An alcohol thermometer utilizes the expansion and contraction of alcohol in response to temperature changes to measure the temperature. A number of different alcohols can be used, depending on the environment where the thermometer is being utilized, with ethanol being among the most common. This type of thermometer is very popular because it is non-toxic, unlike a mercury-in glass thermometer, and the contents will not pose a threat to human health or the environment if the thermometer is broken.