Question

At 1 atm, an unknown sample melts at 57.9 °C and boils at 109.5 °C. If the temperature is 57.9°C, what is the state of matter for the sample?

Answer 1

Melting point is a temperature at which is substance is in equilibrium with its solid and liquid phase. Here melting point of sample is given 57.9 degree Celsius so we can say that sample will be in solid and liquid phase. But if we supply latent heat of fusion then simple in solid phase will transform into liquid phase.

So if sample is kept at 57.9 degree Celsius which is melting point , then sample will be in equilibrium of solid and liquid phase means both phase will exist (solid and liquid).