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Investigation on the combustion of Alcohols.

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Investigation on in to the combustion of Alcohols Hypothesis As the number for carbon atoms in alcohol increases the more energy is released. I am going to conduct an experiment, which will allow me to compare the heat energy given off by three alcohols, those being ethanol, propanol and butanol. These alcohols have a difference of one carbon atom within there atomic structure. I am going to investigate the amount of energy given out per mole once we burn the alcohol, which is the enthalpy of combustion (?H c). This can be supported with the calculations of the bond energies We know that chemical bonds are broken in reagents for this to happen energy must be put in and also chemical bonds are made in the products when this happens and energy is given out. How much energy has to be put into break a given bond or how much is given out when this bond is made depends on the strength of the bond The net energy change ?H depends on the relative strength of the bonds being made and broken. Exothermic reactions Exothermic reactions stored chemical energy is converted into heat energy because the bonds being broken are weaker than the bonds being formed. ...read more.


Safety Precautions In order to ensure safety throughout the experiment I will wear safety goggles and make sure that the hot water is handled carefully therefore ensuring that there is no spills or burns. Obtaining evidence During the experiment, I obtained two sets of results, which will enable to have a wider range of results. During the experiment, I made sure that I wore safety goggles and I handled the hot water with care. The results I took are in the tables below. The temperature indicates the temperature of the beaker of water and the mass indicates the mass of the spirit burner before and after the experiment. Constants that were kept: During the experiment, I kept the length of the wick 1cm and the distance between the wick and the beaker was 10cm. The mass of the water was 100g the length of time was 100 seconds. Ethanol Starting temperature 17 17 End Temperature of Water 39 38 Temperature Change of Water 22 21 Starting mass 180.89 181.56 Ending Mass 178.06 179.09 Mass Change 2.83 2.47 Propanol Starting temperature of Water 20 20 End Temperature of Water 45 43 Temperature Change 25 23 Starting mass 179.60 180.35 Ending Mass 176.50 177.23 Mass Change 3.1 3.12 Butanol Starting ...read more.


Also, the water would have conducted through the beaker and also through convection through the surface of the water. And also, the water would have escaped through radiation. Then heat could have been lost through the flame as in my experiment there was a ten centimetre gap between the wick and the beaker, therefore heat loss could have been lost through that. Therefore, these factors made the experiment unsuitable. I improvements I could have made to the experiment I would have made, is that I would insulate the beaker with foil and cotton wool to reduce the heat loss. Via conduction and radiation. I would place a lid over the beaker to stop evaporation and I would use digital thermometer to record the readings. I would use a pipette to measure the volume of the water this would therefore make it more accurate than a measuring cylinder. And also I would reduce the distance between the sprit burner and beaker to reduce the amount of heat lost. To extend this investigation I would extend the range of alcohols used. I would use the next to after for example pentanol and hectanol and perhaps go as far as octanol. The prediction for that experiment would be the same as this one. As you increase the carbon atoms the more energy that is released. 1 ...read more.

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