Water shrinks at cold temperatures, but I wonder HOW MUCH water does shrink? We have an outdoor pool of 4x8m (1.5m deep) with 81cm of water. The water level has dropped 1cm in 4 days. Do we have a leak or has the water just shrunk?
Answer
Dear Karin,
The cubic expansion coefficient of a liquid indicates the relative volume by which the liquid shrinks (or expands) when it is 1 °C colder (or warmer). For water it is quite small compared to other liquids: at 20 °C it is only 0.00021. This means that a water height of 81.00 cm of water, if the temperature of the water were to drop by exactly 1 °C, would decrease to a height of 80.98 cm. For a difference of 10°C this becomes 80.83 cm, which means a subsidence of 0.17 cm. You may not be able to accurately determine the height to 0.10 cm, so you will hardly be able to measure the difference. You will hardly notice a difference of 0.17 cm, and this is already the case for a 10 °C difference!
It should also be mentioned that the coefficient of expansion of substances at temperatures other than 20 °C (slightly) can be different. This is certainly true for water. From 4 °C, water even starts to expand as it gets colder! Water is therefore most “compact” at 4 °C. Colder than this, the very special expansion behavior of ice begins to manifest.
A leak is indeed a possible explanation of the falling water level. A less gloomy possibility is that the water simply evaporated. This can now go faster in autumn due to the greater difference between water temperature and air temperature than in summer.
Kind regards,
Pieter Schevenels
Answered by
dr. ir. Pieter Schevenels
sound acoustics engineering
Agoralaan University Campus Building D BE-3590 Diepenbeek
http://www.uhasselt.be/
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