Hot and cold
Hot and cold is more than a simple feeling, there is a lot more to it.
From a personal point of view, we feel warm if we received energy, and we
feel cold when we lose energy.
The objective measurement of hot and cold started by Newton in 1701,
when he used 0 for ice, and 12 for human body temperature. Temperature
scales were developed soon after and refined.
In 1714, Fahrenheit and Celsius scales invented.
Salt water freezes at 0oF, boils at 212oF
Pure water freezes at 0oC, boils at 100oC
William Thomson (1824-1907) (Baron Kelvin of Largs), developed 2nd law of
thermodynamics and the absolute temperature scale.
0 K - absolute zero, no lower temperature possible
273.15 K - assigned to triple point of pure water
Temperature and Heat
Application of temperature scales
Heat is indestructible energy measured in J that flows from
high-temperature places to low-temperature places. Two places are at the
same temperature if there is no net heat flow between them.
Temperatures are measured using properties of substances: expansion on
heating, phase transitions, and thermoelectrical properties (thermal couples).
Amounts of heat in systems are difficult to measure, because we do not
know their heat capacities at low temperatures. Relative amounts are usually
Due to applications of temperature measurements, the following laws are
Charles and Gay-Lusaac gas law
Boyle's law of gases
Industries built around temperature measurements (high, low, in between)
Temperatures are important parameters to have.