You are adding heat/energy.
It is melting.
when matter changes state either evolution or absorption of enrgy occurs for example when a solid changes to liquid or a liquid changes to gas energy is absorbed and in case of conversion of gas to liquid or liquid to solid enrgy is liberated....
If we take solid, liquid and gas being the three main states of matter (plasma being an arguable fourth), then from solid to liquid, the process melting occurs, from liquid to gas evaporation or boiling (they are different things) occur. Then from gas to liquid condensation occurs and from liquid to solid freezing occurs.
This change in the state of matter (liquid to solid) is called freezing; it is a physical change, the chemical nature of the molecules is not changed.
The process in which a solid changes to a liquid is called melting.
Liquid to gas, solid to liquid, and liquid to solid
There are several names for when a solid changes to a liquid. Usually, melting of a solid occurs when heat is used near the solid and it changes it to a liquid.
Freezing.
As matter changes from solid to liquid (in other words when solid matter melts) the temperature remains constant. After all the solid has melted, the temperature of the matter may begin to rise again if the environment is warmer than the melting point of the solid.
What type of change occurs when water changes from a solid to a liquid
solid to a liquid
The melting phase changes are Solid~Liquid~Gas and the freezing phase changes are Gas~Liquid~Solid
condensation