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Introduction

Our aim is to find out which fuel out of the following 4 1. METHANOL - CH3OH 2. ETHANOL - C2H5OH 3. PROPANOL - C3H7OH 4. BUTANOL - C4H9OH Gives the most energy when it is burnt. 2. To find out if there is a correlation between energy and a certain number of carbons. Burning fuels is a combustion (oxidation) reaction: for example 2C H3OH + 302 2CO2 + 2H20 + ENERGY Reaction A chemical reaction takes place in two steps. STEP 1 The chemical bonds in the reactants are broken to release the atoms, which make the reactants. For this to happen we need to provide energy. One of the reactions that we must give it is called ENDOTHERMIC (Heat energy put in). H O H O H O H 2(H -C - O - H) + 3 (O=O) O H C H O H O H O H O H C The bonds that are broken are: C - H x 6= 413 x 6= 2478 C - O x 2= 335 x 2= 670 O - H x 2= 464 x 2= 928 O = O x 3= 498 x 3= 1494 5570 EACH CHEMICAL BOND HAS ITS OWN VALUE BOND ENERGY KJ/MOL H - H 436 C - H 413 C - C 347 C - O 335 O = O 498 O - H 464 C = O 740 STEP 2 O H O H O H O H C 2 C=O + 4 (H - O - H) ...read more.

Middle

fuel * Always 50cm3 of water * Same thickness of metal * Same colorimeter * Always 1gm of fuel * Start with coldwater each time Obtaining results Table Of Results Prediction For my prediction I have used lots of background knowledge and done some preliminary experiments. As you can see I have worked out the theoretical energy release for each alcohol and from these I would predict that as the number of carbon atoms go up so will the heat of combustion. I believe that the results will be proportional to the amount of carbon atoms. I believe this because every time you add an extra carbon bond you also add two more hydrogen bonds, which means that the relative molecular mass will increase as well. I also predict that this will be a constant amount. When I achieve my results I will need to figure out the actual amount of energy given out and the molecular mass plays a big part in this. Analysing I think my results tables and graphs clearly show the pattern that I have found in this experiment. That is that heat combustion does increase when the amount of carbon atoms increases. A table that answers the question more specifically and clearly is shown below: How many grams in one mole of each fuel? Fuel No. Of carbons Mass of 1 mole (g) ...read more.

Conclusion

As we proceeded with the experiment we came across two types of reactions: ENDOTHERMIC: A reaction that we must give it energy. This is when bonds break, and heat energy is put in. EXOTHERMIC: When new bonds are made energy is given out. We can prove this by using scientific knowledge because our scientific knowledge tells us that a chemical reaction takes place in two steps. The chemical bonds in the reactants are broken to release the atoms, which make the reactants. But for this to happen we need to provide energy. And the energies are as I said ENDOTHERMIC and EXOTHERMIC. We also found out that the prediction agrees with the conclusion because we predicted that the more carbon atoms a compound has the more energy it will release. Later on we investigated the experiment further and found out that Energy Joules/gm = 4.2 x 50 x temperature increase 4.2 is needed to increase the temperature of 1gm of water by 1C. Using this we found out that Butanol released 3255 Joules/gm. After this I can conclude that my initial prediction was actually right but I didn't allow for all of the experimental errors. I conclude that carbon atoms in alcohols do have an effect on the heat of combustion. As the amount of carbon atoms go up the heat of combustion does. This is because every time you add another carbon atom you are also adding 15 onto the relative atomic mass that plays a big part in calculating the end results. NAME:SUBHAN ALI 11-12-2003 SCIENCE COURSEWORK DR HOLMES ...read more.

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