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Experiment to measure the Specific
Latent Heat of Vaporisation of Water
| 1.
Preparation: |
a) |
Learn the
definition of specific latent heat. |
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b) |
It is
usually found to be easier to measure the quantity of heat given
out when steam condenses than to measure the quantity of
heat needed to vaporise water. (To see that this is true, try to
design an experiment in which you measure the quantity of heat
needed to vaporise 1kg of water.) |
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c) |
See part
3 below. |
| 2. |
Set up apparatus as
shown in the diagram below; it might be convenient to use rubber
tubing for the delivery tube. Be careful, it will get HOT ! |
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The experiment consists of passing the steam
(assumed to be at 100°C) through cold water where (some of) it
will condense. |
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Heat the water to boiling point and leave it
boiling for a few minutes before putting the container of
cold water in place.
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| 3. |
a) Why must you wait for a few
minutes before putting the container of cold water in place? How
will you know when the apparatus is ready for use? |
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b) Derive an equation which will allow you to
calculate the specific latent heat of vaporisation of water from
your results. Think about the main sources of error in an
experiment like this and how to reduce the effects of these
errors on the precision of the final result. |
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