why is 0 degress celsius considered both the freezing point of water and melting point of ice?
Zero degrees Celsius is the exact temperature that water begins to freeze and ice begins to melt. Temperatures above 0 will cause ice to melt and below 0 will cause water to freeze.
So then the question becomes:
At 0 degrees Celsius, is water a solid or liquid?
Yes.
Maybe it's slush.
Ms Sue is right. A mixture of ice and water will have a temperature of zero Celsius. If heat is added all of it will melt but the temperature will not rise above zero C until the last bit of ice has melted. If heat is extracted all of it will freeze but the temperature of the mixture will not dip below zero C until the last bit of liquid water has frozen.
Zero degrees Celsius is the temperature at which water freezes and also the temperature at which ice melts. This is because the freezing point and the melting point of a substance are essentially the same temperature.
To understand why this is the case, we need to look at the phase diagram of water. A phase diagram is a graph that shows the different states of a substance (solid, liquid, or gas) at different temperatures and pressures. The phase diagram of water shows a line called the freezing/melting line, which represents the temperatures at which water can exist as both a solid (ice) and a liquid.
At temperatures below zero degrees Celsius, water exists in the solid phase as ice. When heat is applied to ice, its temperature gradually increases. When the temperature reaches zero degrees Celsius, the ice starts to melt, and a phase transition occurs. During this transition, thermal energy is absorbed by the ice, causing the water molecules to gain enough energy to break their bonds and transition from a solid to a liquid state.
Similarly, when water is cooled below zero degrees Celsius, it undergoes a phase transition from liquid to solid, and this temperature is known as the freezing point. At the freezing point, the water molecules lose enough thermal energy to form a solid lattice structure, leading to the formation of ice.
Therefore, zero degrees Celsius is both the freezing point of water and the melting point of ice because it represents the temperature at which water transitions between its solid and liquid phases.