Determining the heat of combustion
11IB chemistry HL
Raw Data
-Wax
-Ethanol
-Butanol
Data processing
-Wax (C25H52)
-Ethanol (C2H6O)
-Butanol (C4H9OH)
Error
Conclusion and Evaluation
There are many fuels in the world and we use fuel everyday in our life. However some fuels are very useful and some are not. Usually useful fuel means the fuel that is very efficient in a small amount. To know the efficiency of each material, we measured the changes of mass and temperature when we burn them. And we calculated changing energy by using the equation that we learned in the class by using our measurements. And we calculated the heat of combustion to know the efficiency of the material. ...
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-Butanol (C4H9OH)
Error
Conclusion and Evaluation
There are many fuels in the world and we use fuel everyday in our life. However some fuels are very useful and some are not. Usually useful fuel means the fuel that is very efficient in a small amount. To know the efficiency of each material, we measured the changes of mass and temperature when we burn them. And we calculated changing energy by using the equation that we learned in the class by using our measurements. And we calculated the heat of combustion to know the efficiency of the material. We also used the data booklet value for the standard enthalpy of combustion of each material to get the errors in our experiment. Errors in our experiment were usually over 20 percent which is quite large.
Before we heated the water, we made the temperature of water below than 10°C with ice to see the changes of temperature more efficiently. If we just heated it in normal temperature such as 20°C, we couldn’t see the changes of temperature well, and it could take more time to heat it. We also measure the changes of mass of material to see how much we burned.
We put some ice in the water to make the initial temperature of water as lower than 10°C. When the temperature decreased up to 10°C, we took out ice from the water. After we took out the ice and fill the cylinder up to 200ml of water, the temperature was higher than 10°C because the temperature of the water changed very quickly. We measured the temperature of water and then we hang the tin can on the hanger, so the temperature might increased again during we set up all the experiment systems. So we should measure the temperature of water when we set up all the things. For example we should measure it after we turn the light on the candle wax and hang the tin can on the hanger.
We measured the final temperature to see the changes of the temperature. We blew out the candle when the temperature reaches 35°C, and we measured the highest temperature reached as the final temperature. When the temperature reaches 35°C, we quickly blew out the candle. However we are not accurate as the machine so we might didn’t blow out it when it reaches exactly 35°C. Also it was difficult to measure the highest temperature of it after we blow it out. Even though we kept watching it, the temperature changes so quickly, so our measurements are not correct 100%.
In our experiment we didn’t measure the mass of tin can. If we measure the mass of it, we could get more precise measurement compare to the standard enthalpy of combustion. Our errors are quite large, so I think one of reason is that we forgot the measure the mass of tin. So we should study and think more about the experiment before we do it. We could calculate how much heat we got by adding the changing energy of water and the changing energy of the tin can, if we measured the mass of can.
At the end of the experiment, we measured the mass of candle to know how much of them were burned. During and after we blow out the candle, some of liquid were might evaporated. Such as ethanol and butanol are volatile liquid, and the fact that the lamp was hot indicates that some of it would have evaporated. So they are burned and evaporated more after we measure the temperature. Another fact that we should consider is that not only the water was being heated, but also the thermometer, stirring rod and the tin can were also being heated. We should consider that they were also heated, so we should measure how much heat were used to heat them. Also some other heat would have been lost round the sides of the tin can, and from the water to the atmosphere. Due to our room temperature are different from the temperature of water.
The good thing that we did in our experiment is that we made some space when we set up the large metal can to surround the candle. As we make some space under the large can by putting some flat cylinder under the can, the candle burned more quickly and well. If we didn’t make the space for it, air might stuck in there so it would take more time to reaches up to 35°C.
