Essay About Heat Combustion Of An Alcohol And Relative Molecular Mass Changes

Investigating How the Relative Molecular Mass Changes in Heat Combustion of an Alcohol:
Essay title: Investigating How the Relative Molecular Mass Changes in Heat Combustion of an Alcohol:
Investigating How the Relative Molecular Mass Changes in Heat Combustion of an Alcohol
Planning
Introduction
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As alcohol burns in air it gives out energy as heat and light. I am
going to investigate how the energy output of an alcohol in combustion
changes, with increased relative molecular mass, or RMM. RMM is the
sum of the atomic masses of every atom in the molecule. Using the
alcohols: Methanol, Ethanol, Propan-1-ol, Butan-1-ol and Pentan-1-ol,
I will plan, and complete an experiment that tests the prediction
below.
Prediction And Theory
In the combustion of alcohols in air, the alcohol reacts with oxygen
molecules, to create carbon dioxide and water. Many bonds are broken
in the process using up energy. At the same time, the atoms reforming
into the new molecules of carbon dioxide and water give out energy. In
the combustion of alcohols, the energy created, when forming bonds
will always be more that what is lost, when breaking bonds, this gives
us excess energy. This energy is given out primarily as heat, but also
as light and sound. As energy is given out it is called an exothermic
reaction. If the opposite were true, it would be an endothermic
reaction. It is never possible to calculate exact energy change by
experimentation due to inaccuracies and energy waste, so we use bond
energy calculations give the exact theoretical energy change.
Bond energy calculations show that the higher the RMM the more energy
will be produced for the same weight of fuel (RMM is the sum of the
atomic masses of every atom in the molecule). This is because as the
RMM increases there are more atoms and therefore, more bonds to be
broken and then made. As, when burning alcohols, this process gives
out energy, the more bonds go through this process, ie as the RMM
increases the more energy should be released. The calculations also
suggest that for every carbon atom you add to the chain of an alcohol
the energy out should increase by
618 Kj/mol. I predict then, that as the RMM goes up then the energy
change will get increasingly more negative i.e. more energy is given
off. The RMM will be proportional to the final energy created as both
should increase by the same number each time, (RMM by 14 as one C and
2 H atoms are added, and the energy out by 618KJ/mol). This will
therefore result in a straight-line on the graph. The bond energy
calculations show how much energy should be released, accounting for
experimental inaccuracies however, I expect the experimental output to
be considerably less.
Proposed Method
I am going to test how the energy output per mole in the combustion of
alcohols with increasing RMM. I need, therefore, to be able to measure
the energy given out in combustion and then divide that by the amount
of moles used. As the majority of energy given out is in the form of
heat energy, I will attempt to measure the heat energy