• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4

# Energy of different alcohols.

Extracts from this document...

Introduction

Energy of different alcohols

The measurements recorded were:

• Volume of water in the can
• Starting temperature of water
• Final temperature of water
• Change in temperature of water
• Start mass of alcohol and spirit burner
• Final mass of alcohol and spirit burner
• Change in mass of alcohol and spirit burner.

Using the mass of water used (1 cm3 water has a mass 1g), temperature rise of the water and specific heat capacity of water (4.2 J raises the temperature of 1g of water by 1°C) the energy transferred from burning the fuel to the water was calculated.  This was then converted energy released per mole of fuel (kJ/mol) using the mass of the fuel used and the formula mass of the alcohol.  These are the figures given in Table 1.  The figures from five groups were averaged.

Table 2 Formula masses of the alcohols used

 Alcohol Formula mass Methanol 32 Ethanol 46 Propanol 60 Butanol 74 Pentanol 88 Hexanol 102

As the alcohol molecule being burnt gets bigger the energy released when it is burnt goes up (Graph 1).

The line of best fit on graph 2 shows that the number of carbon atoms in the alcohol is proportional to the energy released on its combustion.

Breaking and making bonds

To break bonds energy is needed.

Middle

3OH + 1.5O2                    CO2 + 2H2O

Ethanol

C2H5OH + 3O2                    2CO2 + 3H2O

Propanol

C3H7OH + 4.5O2                  3CO2 + 4H2O

Butanol

C4H9OH + 6O2                     4CO2 + 5H2O

Pentanol

C5H11OH + 7.5O2                  5CO2 + 6H2O

Hexanol

C6H13OH + 9O2                   6CO2 + 7H2O

Table 4 Theoretical energy released when alcohols burnt

Calculated from bond energies

 Alcohol Energy (kJ/mol) Methanol 658 Ethanol 1276 Propanol 1844 Butanol 2515 Pentanol 3130 Hexanol 3748

Table 4 shows that the theoretical energy released from alcohol combustion increases as the size of the alcohol molecule increases.  This is because the bigger molecules have more bonds to be broken and more bonds are made in the products of the reaction (water and carbon dioxide).  The extra bonds that are broken in the alcohol with more carbon in it need more energy but the products release even more energy as they formed therefore the overall energy released by the reaction (combustion) goes up.  The results of the experiment showed the same pattern but the results were much lower due to inefficient energy transfer to the water (Graph 3).  Table 5 shows that a

Conclusion

• The wick varied in length.

The wick could have been adjusted to the same length before each alcohol was burnt.

• Heat from the flame could have escaped out to the sides of the spirit burner.

Draught excluders could have been put up around the spirit burner and can.

• The can was made of copper which meant that it absorbed and transferred heat well to the water but it also lost heat to the air.

The can could have been insulated at the sides.  The can already had a lid.

Although the results are low they do show a pattern of increasing energy transfer to water with increasing carbon content of the alcohol, suggesting some reliability.  If the results were completely unreliable they would not show any pattern.  The trend in a decreasing percentage energy transfer to the water compared to the theoretical with increasing size of the alcohol molecule may have been due to the alcohol burning faster causing increased heat loss and decreased heat transfer.

The results were good enough to come to a firm conclusion but further evidence could be provided with further reading from this experiment and from another experiments.  The liquid in the can could have been changed to something else with a different heat capacity.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related GCSE Electricity and Magnetism essays

1. ## Investigation into Energy Released From Burning Various Alcohols.

4 star(s)

that is used/released when each bond is made/broken. Bond Kj/Mole C-H 413 C-O 358 O-H 464 O=O 497 O-H 464 C=O 745 C-C 346 * I multiplied the number of each bond that occurred for a particular molecule by the energy it used/released, to get how much energy was used/released in total through that bonding.

2. ## To investigate which fuel gives out the most energy when burnt. We are burning ...

1 X C-O (1 X 360) 1 X O-H (1 X 460) 6 X 0=0 (3 X 496) 3 X C-C (3 X 350) = 8536KJ/MOL Bonds Made 8 X O=C (8 X 740) 10 X O-H (10 X 460)

1. ## Burning Alcohol

One approach to preventing heat loss to the air would be to do the experiment in a vacuum, but that in itself is a problem, because creating a large enough vacuum and stabilising would be difficult without very expensive equipment.

2. ## Investigating the heat of combustion of a series of Alcohols

Record the highest temperature of the water. 8. Repeat steps 1-7 using Propanol, Butanol, Pentanol and Hexanol. The amount of water and the amount of alcohol need to be kept the same for all of the experiments. Results Table Alcohol Temperature of water at start (oC)

1. ## Finding a material's specific heat capacity

Because of this, a voltmeter was used to measure the actual voltage and this has the advantage of being far more accurate than the value claimed by the power supply. An electric heat supply is very accurate as, due to the E = IVt formula, the amount of energy put

2. ## Resistance of Carbon Putty.

Conclusion: From my experimental evidence I can conclude that there is a definite relationship between the length of carbon putty and its resistance to electricity. The longer the wire the greater the resistance. Graphically this appears to be an almost directly proportional relationship although some of my results appeared to

1. ## How does the Relative Molecular Mass change in heat combustion of an alcohol?

This means that in every case, the energy used (J) = 4.18 x 200 x 40 = 33440 J = 33.44 KJ To give us the energy output per mole, we then need to find out how many moles have been used, and divide this into the energy used.

2. ## Investigating The Heat Of Combustion Of Alcohols.

we see that the total energy produced from the combustion of methanol is 589.5kJ. This energy is used to heat up the water in the copper calorimeter. Some energy will also be used to heat up the copper calorimeter. For example with ethanol the equation would be: ethanol + oxygen carbon dioxide + water + energy CH3CH2OH + 3O2 (g)

• Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to
improve your own work