Alcohol Combustion Plan
Comparing the enthalpy changes of combustion of different alcohols
Aim
In this experiment I will investigate the enthalpy changes of combustion. In particular I will be investigating the enthalpy change of combustion for different alcohols. I hope to investigate some of the homologous series alcohols, as well as a few structural isomers of these alcohols.
Background & theory
Enthalpy cannot be measured. What we can actually measure is the enthalpy change from the reactants to the products. This is the quantity of energy transferred to or from the surroundings. The energy is usually in the form of heat, so the surroundings either cool down or heat up.
The two kind of enthalpy changes include exothermic, and endothermic. Exothermic is where energy is transferred to the surroundings (this has a negative enthalpy change because we say that it has lost energy).
Endothermic is where energy is taken in from the surroundings (this has a positive enthalpy change as we say that it has gained energy).
The following diagrams show these two reactions graphically:
Enthalpy change is represented by the symbol ∆H. (∆ is ‘the change in’ the ‘H’ is for enthalpy)
The unit for enthalpy change is measured in Kilojoules per mole. For example if an alkane has a combustion enthalpy change of +296Kjmol-1 then the alkane takes in 296kJ of energy, from its surroundings, for every mole that is burnt.
Enthalpy changes can easily be measured using equipment in a school laboratory. We can set up an experiment so that energy is transferred to or from water. To actually work out the enthalpy change of combustion of this kind of reaction we can use the following equation
Energy transferred = cm T c = specific heating capacity of water (4.17Jg-1K-1) m = mass of water (in grams)
∆T = change in temperature of the water.
Enthalpy change depends on the bonds that are being broken and the bonds that are being formed in a chemical equation.
For example the
Aim
In this experiment I will investigate the enthalpy changes of combustion. In particular I will be investigating the enthalpy change of combustion for different alcohols. I hope to investigate some of the homologous series alcohols, as well as a few structural isomers of these alcohols.
Background & theory
Enthalpy cannot be measured. What we can actually measure is the enthalpy change from the reactants to the products. This is the quantity of energy transferred to or from the surroundings. The energy is usually in the form of heat, so the surroundings either cool down or heat up.
The two kind of enthalpy changes include exothermic, and endothermic. Exothermic is where energy is transferred to the surroundings (this has a negative enthalpy change because we say that it has lost energy).
Endothermic is where energy is taken in from the surroundings (this has a positive enthalpy change as we say that it has gained energy).
The following diagrams show these two reactions graphically:
Enthalpy change is represented by the symbol ∆H. (∆ is ‘the change in’ the ‘H’ is for enthalpy)
The unit for enthalpy change is measured in Kilojoules per mole. For example if an alkane has a combustion enthalpy change of +296Kjmol-1 then the alkane takes in 296kJ of energy, from its surroundings, for every mole that is burnt.
Enthalpy changes can easily be measured using equipment in a school laboratory. We can set up an experiment so that energy is transferred to or from water. To actually work out the enthalpy change of combustion of this kind of reaction we can use the following equation
Energy transferred = cm T c = specific heating capacity of water (4.17Jg-1K-1) m = mass of water (in grams)
∆T = change in temperature of the water.
Enthalpy change depends on the bonds that are being broken and the bonds that are being formed in a chemical equation.
For example the