Investigating the alcohols that use the most amount of energy to burn.

E=mcθ

Where m= the mass of the water, θ= the temperate rise and c= the specific heat capacity of the water).

Preliminary Results

Now that we have found the amount of mass lost for each alcohol we are able to calculate the energy produced in amount of energy per gram and the amount of energy per mole.

Methanol

Methanol energy produced                = mass of water * 4.2 * θ

                                        = 20 * 4.2 * 12

                                         = 1008J

So amount of energy per gram         = energy produced (J) / mass lost (g)

                                        =1008 / 1.5

                                        = 672 J/g

So amount of energy per mole        = energy per gram * relative molecular mass

                                        = 672 * 32

                                        = 21, 504 J/mol or 21.504 KJ/mol

Ethanol

Ethanol energy produced                = mass of water * 4.2 * θ

                                        =20 * 4.2 * 14

                                         = 1176J

So amount of energy per gram         = energy produced (J) / mass lost (g)

                                        =1176 / 1.5

                                        = 784 J/g

So amount of energy per mole        = energy per gram * relative molecular mass

                                        = 784 * 46

                                        = 36,064 J/mol or 36.064 KJ/mol

Butanol

Butanol energy produced                = mass of water * 4.2 * θ

                                        = 20 * 4.2 * 16

                                         = 1344J

So amount of energy per gram         = energy produced (J) / mass lost (g)

                                        =1344 / 1.5

                                        = 896 J/g

So amount of energy per mole        = energy per gram * relative molecular mass

                                        = 896 * 74

                                        = 66,304 J/mol or 66.304 KJ/mol

Propanol

Propanol energy produced                = mass of water * 4.2 * θ

                                        = 20 * 4.2 * 19

                                         = 1596J

So amount of energy per gram         = energy produced (J) / mass lost (g)

                                        =1596 / 1.5

                                        = 1064 J/g

So amount of energy per mole        = energy per gram * relative molecular mass

                                        = 1064 * 60

                                        = 63,840 J/mol or 63.840 KJ/mol

Now that I have calculated the amount of energy used per mole I can draw up a final table of results that I can draw my graph from.

Prediction

After analysing my preliminary results and my background information I think that the Butanol will give off the most energy per mole. I think this because Butanol has the highest relative molecular mass, we know this because:

Methanol – CH3OH        =32

Ethanol – C2H5OH        =46

Butanol – C4H9OH        =60

Propanol – C3H2OH =74

This is because C =12, H is equal to 1 and O is equal to 16.

Apparatus

Thermometer

Tin Can

Stop Clock

Top Pan Balance

Methanol, Ethanol, Butanol, Propanol

Calculator

Methodology

• Measure the mass of the first alcohol and then record the mass

• Burn the alcohol under 50 ml of water in a tin can

• Do this for five minutes and then measure the temperatue

• After five minutes take the alcohol away and measure the mass of

• the alcohol remembering o take away the mass of the tin can

• Work out the change in mass

• WE then work out the energy give out per gram and then per mole.

• Do this for the other 3 alcohols

Results

To calculate energy in grams we use:

(mass of water * 4.2 * θ)  /  decrease in mass

where θ = the rise in temperate

Methanol = (50 * 4.2 * 71) / 3.02                = 4937 J/g

Ethanol = (50 * 4.2 * 74) / 1.92                = 8093.75 J/g

Propanol = (50 * 4.2 * 73) / 1.98                = 7742.42 J/g

Butanol = (50 * 4.2 * 26) / 0.61                = 8950.82 J/g

Pentanol = (50 * 4.2 * 64) / 1.42                = 9464.78 J/g

To calculate energy per mole we use

energy per gram * relative molecular mass.

Methanol = 4937 * 32         =136,320 J/mol

Ethanol = 8093.75  * 46         =372,312.5 J/mol

Butanol = 4937 * 74                  =662,360.68 J/mol

Propanol = 4937 * 60         =464545.2 J/mol

Analysis

From my graph I can see that Butanol (CH2  * 4) gives out the most amount of energy per mole. Butanol gives out the most amount of energy per mole because it has the most amount of atoms meaning a higher atomic mass. With a higher atomic mass we get higher bond energy, if there is high bond energy the alcohol is going to use a high amount of energy per mole. I know that because we are breaking bonds and we found that Butanol is giving out energy the process of breaking bonds is known as an exothermic reaction.

Evaluation

I think that this experiment could have been improved if we used more alcohols say something like 8 or 9 different alcohols to provide us with a larger scale of results, I think this would have improved the experiment because we would have had more results to analyse and conclude. A way in which this experiment could have been conducted better would be to have more accurate measuring facilities and a way in which we could more accurately calculate the energy per mole.