What happens to water below 0°C at standard atmospheric pressure?

• A. It evaporates
• B. It becomes steam
• C. It remains a liquid
• D. It freezes into ice

Answer: (D)

When water is exposed to temperatures below 0°C at standard atmospheric pressure, it undergoes a phase change from liquid to solid. This solid state of water is known as ice. The process is called freezing, where the molecules of water lose energy and arrange themselves into a more stable and fixed structure, which is the crystalline form of ice.

At 0°C, water is at its freezing point, meaning that any further decrease in temperature will facilitate more molecules transitioning into the solid state. In contrast, above 0°C, water remains in its liquid state due to higher energy levels that prevent solidification. Thus, at temperatures below the freezing point, water will consistently solidify into ice unless other conditions, such as changes in pressure or the presence of impurities, come into play.