# This experiment is to investigate how much energy alcohols give off when they are burnt. When burnt the alcohol reacts with oxygen to give the products Carbon Dioxide and Water.

Robert Bennett 10A5 Dame Alice Owens School

Chemistry Coursework: Alcohols and Energy it takes to break them

This experiment is to investigate how much energy alcohols give off when they are burnt. When burnt the alcohol reacts with oxygen to give the products Carbon Dioxide and Water.

Chemical Formula:

Structural formula (methanol)

Structural formula (ethanol)

The structural formulas for the rest of the group of the homologous alcohols have the same structure, with more carbon and hydrogen atoms arranged in the same way. In an exothermic reaction heat is given out when the new bonds are formed. When bonds are broken the heat energy is taken in so the reaction is endothermic. In this experiment we have an exothermic reaction because it produces more energy forming new bonds than breaking them. So it gives out heat energy. The energy output is found by subtracting the energy produced to form the bonds from the energy produced to break the bonds. This is known as the enthalpy, which is always negative as heat is “lost” from the reaction. This can be shown in this rough energy level diagram.

Chemical Principles By Master & Slowinski suggest that heat used by products (Hp) subtracted by heat used for reactants (Hr) equals the enthalpy (? H). It can be shown in this chemical formula.

Hp   -  Hr     =     ?H

However doing a practical experiment is not the only way to work out the enthalpy of an alcohol. We can show it in energy level equations, using figures from textbooks to tell us the energy in kJ/mol. This is a good way to predict what results we might get from our experiments if they go according to plan. Here is an energy level equation, how to work out the energy produced by burning Methanol.

In our practical experiment to work out the amount of energy released from the reaction we need to use this equation.

Heat Energy  =  mass of water  x  specific heat capacity  x  change in temperature

= ________ Joules

This equation is only assuming that the energy released by the alcohol we are burning is the same as the heat energy absorbed by the water.

The specific heat capacity is the amount of energy required to heat the substance. The specific heat capacity of water is 4.2J/°C because that is the reliable figure that I have researched

The bonds are made due to the forces of attraction between the atoms. This can be either covalent bonding, where the ...