For any pure substance, the boiling point and melting point will always remain the same at a given pressure.

Here's why:

* Melting point: This is the temperature at which a substance changes from a solid to a liquid. It's a specific value for a pure substance because the arrangement of molecules in the solid state is very specific and requires a certain amount of energy to break the bonds and allow the molecules to move freely.

* Boiling point: This is the temperature at which a substance changes from a liquid to a gas. Similar to the melting point, the specific arrangement of molecules in the liquid state and the energy required to overcome the forces holding them together determines the boiling point.

Important Note: The boiling point and melting point can change with pressure. For example, water boils at 100°C at sea level, but at higher altitudes where the atmospheric pressure is lower, it boils at a lower temperature.

Let me know if you'd like more details on how pressure affects boiling and melting points!