Planning - The aim of the experiment is to work out the enthalpy change of combustion of a fuel.

This shows an endothermic reaction because the products are at a higher energy level than the reactants. The difference in height shows the energy taken in during the reaction.

A combustion reaction is an oxidation reaction in which heat is given out. If there is heat, the combustion is described as burning. Substances that undergo combustion are called fuels. Alcohols are fuels.

Alcohols are a class of chemical compounds, all of which consist of chemically bonded atoms of carbon, hydrogen, and oxygen. All alcohol molecules contain at least one hydroxyl group. A hydroxyl group is a specific arrangement of atoms in which a hydrogen atom is bonded to an oxygen atom. In alcohol molecules, the oxygen atom in the hydroxyl group is, in turn, bonded to a carbon atom.

A hydroxyl group:

They have the general formula: CnH2n+1OH

The structures of the 5 alcohols I will be experimenting with:

Methanol:

Ethanol:

Propanol:

Butanol:

Pentanol:

SECONDARY SOURCES

Chemistry for GCSE - E.N. Ramsden

CGP Chemistry Revision Guide - Richard Parsons

Class notes

http://www.bbc.co.uk/education/gcsebitesize/

http://www.revise.it/

PRELIMINARY WORK

The loss in mass of methane was measured, after heating 50cm³ of water until it went up by 20°C. It was found that the temperature rises by 20°C very quickly, meaning that the results would be less accurate as there is a smaller degree of error. Therefore I decided to measure a temperature rise of 30°C instead. I thought that using 50cm³ of water would be fine.

EXPERIMENTAL PREDICTION

I predict that the more bonds there are holding the carbon, oxygen and hydrogen atoms together; more energy will be required to break them apart. Therefore, the more carbon bonds there are, the greater the enthalpy change of the fuel.

The number of carbon atoms is proportional to the enthalpy change of the fuel

FACTORS TO VARY AND CONTROL AND RANGE OF OBSERVATIONS

Factors to remain constant:

Mass of water - 50g / 50cm³

Temperature change - 30°C

Factors to vary:

The alcohols used - Methanol, ethanol, propanol, butanol, pentanol

Factor to measure:

Mass change in the alcohol

PROCEDURE

Apparatus List:

* Spirit burners with alcohol in them

* Copper beaker

* Retort stand with 2 clamps

* Heat-proof mat

* Measuring cylinder

* Electronic weighing scales

* Thermometer

Method:

Firstly 50cm³ of water was measured into a copper beaker. The beaker was then placed into the grasp of the clamp stand. A thermometer was then clamped above it. The starting temperature of the water was measured. The spirit burner was then weighed on an electronic weighing scale with the lid on. Then, the spirit burner was placed 15cm under the copper beaker. The thermometer was then inspected until the temperature of the water had risen exactly 30ºC above the starting temperature. The spirit burner was then weighed, and the change in mass was noted down.

Accuracy:

* Make sure you read the thermometer at eye level.

* Make sure that the size of the wick is roughly the same size in each experiment.

Safety:

* Make sure that the wick of the spirit burner does not fall into the alcohol while it is on fire, as it will cause an explosion.

* Make sure that you wash your hands if you come into contact with any of the alcohols, as most of them are toxic.

* Make sure that the thermometer and the copper tin is firmly clasped into the clamp-stand, as it could cause damage to the thermometer, or injury to you if one of them falls off.