To investigate the amount of heat released in the burning of fuels: ethanol (C2H5OH), propanol (C3H7OH) and butanol (C4H9OH).

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Plan

------------------------------------------------AIM----------------------------------------------

To investigate the amount of heat released in the burning of fuels: ethanol (C2H5OH), propanol (C3H7OH) and butanol (C4H9OH).

-------------------------------------------BACKGROUND----------------------------------------

ALCOHOLS

Ethanol, propanol and butanol are members of a homologous series of compounds known as alcohols. They have a general formula, CnH2n+1OH. They all react similarly and have similar physical properties.

MOLECULAR STRUCTURES                              

Ethanol: (C4H9OH)   

             H   H

       H – C – C – O – H

             H   H            

               

Propanol: (C3H7OH)

             H   H   H

       H – C – C – C - O – H

             H   H   H                              

     

Butanol: (C4H9OH)

             H   H   H   H    

       H – C – C – C – C - O – H

             H   H   H   H        

 

Energy is released when the bonds are formed between the new water and carbon dioxide molecules. The amount of energy produced by such exothermic reactions can be calculated by using the mass of the water x rise in temp x SHC (specific heat capacity). The specific heat capacity is the number of joules required to heat one gram of water by 1°C. Water has been chosen because it is safe, readily available, and has a reliable specific heat capacity of 4.2Kj

The reaction that is involved in burning alcohols is exothermic because heat is given out. For this reason the reactant energy is higher than that of the product.

BOND ENERGIES

To calculate the ideal energy released through such an experiment it is necessary to know the amount of energy that is required to break each bond bonds.

                 

TYPE OF BOND                               BOND ENERGY (kJ/mol)

C-H                                                               410

C-O                                                               360

O-H                                                               510

O=O                                                               496

C=O                                                               740

C-C                                                               350

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--------------------------------------POSSIBLE VARIABLES-----------------------------------

--         Type of Alcohol (Selected Variable)
--         Container size/Volume of water
--         Type of container
--         Volume/Mass of alcohol
--         Distance between wick and container
--         Starting temperature of water

FAIR TEST?

A fair test was maintained by keeping the above variables (apart from type of alcohol) constant in each experiment.

Altering the volume of water alters its mass, therefore affecting the equation: mass of water x rise in temp x SHC (specific heat capacity), and affecting the ability of the heat to be conducted. It is therefore easier to use the same amount of water ...

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