Boiling Point vs Melting Point
Both boiling point and melting point are properties of matter. They play a very important role when it comes to describing material. Boiling point and melting point are characteristics, which arise due to the interaction between the molecules of the particular substance. These interactions are known as intermolecular forces, molecular weights and the shape of molecules of the substance. Applications of melting point and boiling point have a wide range from candle making to pressure cookers. Boiling point and melting point are two phenomena involved in state change of matter.
Boiling point is a property of a liquid. The boiling point is defined as the temperature, where the vapor pressure of the liquid is equal to the external pressure on the liquid. Ideally, a liquid placed at a vacuum space would be at its melting point on zero kelvins (absolute zero). Higher the external pressure higher would be the melting point. This is the simple theory behind pressure cookers. A pressure cooker is a device, where the vapor from the heated water is trapped inside the container. The high amount of vapor inside the container makes external pressure on the liquid higher. This high pressure results a higher boiling point. This method is very useful especially on higher altitudes. Since the atmospheric pressure is lower on higher altitudes, water will boil between 80 0C – 90 0C. This will cause undercooked meals. A liquid boils when it exceeds its saturation temperature at the corresponding saturation pressure. Saturation temperature is defined as the temperature corresponding to the highest thermal energy the liquid can hold without changing its state to vapor at the given pressure. The saturation temperature is also equivalent to the boiling point of the liquid. Boiling occurs when the thermal energy of the liquid is enough to break the intermolecular bonds. The normal boiling point is defined as the saturation temperature at atmospheric pressure. The boiling point varies only between the triple point and the critical point of the liquid.
Melting point is a property of a solid. The melting point is defined as the temperature the solid turns into a liquid. More precisely defined, the melting point is the temperature when the liquid state and the solid state remain in a thermal equilibrium with each other. The melting point and the freezing point of a substance might not be same. For an example, agar melts at 85 0C, but it solidifies back at 31 0C to 40 0C. Intermolecular bonds and molecular weight mostly define the melting point. Some solids like glass don’t have a specific melting point. They simply undergo a smooth transition from solid to liquid.
What is the difference between melting point and boiling point?
– The melting point is a defined for solids when it transfers from solid state to liquid state.
– The boiling point is defined for liquids for a state change from liquid to gas.
– Boiling point is highly dependent on the external pressure whereas the melting point is independent of the external pressure.