Alcohol is used as thermometric liquid because :
- Its freezing point is -117 degree C so it can be used in very cold places.
- Its expansion is six times more than that of mercury.
- Its cheaper than mercury.
The liquid used can be pure ethanol, toluene, kerosene or isoamyl acetate, depending on manufacturer and working temperature range. Since these are transparent, the liquid is made more visible by the addition of a red or blue dye.Alcohol thermometers are also inexpensive and durable. They are typically not as accurate as mercury thermometers because of the alcohol's susceptibility to evaporation, polymerization potential and capillary separation. Their primary advantage is safety to humans and the environment.
So, alcohol, which freezes at temperature below the point where water freezes, was used. The red colored or silver line in the middle of the thermometer moves up and down depending on the temperature. The thermometer measures temperatures in Fahrenheit, Celsius and another scale called Kelvin.When you're feverish, your whole body is with a higher temperature than normal. The reason you can't take your own temperature with your hand is because the hand is the same temperature as your head/face. You won't be able to detect a difference in temperature between them.
When you place a thermometer in hot water the molecules expand making more volume. The more temperature there is the more energy is given to the particles causing them to spread out, so the thermometer rises.Rectal thermometers, which go into your rear end, are the most accurate, but they can be uncomfortable. Armpit, ear, and forehead thermometers aren't as accurate. Most doctors think an oral thermometer, which you hold under your tongue, is best. Don't use an old glass thermometer.