[TRAY]

I have been doing an investigation regarding enthalpy changes. We (high school class) are required to burn various fuels, etc., and in doing so also find the change in enthalpy. For example, in one experiment Methylated Spirits was burnt for 10 minutes whilst heating up 100mL of water. Therefore, based on what we have been taught:
[tex]\Delta H = mc\Delta T[/tex]

So, if there are 100g of water, the specific heat capacity is 4.18, and the change in temperature is 75.7, then:
[tex]\Delta H = 100(4.18)(75.7)[/tex]
[tex]\Delta H = 41.8kJ[/tex]

However, because we were burning the Methylated Spirits for 10 minutes, we could only calculate the change in enthalpy to that point. I believe this is a problem because the water reached boiling point, and so the temperature plateaued for around a minute. The graph is attached to this post.


The question of all this, is whether this will affect the result of 41.8kJ. I understand there is a latent heat of vaporisation, but because the water didn't fully 'transform' into a gas, is it even possible to use this? Also, as I am a high school student and have only just started this unit, I apologise for any fundamental misunderstandings of enthalpy.

[Corribus]

It's good that you are paying attention to what you are doing.

You could ignore the vaporization of water and accept the error.

You could weigh the water after the experiment to get an idea of how much of the water vaporized and incorporate that along with the heat of vaporization to get a more accurate measurement of the total heat transferred to the water.

Probably the best thing would be to just redo the experiment using a larger volume of water.

[TRAY]

Okay. Thank you very much for the *delete me*