Scientist Jacques Charles experimented with a fixed amount of gas at constant pressure, when he increased the temperature of the gas, he found that the volume of gas was increased and the volume of gas decreased with decrease in temperature.
He repeated his experiment with a number of gases and every time he found the same behaviour. When he drew the graph between volume and temperature, he found a straight line. He concluded that the volume of a gas is directly proportional to the temperature.
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| Graphs of Charles’ law |
Then he repeated his experiment at a different pressure, this time also he found a straight line but with different slope. He found that with increasing the pressure the slop of straight line decreased, which means gases disobeyed his law at higher pressure.
Charles observed that the volume of gas decreased with decrease in temperature, so he was curious to find out what happens below zero degree. But at his time it was practically difficult to maintain such a lower temperature for this experiment. So he decided to do it mathematically. When he extrapolated the straight line obtained by V vs T graph, he found that all lines meet the temperature axis at -273.15°C.
Although the volume of gas decreased with decrease in temperature, it was impossible to obtain a negative volume corresponding to the negative temperature, because negative volume means gas doesn’t exist. On the basis of Charles law, the new scale of temperature was developed by Kelvin. In Kelvin scale temperature is given by (t°C+ 273.15)K.
And the imaginary temperature, at which according to Charles the volume of all gases is supposed to be zero, is defined as absolute zero in Kelvin scale.
In our next post we will see how we get benefited by his discovery.
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