scale. The ice and steam point have values ° F and ° F, respectively, on the Fahrenheit scale and °C and ° C on the Celsius scale. On the Fahrenheit scale, there are equal intervals between two reference points, and on the Celsius scale, there are . Fig.
. A plot of Fahrenheit temperature (t F ) versus Celsius temperature (t c ). A relationship for converting between the two scales may be obtained from a graph of Fahrenheit temperature ( t F ) versus celsius temperature ( t C ) in a straight line (Fig. .
), whose equation is t t F C – ( . ) . IDEAL-GAS EQUATION AND ABSOLUTE TEMPERATURE Liquid-in-glass thermometers show different readings for temperatures other than the fixed points because of differing expansion properties. A thermometer that uses a gas, however, gives the same readings regardless of which gas is used.
Experiments show that all gases at low densities exhibit same expansion behaviour. The variables that describe the behaviour of a given quantity (mass) of gas are pressure, volume, and temperature ( P, V , and T )(where T = t + . ; t is the temperature in ° C). When temperature is held constant, the pressure and volume of a quantity of gas are related as PV = constant.
This relationship is known as Boyle’s law, after Robert Boyle ( – ), the English Chemist who discovered it. When the pressure is held constant, the volume of a quantity of the gas is related to the temperature as V/T = constant. This relationship is known as Charles’ law, after French scientist Jacques Charles ( – ). Low-density gases obey these laws, which may be combined into a single named after the British scientist Lord Kelvin.
On this scale, – . ° C is taken as the zero point, that is K (Fig. . ).
The size of unit in Kelvin and Celsius temperature scales is the same. So, temperature on these scales are related by T = t C + . ( . ) .
THERMAL EXPANSION You may