What are the freezing point and boiling point of water on the Celsius scale?
The correct answer and explanation is:
The freezing point of water on the Celsius scale is 0°C, and the boiling point is 100°C at standard atmospheric pressure (1 atmosphere or 101.3 kPa).
Freezing Point of Water
The freezing point is the temperature at which a liquid turns into a solid. For water, this occurs at 0°C under normal atmospheric conditions. As water cools, its molecules slow down and arrange themselves into a crystalline structure, forming ice. This phase change from liquid to solid happens when the temperature of water reaches this point, and it is considered the reference for the Celsius scale.
Boiling Point of Water
The boiling point is the temperature at which a liquid turns into a gas. For water, this occurs at 100°C at standard atmospheric pressure (1 atmosphere). When water is heated, its molecules gain energy and move faster. As the temperature increases, the water molecules eventually gain enough energy to overcome the attractive forces between them and transition into the gas phase, forming steam. This phase change from liquid to gas happens at the boiling point.
It is important to note that both the freezing and boiling points can change with changes in atmospheric pressure. For example, at higher altitudes, the atmospheric pressure is lower, so the boiling point of water decreases. Similarly, if the pressure is increased, like in a pressure cooker, the boiling point of water will increase. This explains why water can boil at temperatures lower than 100°C at high elevations and higher than 100°C in pressure cookers.
The Celsius scale is based on these two key points, with 0°C as the freezing point and 100°C as the boiling point, making it convenient for everyday use in measuring temperatures for weather, cooking, and science.