Lesson three Oral topic: in the chemical laboratory Grammar

THERMOMETER SCALES

The concept of temperature variation dates from antiquity, although early measurements were based solely on the subjective sense of touch. Touch is only capable of detecting temperature differences between objects; it cannot provide quantitative temperature data. For example, you may be able to tell if a person has a fever by placing a hand on their forehead (лоб), but exactly how high is the fever? That question requires quantitative data; our senses can mislead us, but a thermometer can give us that data.

Gabriel Fahrenheit (German, 1686-1736) devised the Fahrenheit scale, the oldest common temperature scale, in about 1714. (Prior to this, Galileo Galilei had invented an open tube thermometer in about 1593.) One of Fahrenheit` s innovation was to use mercury, which made the liquid column easy to see. Previously, people had had difficulty sealing mercury – containing tubes.
Fahrenheit established his temperature scale by selecting reference points he could reproduce. He designated a freezing ice-snow-salt-water mixture as 0°F because this was the lowest temperature he could create in his workshop. Several stories purport to explain his selection of the reference point for 100°F; my favorite is that he selected the body temperature of a cow, a measurement that interested him and other in the agricultural community. Starting with these primary reference points, Fahrenheit determined values of 32°F for the freezing point and 212°F for the boiling point of water.
Anders Celsius (Swedish astronomer, 1701- 1744) developed a different thermometer scale in 1742. Celsius designated the freezing and boiling points of water as 0°C and 100°C, respectively. His scale was originally called the centigrade scale because centi-means 1/100^th part, and the reference points span 100 degrees. The Celsius scale has been adopted worldwide and is the official metric temperature scale.
The third temperature scale was the invention of Englishman Lord Kelvin (born William Thompson, 1824-1907). Lord Kelvin devised his scale in 1848. It is identical to the Celsius scale, but all temperatures are 273 degrees higher. Thus, the freezing point of water is 273 degrees K, the boiling point 373 degrees K. This thermometer scale was derived from observation of gases.

part v