Question

Answer the following question.

What is absolute zero?

Answer 1

Graph of pressure versus temperature (in °C) at constant volume.

Graph of volume versus temperature (in °C) at constant pressure.

1. When the graph of pressure (P) against temperature T (°C) at constant volume for three ideal gases A, B, and C is plotted, in each case, P-T graph is a straight line indicating direct proportion between them. The slopes of these graphs are different.
2. The individual straight lines intersect the pressure axis at different values of pressure at 0 °C, but each line intersects the temperature axis at the same point, i.e., at absolute temperature (-273.15 °C).
3. Similarly, graph at constant pressure for three different ideal gases A, B and C extrapolate to the same temperature intercept -273.15 °C i.e., absolute zero temperature.
4. It is seen that all the lines for different gases cut the temperature axis at the same point at - 273.15 °C.
5. This point is termed as the absolute zero of temperature.
6. It is not possible to attain a temperature lower than this value. Even to achieve absolute zero temperature is not possible in practice.