The temperature of liquid nitrogen is -196 C. What is the corresponding reading on the Kelvin scale?
A. 77K
B. -127 K
C. -91 K
D. 48 K
E. 146 K
The Correct Answer and Explanation is:
To convert from degrees Celsius (°C) to Kelvin (K), you use the formula:
$$
K = °C + 273.15
$$
Given:
$$
°C = -196
$$
Substitute into the formula:
$$
K = -196 + 273.15 = 77.15
$$
Rounded to the nearest whole number, the temperature is 77 K.
Correct Answer: A. 77K
Temperature is a measure of the average kinetic energy of particles in a substance. The Celsius and Kelvin scales are both used to measure temperature, but they have different starting points. The Celsius scale is based on the freezing (0°C) and boiling (100°C) points of water at standard atmospheric pressure, while the Kelvin scale is an absolute temperature scale used in science.
The Kelvin scale starts at absolute zero (0 K) — the theoretical point at which particles have minimum possible thermal motion. This is equivalent to -273.15°C. Unlike Celsius or Fahrenheit, the Kelvin scale does not use degrees, just “Kelvin” (K).
To convert from Celsius to Kelvin, you add 273.15. This is because 0°C is equal to 273.15 K. So, for any temperature in Celsius:
$$
\text{Kelvin} = \text{Celsius} + 273.15
$$
Liquid nitrogen is commonly used as a cryogenic coolant and has a boiling point of -196°C. When we convert this to Kelvin:
$$
-196 + 273.15 = 77.15\, \text{K}
$$
This value, when rounded to the nearest whole number, gives us 77 K. This places liquid nitrogen well below the freezing point of water, explaining its ability to rapidly freeze materials upon contact.
Among the provided options:
- A. 77K is the correct and scientifically accurate answer.
- The other choices are incorrect and do not align with the proper conversion from Celsius to Kelvin.
Therefore, Option A is correct.
