Original post by 2F0L0Y2
What does it mean when the percentage error of the practical heat of combustion (energy released) is larger than the percentage error of the mass of water, change in fuel and change in temperature added together?
What other sources of error are there?
(what is the single largest source of error?)
Is this what you mean by the sources of error?
Experiment was conducted on different days (weather was really different on each day. first day was sunny and hot while the second day had rain and was a bit colder)
The foil we used to cover the experiment changed each time because it either got ripped or we had to use more foil.
The length of time each fuel had to burn.
Some of the trials had soot at the bottom of the flask
In some of the trials the flask wasn't cooled down properly making the initial temperature higher than it should have been.
Experiment was conducted on different days (weather was really different on each day. first day was sunny and hot while the second day had rain and was a bit colder)
The foil we used to cover the experiment changed each time because it either got ripped or we had to use more foil.
The length of time each fuel had to burn.
Some of the trials had soot at the bottom of the flask
In some of the trials the flask wasn't cooled down properly making the initial temperature higher than it should have been.
Original post by Pigster
What other sources of error are there?
(what is the single largest source of error?)
(what is the single largest source of error?)
They certainly seem like things that may affect the measured change in T.
Some will have bigger effects than others, some might (in theory) even have no effect.
None of them are an outright statement pointing out what the largest source of error is, i.e. what one thing will lead to your measured change in T being different to the theoretical value for change in T.
Some will have bigger effects than others, some might (in theory) even have no effect.
None of them are an outright statement pointing out what the largest source of error is, i.e. what one thing will lead to your measured change in T being different to the theoretical value for change in T.
Original post by 2F0L0Y2
Is this what you mean by the sources of error?
Experiment was conducted on different days (weather was really different on each day. first day was sunny and hot while the second day had rain and was a bit colder)
The foil we used to cover the experiment changed each time because it either got ripped or we had to use more foil.
The length of time each fuel had to burn.
Some of the trials had soot at the bottom of the flask
In some of the trials the flask wasn't cooled down properly making the initial temperature higher than it should have been.
Experiment was conducted on different days (weather was really different on each day. first day was sunny and hot while the second day had rain and was a bit colder)
The foil we used to cover the experiment changed each time because it either got ripped or we had to use more foil.
The length of time each fuel had to burn.
Some of the trials had soot at the bottom of the flask
In some of the trials the flask wasn't cooled down properly making the initial temperature higher than it should have been.
The enthalpy change of combustion has a unit of kJ/mol and its formula = mc(delta T)/ no. of moles of fuel, where m represents mass of water, c represents specific heat capacity of water and delta T represents change in temperature. No. of moles of fuel can be calculated by dividing its mass over its relative molecular mass, assuming you know the identity of the fuel. In most calorimetry experiments, it is assumed that there is negligible heat loss. However, that is very hard to achieve in practical experiments. Most of the errors for mass of water and temperature change comes from the accuracy of the instruments, and it is very straightforward to resolve those issues. For example, if the temperature rise is 5 degree celsius and the thermometer used has a division of 1 degree celsius, then the temperature measured may not be accurate. To solve this problem, we just use a thermometer with greater precision. However, the main source of error or discrepancy between experimental enthalpy and theoretical enthalpy values comes from significant heat loss to the surrounding. The heat released from the combustion of fuel is not fully transferred to the water and raise its temperature. These error sources could be due to a) incomplete combustion of fuel, b) rapid loss of fuel due to evaporation especially immediately after the flame is extinguished, c) heat loss from flame due to draught and/or d) heat capacity of calorimeter was not taken into consideration etc. In other words, the percentage error of the practical combustion enthalpy is more like a summation of all the possible errors, including the percentage error of the mass of water and so on.
Hope it helps.
Hope it helps.
Original post by 2F0L0Y2
What does it mean when the percentage error of the practical heat of combustion (energy released) is larger than the percentage error of the mass of water, change in fuel and change in temperature added together?
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