Understanding the Freezing Point of Water on the Kelvin Scale

The question asks for the freezing point of water as measured on the Kelvin temperature scale. Temperature scales like Celsius, Fahrenheit, and Kelvin are used to quantify how hot or cold something is. Each scale has different reference points, such as the freezing and boiling points of water.

Relating Celsius and Kelvin Temperature Scales

The Celsius scale is commonly used worldwide. On this scale, the freezing point of pure water at standard atmospheric pressure is defined as 0°C, and the boiling point is 100°C.

The Kelvin scale is the standard unit of temperature in the International System of Units (SI). It is an absolute scale, meaning that 0 K (absolute zero) is the point where particles have minimum possible thermal motion. The Kelvin scale uses the same interval size as the Celsius scale; a change of 1 K is equal to a change of 1°C.

The relationship between the Celsius scale (°C) and the Kelvin scale (K) is given by the formula:

\( T(\text{K}) = T(^\circ\text{C}) + 273.15 \)

This formula allows us to convert a temperature from Celsius to Kelvin.

Calculating the Freezing Point in Kelvin

To find the freezing point of water on the Kelvin scale, we use the known freezing point of water on the Celsius scale, which is 0°C.

Using the conversion formula:

\( T(\text{K}) = 0^\circ\text{C} + 273.15 \)

\( T(\text{K}) = 273.15 \text{ K} \)

Therefore, the freezing point of water on the Kelvin scale is 273.15 K.

Analyzing the Options

Let's look at the given options:

• 473.15 K: This temperature is much higher than the freezing point of water. If we convert it to Celsius: \( 473.15 - 273.15 = 200^\circ\text{C} \). This is well above water's boiling point.
• 173.15 K: This temperature is much lower than the freezing point of water. If we convert it to Celsius: \( 173.15 - 273.15 = -100^\circ\text{C} \). This is the freezing point of certain substances, but not water.
• 273.15 K: As calculated, this is the freezing point of water. Converting to Celsius: \( 273.15 - 273.15 = 0^\circ\text{C} \).
• 373.15 K: This temperature corresponds to the boiling point of water on the Kelvin scale. Converting to Celsius: \( 373.15 - 273.15 = 100^\circ\text{C} \).

Based on the conversion and definition, the correct freezing point of water on the Kelvin scale is 273.15 K.

Revision Table: Freezing Point of Water

Additional Information: Temperature Scales and Absolute Zero

The Kelvin scale is particularly important in science because it is an absolute scale. This means that Kelvin temperatures are directly proportional to the thermal energy of a system (under certain conditions, like for ideal gases). Zero Kelvin (0 K), known as absolute zero, is the theoretical temperature at which all molecular motion stops, and a substance has minimum energy. While absolute zero is unattainable in practice, scientists have reached temperatures very close to it. The Celsius scale is a relative scale, where 0°C is just the freezing point of water, not the lowest possible temperature.