The link between the number of carbon atoms in a fuel with the amount of energy it releases
Alcohols generally belong to compounds whose molecules are based on chains of carbon atoms. They usually contain one oxygen atom, which is joined to a carbon atom by a singular bond. This makes them different to other compounds. The oxygen atom is joined to the hydrogen atom as well as the carbon atom, which makes the oxygen a part of a hydroxyl group. These atoms are generally a part of a hydrocarbon chain. These alcohols can take away water from the body, in which a hydrocarbon chain has replaced a hydrogen atom. Alcohols have a general structure of CnH2n+1OH
The aim of this investigation is to see the link between the numbers of carbon atom in a fuel with the amount of energy it releases. There would be a change in the amount of energy given off that is getting greater, the more carbon atoms in the fuel, the more there are more bonds to be broken and formed, thus producing more energy. ‘In a chemical reaction, bonds in the reactant molecule are broken and new ones are formed. Atoms are rearranged. Energy has to be put in to break bonds, and energy is given out when bonds are formed.’ When the total energy put in is greater than the energy put out, the substance cools down (it is endothermic). This is expressed as Î” +ve (delta positive). If the total energy put in is less than the energy created, then the substance warms up (it is exothermic). This is expressed as Î”
-ve (delta negative).
I will investigate eight different alcohols using an alcohol or spirit burner, to measure the energy change during burning them by measuring the change in temperature of some water held by a container. This container must have a value of specific heat capacity so I could calculate heat transferred to it as well. Probably the most conductive container available for use in the classroom is a calorimeter. As well as not wasting energy in the heating of the container, I could also try to stop heat from escaping the top and edges of the container by covering it with a fitting lid. I will try to prevent the wind from blowing the flames to a different direction so all the windows must be shut. HYPOTHESIS
More energy is released as more bonds are formed, below is the list of approximate energy required to break and form all bond involved in burning alcohols
TYPE OF BOND ENERGY REQUIRED TO BREAK THE BOND (j)