Essay Sample on Output and exothermic heat energy of methanol along
Of these, wind is a prime factor, as it would blow the flame from side to side and away from the can. Excess heat energy from the combustion reaction will be wasted on the air around the system and other objects – hands, table etc. Consequently, the system water will not receive much heat energy and the alcohol will needlessly burn away, releasing heat energy to the wrong place. To sustain a constant flame, heatproof mats (substituting for wind breakers) will be placed at strategic points to ensure that as little disturbance as possible is caused to the system.
The air temperature is also an important factor although it is very difficult to control. This is because the hotter the air is, the easier it will be to conduct heat and the less time it will take for the heat to reach the water (do not need to heat up the air to a high temperature but only to. Not to mention that less heat will be lost and the alcohol will not have to burn so much more of itself. The volume of water in the can is vital in the experiment and must be controlled to ensure the specific heat capacity is kept the same for all experiments.
Different volumes of water will have varied heat contents and will absorb more/less energy to raise their temperatures to a certain extent. Larger volumes of water (500g) will have a large amount of water molecules, each of which have the same individual heat capacities and these will form a large total specific heat capacity for the water. The 500g of water will then need to obtain a big quantity of heat to change it’s temperature meaning that alcohol mass is lost to produce this heat, whereas less mass would be lost and less energy would be required if a 200g water volume was heated (since it has smaller total specific heat capacity. )
Another factor that is also related to specific heat capacity is that other equipment in the experiment may absorb some of the heat energy lost from the combustion of alcohol. These would be the can and thermometer since they are an integral part of the system. When heat energy is released, it travels through the air and to the can, which has to take in the energy and then pass it to the water. But it does not transfer all of this heat energy to the water because the can itself takes some of it to suit it’s specific heat capacity. The remainder of the heat energy that enters the water may also go to the thermometer if it is touching the can.
To prevent more heat being taken from the water, we have to hold the thermometer such that it is not in contact with any part of the can. Another reason for this precaution is because we are only measuring the temperature of the water and if it is touching the can, then we are measuring the temperature of the can. Heat energy is lost by the water through the top of the can due to evaporation. As the water gets hotter (receiving heat energy), its molecules start to move around faster and faster, which causes them to break their weak intermolecular bonds.
Only the faster particles can achieve this and so they ‘break free’ of the liquid and evaporate near the surface. However, this evaporation lowers the average energy of the water molecules left and so the water becomes cooler. Subsequently, the heat energy produced by the combustion reaction does not really heat up the water (heat is drifting out of the top) and the alcohol burns for longer; decreasing in mass. To counteract this, a lid can be placed on top of the can so that the heat energy is contained within and little evaporation occurs.
Incomplete combustion is essentially not a serious factor but when there is a small quantity of oxygen around the reaction – then it will not form the proper products of complete combustion and the excess energy given out may be different. There is little we can do to prevent this although there should be enough oxygen in the atmosphere to support complete combustion anyway. Prediction: I predict that as the alcohol’s number of carbon atoms grow, the energy given out will increase and the mass of alcohol lost will decrease. The alcohol ethanol will lose the most mass in order to fulfil the energy necessary to raise the temperature of water.
So even a large mass of ethanol will not give out much exothermic heat energy meaning 1 mole of it will not as well. This is the energy chart for this: The alcohol octanol will lose the least mass when producing the energy needed to raise the temperature of water. So this means that a small mass of octanol will dissipate a huge amount of exothermic heat energy as will one mole of it. This is the energy chart for octonal’s combustion: So to repeat my prediction: I think that as the alcohols get more and more carbon atoms and different bonds, the energy they give out will increase and their mass loss will decrease when doing this.
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