Question from my textbook: Jason says 'The mercury in the thermometer can be replaced by coloured water. The thermometer will function well after recalibrating using a similar method to calibrating a mercury-in-glass thermometer." Comment on his idea.
The answer is NO, but why?
Please use simple english to answer my question, as I am only grade 9, I haven't learnt much about physics, therefore I may not understand some technical words. Thanks!
Best Answer
A mercury-in-glass thermometer is traditionally calibrated by measuring two temperatures: the freezing point of water (0°C), and the boiling point of water (100°C).
There's an obvious reason why this won't work for a water-in-glass thermometer: the water in the thermometer will freeze when when you stick it in the ice bath, and boil when you stick it in the boiling water, and in neither case will you get a good reading.
There's also a less-obvious problem with measuring the freezing point: even if you try to measure the height of the water column just before the water freezes, you won't get good information: water has a maximum density around 4°C, and expands as it cools from there to the freezing point. The height of the water column just before it freezes will be about the same as it was at 8°C.