An investigation to determine which of four alcohols is the most exothermic :: GCSE Chemistry Coursework Investigation

An investigation to determine which of four alcohols is the most exothermic Prediction I predict that the most heat given out per mole burned would be by Propanol because the size of the alcohol molecules might increase with heat. Alcohols produce heat when they burn in oxygen or air. The amount of heat produced per mole of alcohol will be proportional to the amount of air present. Full combustion should generate two products only: carbon dioxide and water vapour. Hypothesis Within a molecule there are bond energies that are holding the atoms together. When the fuel combusts a chemical reaction takes place, this breaks the bonds, this requires energy, and makes new bonds this gives out energy. The energy differences between the two tell us how much energy was given out or taken in. We can show this on a graph. Alcohol particles will break their bonds when they mix with oxygen. This is known as exothermic reaction. Boiling points will be increased because energy is needed bonds can be formed and broken. Breaking bonds need less energy than is needed to form bonds - exothermic reaction. Bigger molecules use high energy to be broken. Methanol and Ethanol have differences as Methanol melts at a higher temperature and boils at a lower temperature than Ethanol. Higher alcohols which include Butanol and Propanol have a higher molecular weight and this is why Butanol is used in perfumes. Ethanol, which is sugar based, with its low freezing point, has a specific use as antifreeze for cars and other vehicles. GRAPH Tripod Matches Goggles Method: - To begin with, I choose one out of the four different alcohols. I weigh beforehand in the spirit burner. This is so I can calculate the mass which is lost in each alcohol. The spirit burner and alcohol which I am using is on a brick under a tripod. On the tripod I place a clay pipe triangle which holds a beaker containing 100ml of water. I light the spirit burner and stir the water with the thermometer constantly. When the temperature has risen to 30Â ºC, I quickly place the top back on the spirit burner. Now I re-weigh the alcohol. o find out how much alcohol has been burned I subtract the finishing mass from the starting mass. Fair Test I will try my best to keep this experiment fair. All the variables must be controlled. These are as follows - The scale reading has to be on zero before weighing the spirit burner