The melting point of a substance is the temperature at which it transitions from a solid to a liquid, as it absorbs heat. At the melting point, the solid’s molecules gain enough energy to overcome the forces holding them in the rigid structure, allowing the substance to melt and become a liquid.
The melting point is a characteristic property of the substance, and like other phase transitions, it can depend on the surrounding pressure.
Examples:
- Ice (Water):
- Melting Point: 0°C (32°F) When ice is heated to 0°C, it melts into liquid water. This is the point at which solid water (ice) becomes liquid water.
- Gold:
- Melting Point: 1,064°C (1,947°F) Gold has a much higher melting point compared to water, meaning it requires much more heat to melt.
- Iron:
- Melting Point: 1,538°C (2,800°F) Iron melts at a very high temperature, which is why it is commonly used for high-temperature applications like in metal casting.
- Ethanol (Alcohol):
- Melting Point: -114.1°C (-173.4°F) Ethanol is a liquid at most temperatures on Earth, as its melting point is much lower than water’s, making it useful in applications like antifreeze.
- Butter:
- Melting Point: 30–35°C (86–95°F) Butter, a mixture of fats, melts at relatively low temperatures, which is why it becomes soft or liquid when left out at room temperature.
Key Notes:
- The melting point of pure substances is typically a fixed temperature, but mixtures (like alloys) can have a range of melting points.
- The melting point can be influenced by impurities in the substance, often causing a lower melting point in impure substances compared to the pure form.
In summary, the melting point is the temperature at which a substance changes from a solid to a liquid, and it varies widely depending on the material.