In basic temperature scales, the normal melting point of pure ice at standard atmospheric pressure is ______ K (Kelvin).

Introduction / Context:
The melting point of ice is a very common fact in general science and chemistry and is used while converting between the Celsius and Kelvin temperature scales. Many competitive exams like to test whether students remember the numerical value of this temperature in Kelvin, because it also reinforces the idea that the Kelvin scale starts at absolute zero and shifts the Celsius scale by a fixed amount.

Given Data / Assumptions:

• We are considering pure ice made of water, not mixtures or impure samples.
• The pressure is standard atmospheric pressure (about 1 atm), which is the usual reference condition.
• On the Celsius scale, the normal melting point of ice is 0 degree Celsius.
• The Kelvin scale is related to the Celsius scale by the relation K = degree Celsius + 273.16 (approximately).

Concept / Approach:
To express the melting point of ice in Kelvin, we use the linear relationship between the Celsius and Kelvin scales. The Kelvin scale starts at absolute zero, while the Celsius scale is set so that 0 degree Celsius corresponds to the melting point of ice under standard pressure. Since the offset between the two scales is about 273.16, the temperature 0 degree Celsius is equivalent to 273.16 K. Remembering this key conversion allows you to quickly move between Celsius and Kelvin for many basic temperature values.

Step-by-Step Solution:
Step 1: Recall that the normal melting point of ice is 0 degree Celsius. Step 2: Use the formula K = degree Celsius + 273.16 for the approximate conversion between Celsius and Kelvin at this precision. Step 3: Substitute degree Celsius = 0 into the expression: K = 0 + 273.16. Step 4: This gives the Kelvin temperature as 273.16 K. Step 5: Compare this value with the options and select 273.16 as the correct numerical answer.

Verification / Alternative check:
Textbooks often quote the relation between Celsius and Kelvin as K = degree Celsius + 273 or K = degree Celsius + 273.15 or 273.16, depending on the level of accuracy. For rough work, 273 is acceptable, but in many theory based questions the slightly more precise 273.16 is used. In any case, the melting point of ice in Kelvin is always near 273 K, not near 253 K, 263 K, 283 K, or room temperature around 293 K. This numerical consistency check confirms that 273.16 K is the physically sensible choice.

Why Other Options Are Wrong:
- 253.16: This would correspond to about minus 20 degree Celsius, which is below the melting point of ice and would represent ice that is still solid, not melting under normal conditions.
- 263.16: This equals about minus 10 degree Celsius, also below the melting point and still too cold for ice to melt at 1 atm pressure.
- 283.16: This is about 10 degree Celsius, which is above the melting point and represents liquid water that is clearly warmer than the freezing point.
- 293.16: This is about 20 degree Celsius, close to comfortable room temperature, far above the temperature at which ice begins to melt.

Common Pitfalls:
Students may confuse the freezing point of water, the boiling point of water, and common room temperature when converting to Kelvin. Another frequent error is to add or subtract the offset in the wrong direction, for example writing 0 degree Celsius as 273.16 degree Celsius instead of 273.16 K. Keeping the simple rule K = degree Celsius + 273 (approximately) in mind helps avoid such mistakes and allows quick checking of rough temperature values.

Final Answer:
The normal melting point of pure ice at standard atmospheric pressure is 273.16 K.