Thermal Properties of Matter
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Question : 4
Total: 22
Answer the following :
(a) The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?
(b) There were two fixed points in the original Celsius scale as mentioned above which were assigned the number 0°C and 100°C respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) scale?
(c) The absolute temperature (Kelvin scale) T is related to the temperature tc on the Celsius scale byt c = T – 273.15
(d) What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?
(a) The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?
(b) There were two fixed points in the original Celsius scale as mentioned above which were assigned the number 0°C and 100°C respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) scale?
(c) The absolute temperature (Kelvin scale) T is related to the temperature tc on the Celsius scale by
(d) What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?
Solution:
(a) This is because the triple point of water has a unique value i.e. 273.16 K at a unique point, where exists unique values of pressure and volume. On other hand, the melting point of ice and boiling point of water do not have unique set of values as they change with the change in pressure and volume.
(b) The kelvin absolute scales also have the fixed points as the celsius scales have. The other fixed point is absolute zero. It corresponds to the temperature, when the volume and pressure of a gas will become zero.
(c) Triple point of water on celsius scale is 0.01°C and on kelvin scale is 273.16 and the size of degree on the two scale is same, so
t c – 0.01 = T – 273.16
∴ t c = T – 273.15
(d) The unit interval size of Fahrenheit scale is 212 – 32 = 180 divisions
Also we know that the unit interval size of absolute scale is 100.
∴ Triple point of water on an absolute scale having 180 divisions is given by
T =
× 180 = 491.69
(b) The kelvin absolute scales also have the fixed points as the celsius scales have. The other fixed point is absolute zero. It corresponds to the temperature, when the volume and pressure of a gas will become zero.
(c) Triple point of water on celsius scale is 0.01°C and on kelvin scale is 273.16 and the size of degree on the two scale is same, so
(d) The unit interval size of Fahrenheit scale is 212 – 32 = 180 divisions
Also we know that the unit interval size of absolute scale is 100.
∴ Triple point of water on an absolute scale having 180 divisions is given by
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