuels, producing 13.01 kilojoules per gram of energy when ignited and burned. After further research, it was found that the real calorific values of paraffin, cooking oil, and butane are 46 kJ/g, 35 kJ/g, and 49.5 kJ/g respectively. This confirmed the general pattern of the results, but showed that the values that were obtained were incredibly inaccurate.

The percentage error of experimental data is calculated with the following formula: //% Error = |(Theoretical Value - Experimental Value) / Theoretical Value//|   ×    <span style="font-family: 'Times New Roman',Times,serif;"> //100%//

**Paraffin Wax**: % Error = |(46 - 7.53) / 46| x 100% = 83.63%

% Error = |(35 - 12.74) / 35| x 100% = 63.6%
 * Cooking Oil**:

% Error = |(49.5 - 13.01) / 49.5| x 100% = 73.7%
 * Butane**:

Due to the many sources of error which could not have been eliminated, the experimental data collected were greatly inaccurate.

Conclusion
This experiment was done to try to determine the calorific value of 3 different fuels by using the techniques of calorimetry. The fuels were burned inside a calorimeter, and the resulting changes in the mass of the fuels and the temperature in the calorimeter were used to calculate the calorific values of the fuels. It was concluded that calorimetry techniques can be used to measure and compare the combustion efficiency of a fuel against other fuels. Out of the 3 fuels that were tested in the experiment, butane released the most heat during combustion and therefore, is the most effective fuel.

Discussion
There are many ways to apply the technique of calorimetry in the real world. Oil companies, for example, are always looking for better gasolines, and so the techniques of calorimetry can be used to compare and measure the efficiency of fuels and to help find better and more efficient fuels. By using the technique of calorimetry to experiment on different types of gasoline, one can test potential new fuels and compare their efficiency to current fuels.

The technique of calorimetry is also used to help people understand their diet and their energy intake. The number of calories of a certain food can be found on most nutrition labels. These numbers were most likely found using a calorimeter, since calorimetry and the process of respiration and energy consumption in the human body are quite alike. Once food is consumed by a person, the food is "burnt" inside the person's body through the process of respiration. This process results in the release of energy. This is quite similar to the combustion of a fuel with oxygen so the number of calories is really just the calorific value of the food per serving size.

Sources of Error
As with any experiment, error is inevitable. Although care was taken to avoid as much human error as possible, some errors are unavoidable. One of the biggest sources of error was the loss of heat from the calorimeter during the experiment. There were several ways this occurred. Both the school calorimeter and the home-made equivalent had very little insulation, which allowed heat to be lost through the sides. Heat was lost through ventilation, as the calorimeter had to be opened to let in oxygen for the fire. The homemade calorimeter also wasn’t large enough for the butane lamp and thus there was a large gap at the bottom for heat to escape. Furthermore, heat was lost when the fuel had to be ignited outside of the calorimeter then quickly placed inside it. Since the change in temperature is essential for calculating calorific value, the loss of heat could have resulted in the large percentage error.

Another possible source of error was the weighing of the fuels. The scale that was used was accurate to three decimal points, but the last decimal place often fluctuated. Although it was only between 0.001g to 0.005g, the change in mass was usually only around 0.05g. Therefore the scale may have made ~10% difference.

The heat of combustion is defined as the energy released as heat when one unit of a compound undergoes complete combustion with oxygen. The lack of oxygen inside the calorimeter could have resulted in the incomplete combustion of the fuels, leading to incorrect data. Finally, to properly measure the heat of combustion, a bomb calorimeter is required. In addition to this, instruments to measure the temperature change in each component of the bomb calorimeter must also be present. A metal can cannot possible be as effective or as accurate as a bomb calorimeter. Thus an idea of the results could be obtained, but accurate results in our case could not.

Suggestions for Modifications
Before the experiment was started, it was realized that the original experiment had some flaws. It was intended that sugar be one of the fuels, but in trial runs there were difficulties in getting it to burn. It was found that the sugar would only burn once it had melted, making it inconvenient to use as a fuel. Therefore the butane lamp was proposed as a replacement. However, it too had its problems. It was too large to fit inside the school calorimeter, and a new calorimeter had to be made. This was accomplished by using a lidless empty coffee can with cardboard sides and a metal bottom. It was turned upside down and a hole was cut in the bottom for the water container. The inside was covered in metal tape to prevent fire. Unfortunately, it was just too small for the butane lamp. During the experiment, the calorimeter had to be tilted sideways in order to fit the butane lamp through the bottom. This left a huge gap and was one of the sources of error for the experiment.

Ideally, for this experiment, a bomb calorimeter would be used. However, this is not very practical since they are very expensive. Therefore, there are several ways that the current calorimeter could be improved to prevent further heat loss. The new design should include better insulation and ventilation holes near the bottom. Although ventilation causes heat loss, it is necessary to keep the fuel burning. The alternative would be to burn the fuel with only the oxygen already in the calorimeter, but that would require the measurements of temperature and mass to be extremely accurate. The advantage of having ventilation holes near the bottom is the reduction of heat loss through convection. Since hot air rises, less heat would be lost than if the holes were near the top. Also, CO2 is heavier than O2 and would sink to the bottom, to be replaced by oxygen from the ventilation holes. The new design should have a door in the bottom, so that the fuel could be inserted beforehand and then lit through the door to minimize heat loss. A digital thermometer with decimal places would help in taking more accurate readings of temperature.