Water freezes at :

Question

Water freezes at :

Accepted Answer

The correct option is 1:

The correct option is 1 (0°C):
In standard scientific terms, the freezing point of pure water at standard atmospheric pressure (1 atmosphere or 101.325 kPa) is 0 degrees Celsius (0°C). Freezing is the process where a liquid substance changes its phase into a solid, often called its freezing point. This temperature is a fundamental reference point for the Celsius scale, alongside 100°C, which is the boiling point of water. It is the temperature at which the kinetic energy of water molecules decreases to the point where they arrange themselves into a rigid, crystalline structure known as ice.

The incorrect option is 2 (5°C):
The temperature 5°C is well above the freezing point of water. At this temperature, water exists naturally in its liquid state under standard pressure. While water is certainly cold at 5°C, the molecules still possess enough kinetic energy to move freely past one another, preventing the formation of a stable, crystalline solid structure. This temperature is typically found in cold environments, but it is not cold enough to initiate the phase transition from liquid water to solid ice.

The incorrect option is 3 (15°C):
15°C represents a cool but generally moderate or room temperature environment. Water at 15°C is entirely in its liquid phase and would not begin to solidify. In many regions, this is considered a comfortable temperature for a cold drink or tap water. The energy level of water molecules at 15°C is much too high to allow for the orderly arrangement required for freezing to occur.

The incorrect option is 4 (100°C):
The temperature 100°C is the standard boiling point of pure water at sea level, not its freezing point. At 100°C, water absorbs heat energy until it transitions from a liquid state to a gaseous state (steam). This is the exact opposite of freezing, which is an exothermic process (releasing heat). At this high temperature, the water molecules are moving rapidly and overcoming the intermolecular forces that hold them together as a liquid.