Liquid nitrogen is used in cryosurgery for wart removal (N₂ liquefies at −196 °C and freezes at −210 °C). Which temperature range coincides with the condensation of N₂ gas?

Question

Quizplus · Accepted Answer

11ecba2d_11fc_8886_a3bf_db09131842a2_MD0008_00 The Kelvin scale differs from the Celsius scale only in the placement of the zero value. The Celsius scale defines the zero value with respect to the freezing point of water whereas the Kelvin scale moves the zero value to be defined with respect to absolute zero (−273.15 °C), which is the coldest temperature theoretically possible. Accordingly, 0 K = −273.15 °C, and the Kelvin scale is considered an absolute temperature scale because it has no negative values. Because the size of the units are the same on both the Celsius and the Kelvin scales and the scales differ only by the placement of the zero value, a change of 1 degree Celsius is equal to a change of 1 Kelvin. As a result, a temperature given in degrees Celsius can be converted to its equivalent on the Kelvin scale by adding 273.15 (often rounded to just 273). Similarly, the conversion of Kelvin temperatures to degrees Celsius is done by subtracting 273.15 from the Kelvin temperature. Nitrogen gas (N₂) condenses near −196 °C. On the Kelvin scale, this value is found to be Kelvin = (°C + 273) = (−196 °C + 273) = 77 K Therefore, a temperature range of 75-79 K coincides with the temperature at which N₂ liquefies. (Choice A) N₂ freezes at −210 °C (63 K). A temperature range of 61-65 K coincides with the freezing point of N₂ rather than the condensation of N₂. (Choices C and D) Conversion of temperatures in Celsius to the Kelvin scale requires adding 273 to the Celsius values. If the temperatures −196 °C and −210 °C are instead subtracted from 273, erroneous values of 469 K and 483 K, respectively, are obtained. Educational objective: The Kelvin and Celsius scales differ only in the placement of the zero value. Therefore, a change of 1 degree Celsius is equal to the change of 1 Kelvin. A temperature on the Celsius scale can be converted to its equivalent on the absolute Kelvin scale by adding 273.15 to the Celsius temperature.

Liquid Nitrogen Is Used in Cryosurgery for Wart Removal (N2

Liquid Nitrogen Is Used in Cryosurgery for Wart Removal (N₂