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How boiling points change as the number of carbons change

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Jasdeep Bains How boiling points change as the number of carbons change Aim: The aim is to find out how the boiling point changes as the number of carbons in an alcohol increases. Scientific Knowledge: Molecules exist as distinct, separate collections of matter. The bonds within a molecule are typically quite strong, such that it's usually necessary to heat a molecule to very high energies before the bonds begin to break. For example, water is stable to decomposition to hydrogen and oxygen up to temperatures well above 500 C. In contrast, the forces between molecules tend to be relatively weak. If we chose an arbitrary scale in which the bonds between atoms within a molecule are set at 100, then the forces between molecules range between 0.001 and 15. In other words it generally takes far less energy to separate molecules from one another than it does to take molecules apart. The forces between molecules are called intermolecular forces. Intermolecular forces are the forces of attractions that exist between molecules in a compound. These cause the compound to exist in a certain state of matter: solid, liquid, or gas; and affect the melting and boiling points of compounds as well as the solubility of one substance in another. ...read more.


Collect and set up all apparatus including goggles. 2. Get an alcohol and pour 50ml of it in the round bottom flask 3. Switch on the Heating Mantle for 5-10 seconds 4. Keep switching it on and off otherwise it will get too hot 5. Wait until the first drop of alcohol comes out of the tube into the beaker 6. Record the reading on the thermometer 7. Remove the alcohol from the experiment. 8. Let everything cool down 9. Repeat all of the above with a different alcohol. 10. Once all alcohols have been used, clear up. Actual results from chemistry book: Alcohol No. Of carbons Boiling point ( c) Methanol 1 65.1 Ethanol 2 78.6 Propanol 3 105.5 Propan-2-ol 3 82.5 2 Methyl propan-2-ol 4 82.4 Butanol 4 117.3 Pentanol 5 138.1 Hexanol 6 158.1 Results: Alcohol No. Of carbons Preliminary work ( c) Method 2 ( c) Methanol 1 70 64 Ethanol 2 80 82 Propanol 3 95 102 Propan-2-ol 3 98 85 2 Methyl propan-2-ol 4 115 85 Butanol 4 98 115 Pentanol 5 110 135 Hexanol 6 110 155 1. 1. Fair test: To make it a fair test I should use the same amount of alcohol for each method. ...read more.


After every alcohol was used the equipment will have been washed. If the equipment was not properly dried using some kind of towel the water could easily mix with the alcohol. This would also cause high or low boiling points. Further work: Apparatus: Thermometer Heating mantle Beaker Test tubes Goggles Boiling tube Alcohols Paraffin Diagram: Method: 1. Collect all apparatus including goggles. 2. Fill the boiling tube with 50ml of alcohol, place a thermometer in it and put it to one side. 3. Fill a beaker with 100ml of paraffin, clip it in the stand and place it above the heating mantle. 4. Place the boiling tube containing the thermometer within the beaker. 5. Start up the heating mantle 6. Let the experiment take place until the paraffin boils. 7. Check thermometer and record the results. 8. Clean boiling tube, thermometer and beaker. 9. Repeat all of the above with a different alcohol. 10. Once all eight alcohols have been used, clear the equipment up. Fair test: To make it a fair test I should use the same amount of alcohol for each method. For method two I should make sure each alcohol receives the same amount of heat. Safety: For safety I have to wear goggles. You should tie back any long hair. You should not touch the heating mantle when on or hot - do not touch any hot equipment. ...read more.

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