Why do thermometers contain alcohol and mercury?
A thermometer is an instrument used to measure the temperature. Commonly used thermometers include mercury thermometer and alcohol thermometer. Mercury and alcohol are the keys to making thermometers, called thermometers. The thermometer that can be used to measure temperatures is because it has hot and cold shrinking characteristics. With increasing temperatures, the volume of mercury and alcohol will expand significantly. It is recognizable in the thermometer that the height of the mercury column or the alcohol column increases. Thus, by carving only the appropriate etching, one can read out the corresponding temperature.
For a thermometer to be of a greater value, the measurement material needs to have two major characteristics: firstly, the change in the volume of a thermometer with a temperature change must be very sensitive, so that measure very small temperature changes; secondly, when measuring at low temperatures, the measuring material must not solidify into a solid; conversely, at high temperatures, the measurement does not turn into a gas. If not, then it cannot be used to measure heat.
For mercury and alcohols of the same mass, if they increase their temperature in turn by 1 ° C, the experiments found that the absorbed heat of alcohol is much greater than that of mercury, about 20 times. Therefore, the sensitivity of the change in temperature of the mercury column in the mercury thermometer is much greater than the column of alcohol in an alcohol thermometer. In scientific experiments or measuring the human body’s temperature, measuring the amount of heat absorbed or released by a thermometer is very small. Still, it must show the change of temperature, so generally use a hydro thermometer bank. With the same temperature change, the wine absorbs much heat and expands greatly, so the up and down variation of the wine column is much more pronounced than the mercury column. When measuring the ambient air temperature and water temperature, it is common to use alcohol thermometers.
Wine and mercury also have different properties: the alcohol “very cold” is very good; at a temperature of -117 ° C, it solidifies into solid, and mercury at a temperature of – 31 ° C has hardened, lost fluidity. In cold countries, the winter air temperature drops to approximately -40 ° C, so it is generally appropriate to use an alcohol thermometer to measure the air temperature. But mercury also has one advantage: it’s “more resistant to heat” than alcohol. The boiling point of mercury is 356.72 ° C; When the alcohol reaches 78.3 ° C, it will boil and quickly evaporate. In the case of high-temperature measurements, it is clear that mercury thermometers have a more accurate temperature measurement than alcohol thermometers.