Measuring heat energy of fuels

The combustion of alcohol is exothermic, and in this experiment, the energy released from burning a known mass of alcohol is used to heat a known amount of water. A comparison of various alcohols as fuels can be made by calculating the quantity of energy transferred to the water.

Required:

· Ethanol (HIGHLY FLAMMABLE) or Industrial Denatured Alcohol (IDA) (HIGHLY FLAMMABLE, HARMFUL)

· Propan-1-ol (HIGHLY FLAMMABLE, IRRITANT)

· Eye protection

· Balances (2 or 3 d.p.)

· Clamp, stand, and boss

· Hard glass test tube

· Spirit burner with a cap

· Stirring thermometer (0-110 °C)

· Glass rod

· Bunsen burner

Health & Safety

· Wear eye protection. Keep bottles of alcohol well away from flames.

· Ethanol, C2H5OH (l), (HIGHLY FLAMMABLE) and Industrial Denatured Alcohol (HIGHLY FLAMMABLE,

HARMFUL)

· Propan-1-ol, C3H7OH (l), (HIGHLY FLAMMABLE, IRRITANT)

Procedure:

1. Clamp the test tube at a suitable height to allow room for the spirit burner to be placed below. Allow a gap of around 2-5 cm between the base of the test tube and the top of the spirit burner. This gap may need to be adjusted depending on the height of the flame.

2. Using the measuring cylinder, fill the test tube can with 50 cm3 of water.

3. Using the thermometer, measure and record the initial temperature of the water.

4. Weigh the spirit burner (and cap) containing the alcohol and record the initial mass and name of the alcohol on a suitable table.

5. Place the spirit burner on the heat-resistant mat under the test tube, remove the cap, and light the wick.

6. Allow the alcohol to heat the water so the temperature rises by about 40°C. Use a glass rod or the thermometer to stir the water gently while the alcohol burns.

7. Replace the cap on the spirit burner to extinguish the flame.

8. Record the final temperature of the water using the thermometer. Work out the temperature change.

9. Reweigh the spirit burner and cap. Work out the mass of alcohol used.

10. Repeat the experiment for different alcohols using 50 cm3 of fresh cold water each time.

11. If time allows, repeat the experiment for each alcohol at least twice.

12. Using the formula q = mc∆T, calculate and compare the heat energy of different alcohols used as fuels.

STARTS: Lab report on comparing heat energy produced by combustion of various fuels of known mass

Hypothesis

When alcohols are combusted, it’s an exothermic reaction (giving off heat).

Replace the ‘water’ with an ‘automobile’ and ‘spirit lamp/burner’ with the diesel/petrol poured into automobiles. In exothermic chemical procedures, rapid reaction with oxygen, which is given by the source, called oxidizer, when an exothermic reaction between air and petrol causes releasement of energy, the car engine works.

(OR)

Replace the ‘fuel in spirit burner’, with the gas cylinder’s gas, the ‘lighter’ that we use to lit the fire on stove being the same used to lit the ‘spirit lamp/burner’, the ‘cooker’ kept on stove is ‘test tube with water’, ‘gas cylinder’ is the ‘spirit burner’, and the connection between ‘gas cylinder’ and ‘stove’, in this experiment, is the ‘distance between the test tube and the spirit burner’, all of which is how we make food and this is how both the practical circumstances here and above, can be put in place of the apparatus of this experiment that we can relate science to the real-world. ‘science is been discovered due to the real-world and the imagined-world’, meant the great works done by Mr. Albert Einstein and many other scientists, all of which created the subjectification/subject-content or material (study-material) of the educational institutions and systems, so It’s very important for a scientific learner to link ‘lab and home-life’ for connection between the real world and lab-world (la-world is part of imagined-world because there’s no use of all the scientific researchers if they cant be implemented in day-to-day lives.)

Transfer of heat energy occurs between 2 materials, caused by temperature. Combining oxygen or any other elements for the release of fire and heat. When alcohols are burnt, water and carbon dioxide are released, so at least there’s heat loss in the air due to combustion. There are three types of heat transfer are:

Conduction

Convection

Radiation

In this experiment, ‘Conduction’ is the type of heat transfer that’s involved because Conduction is the heat transfer between 2 directly contacted systems, where heat flows from the hot part/system to the cooler part/system instead of movement of the hot part/system IN cooler part/system. As the spirit burns/combusts alcohol, then without moving the spirit burner, its alcohol, the combusting alcohol will heat the COOL/ROOM TEMPERATURE water by releasing heat energy to the test tube, and hence the water. Energy’s amount released from the combusting alcohol to the room/cool temperature water amount increases with the number of bonds in the fuel because each bond has particular possession of an amount of energy; hence the more bonds, the more the energy storage and more released of energy from one substance to another when bonds break due to combustion.

After all of this, the result of this experiment will be hypothesized that ‘the higher the energy in kilojoules per mole, the more the benefit is, economically,’ which is the hypothetical rule determined to occur or not, based on the result of this experiment.

Presentation (Accurately use knowledge and understanding to recognize trends and draw conclusions from given data)

Name of the alcohol(used as a fuel)

1. Propan-1-ol

2. Ethanol

The initial temperature of the water is ‘0-degree celsius.’

1. 26.1

2. 26.2

The final temperature of the water is ‘0-degree celsius.’

1. 60.7

2. 60.7

Change of temperature in

‘0-degree celsius’

1. 60.7-26.1 = 34.6

2. 60.7-26.2=34.5

The initial mass of spirit burner’s alcohol that’s used as a fuel, in ‘g.’

1. 69.39

2. 67.8

The final mass of the spirit burner’s alcohol is fuel in ‘g.’

1. 60.6

2. 67.24

Mass of alcohol used up, meaning, in ‘g.’

1. 69.39-60.6 = 8.79

2. 67.8-67.24=0.59

Note that since the heat energy is transferred to the water in the test tube, then the final temperature of the water has to be increased and hence, to quantify the EFFECT (shown in terms of temperature increment in a test tube, after the reason is over)heat energy transferred from spirit burner to the water in a test tube, subtracting final-initial temperature has to be done, but this isn’t the same for the ‘mass of the alcohol’ because the final mass of the alcohol has to be decreased when it’s used up during the reaction, and hence to quantify the used-up group of alcohol, initial -(minus) final mass, has to be done.

Interpretation of the data: (implies for both alcohols, individually)

This is an exothermic reaction that gave off heat to the water in a test tube from the alcohol because, more evidently, in the experiment, the spirit burner’s alcoholic flame/fire caused the release of heat energy to the water in a test tube, as shows the Final temperature of the water in ‘0C’, which is higher than the Initial temperature of the water in ‘0C’ & inclusively, the mass of the alcohol used up during the reaction for transfer of heat energy to the water in a test tube, is shown in Final mass of spirit burner’s alcohol that’s used as a fuel, in ‘g’ which is lesser than Initial mass of spirit burner’s alcohol that’s used as a fuel, in ‘g.’

The exothermic reaction gives off heat, which is what happened from the spirit burner’s alcoholic flame to the water in the test tube but based on the aim of quantifying the heat energy transfer from the spirit burner to the water in the test tube, meaning, not just qualifying, instead also using q = mc∆T, for calculation/quantification and comparison of heat energy released, by different alcohols used as fuels, has to be ultimately worked out.

Qualifying the aim of this experiment, through the help of the data table above and now, further, leading to the answer for the entire goal of this experiment will be done…….

Aim of the experiment and this calculation: Did propan-1-ol or Ethanol provide the most heat energy per gram?

Calculation starts….

Propan-1-ol

∆H =q= mc∆T

=25*4.12*34.6=3563.8J

Hence, as IKJ=1000J,

Then for 3563.8J, we get 3.5638KJ.

As the number of moles of alcohol burnt=mass of alcohol by the molar mass of alcohol

Hence using the above rule, for propan-1-ol, we get:

8.79g by 60.09g/mol (where g in the numerator and g in the denominator will be canceled)= 0.146mol(3.d.p.)

Hence, calculating enthalpy change during combustion (∆H =q= mc∆T) by the number of moles of the alcohol, we get:

3.5638 KJ by 0.146 mol = 24.401KJ/mol(3.d.p.)

Exothermic reactions must have negative enthalpy change, the enthalpy change during combustion in KJ/mol for propan-1-ol is ‘-24.401KJ/mol.’

∆H =q= mc∆T = 25*4.12*34.5=3.5535KJ.

As the number of moles of alcohol burnt= mass of alcohol by the molar mass of the alcohol, then we get:

0.59g by 46.07g/mol = 0.013mol(3.d.p.)

∆H by alcohol’s number of moles = 3.5535KJ by 0.013 mol = 273.346 KJ/mol(3.d.p.)

Graph for the amount of energy released by each alcohol to the water in KJ/mol

As exothermic reactions must have negative enthalpy change, the enthalpy change during combustion in KJ/mol for Ethanol is ‘-273.346KJ/mol.’

By the calculation above and the hypothetical rule for the result of this chemical reaction specified in the hypothesis above, Ethanol produces a higher amount of energy in kilojoules per mole’.

Considering qualitative judgment/evaluation of the above significant calculation of enthalpy change during combustion in KJ/mol (international system of units) for both the alcohols experimented on:

For reference: ‘Burning’ is more of a scientific word, so unscientifically, ‘burning’ means ‘used-up.’

Just like in daily life, petrol/diesel is poured in automobiles, all of which is worked out for running the cars burning of alcohols is what we know, then in the same way, Also, In the lab premises, the entity of this lab experiment is that the exothermicity of ‘burning of alcohols’ is clearly seen through the transfer of heat energy from the burning of alcohols to the water in test tube, as showed by the increment in final temperature than initial temperature in ∆T (opposite of which is endothermic so qualitatively, this lab experiment is an exothermic reaction) and scientifically calculated (the calculation of enthalpy change during combustion in KJ/mol showed that the higher the energy, the higher the economic benefit (because when more energy is released during combustion, it means that the automobiles will work for more time when a lot of energy is released) and exothermicity becoming the property of this experiment and Ethanol had higher energy, becoming the best fuel to be used, than propan-1-ol for economic profit).

The daily-based exothermic exemplars of cooking food where gas cylinders burn chemical(s) in it so that they could provide heat to the stove and burning of fossil fuels, releasing heat energy, causes automobiles to run used by burning off those petrol/diesel, all of which mean that it’s imperative for a scientific learner to link ‘lab and home/daily life for connection between the real world and lab-world as there’s no use in using science in vastly complex areas if not used in micro-levels of scenarios.

This experiment comprises a type of heat transfer, namely ‘conduction’ (meaning, the heat transfer between 2 directly contacted systems, where the flow of heat from the hot part/system to the cooler part/system occurs, as we could observe in the experiment that:

· without moving the spirit burner, the test tube has water, or any other part of the laboratory equipment in this lab experiment, the alcohol burn, heated/transferred heat energy to COOL/ROOM TEMPERATURE water in a test tube, which is the procedure of conduction’.

· combustion causes the breaking of bonds, and so the amount of energy possessed by the alcohol is released to the other substance (like in this lab experiment’s case, the water in a test tube) so if there’s more bond energy in the alcohol, then more energy will be released to the other substance.

Hence the main hypothesis rule is provided, and the sub-hypotheses (every other information above, then the hypothetical rule) in the hypothesis, too.

Evaluation of method/procedure based on the outcome

Based on some research, this experiment is about measuring the heat energy of fuels and to KNOW the topic ‘fuels,’ and this is the basic and beginning experiment of exploring the topic ‘fuels. For us, the students, this experiment must be standard and approved to conduct on the lab premises. Hence, credibility lies at its peak while evaluating the method based on the outcome.

The outcome wasn’t contradicting what the method was leading to, and this method is the simplest as it’s within a 10th grader’s capability to do it.

The outcome could’ve gone wrong because the transfer of extreme heat will break the test tube, so while seeing the negative side of the evaluation of this method, based on the outcome, then the outcome could’ve been contradicting if the time needed for the experiment to go on, wouldn’t have been recorded. This is a negative side of the evaluation as this wasn't in the experiment.

· Distance between the test tube and the flame and the spirit burner. This factor is another applicable way to prevent heat loss. If this factor is varied for each trial or each alcohol, then the heat transfer’s accuracy will be varied (if there’s less distance, then there’d be a more accurate effect on the test tube, and if there’s more distance, then there’d be the less accurate effect on test tube).

· Reliability and credibility of the experiments had to be solved by TRIALS for each alcohol

· The huge error source is heat loss to the surroundings, which can be stopped by not closing the test tube, insulating the sides, and adding a lid. Example: surround the Bunsen burner/flame with tiles for decrement of heat’s area that could be lost/trapped so that its concentration on water increases.

· Initial temperature and volume/mass of water and spirit burner for any trials and alcohols have to be nearly constant/unvaried because our aim is to observe the temperature variance, (final-initial temperature) which is about how much heat energy transferred to water, meaning water’s final temperature, so how does absolute temperature affect the result of this experiment (higher the energy produced by alcohol, the more economically benefitting it is); purpose of this lab experiment will be deviated if initial temperature will be varied as effect of one object on the other can only be identified if all the other objects are kept constant, and in the same way, the mass/volume of the spirit burner and water are the other instantaneous factors, if these vary then the aim of studying the actual result of the experiment (meaning increment in final temperature of water, determining heat energy transferred to the water and then this increment will affect the enthalpy change during combustion so the absolute temperature can’t be changed.

Hence, the factors and their effects overlap with another element (S) rather than focusing on one factor's effect. Thus, the final temperature of the water, mass/volume of a spirit burner, and moisture don’t have to vary highly. Here comes the concept of independent variables (mass/volume and initial temperature of the water), like mass/volume of spirit burner and water and final temperature of the water, that will affect the dependent variables like the amount of heat energy transferred to the water/ enthalpy change during combustion. Hence, as explained above, initial temperature and mass/volume are other instantaneous factors. Therefore, mass/volume and initial temperature are independent variables that don’t have to vary for each trial of each alcohol highly, and the dependent variable is the amount of heat energy transfer to the water in KJ/mol (or) enthalpy change during combustion for each alcohol.