The thermometer must be <u>in contact with the ice/water only</u>
Explanation:
In this experiment in the lab, the aim is to measure the specific latent heat of fusion of water.
The specific latent heat of fusion of a substance is the amount of heat energy required to completely melt a certain amount of the substance, mathematically:
where
Q is the heat supplied to the substance
m is the mass of the substance
In this experiment, the aim is to measure the specific latent heat of fusion of water. In order to do that, a mix of ice/water is heated with a certain amount of heat Q, and then it is evaluated the amount of mass m that undergoes melting.
An important precaution that must be taken in this experiment is that the temperature of the water/ice mixture remains constant and equal to the melting point of ice (otherwise, part of the heat supplied to the mixture is used to increase the temperature of the water, resulting in an inaccurate measure of Q). Therefore, a thermometer must be used to check constantly the temperature, and this thermometer must be placed inside the ice/water mixture only (It should not touch the saucepan, whose temperature can be higher).
So, the correct answer is
in contact with the ice/water only
Learn more about specific heat:
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