When measuring a melting point why is it necessary to raise the temperature very slowly when approaching a melting temperature?

You warm the soil slowly to ensure that the solid is same temperature throughout (isothermal). If you warmed it too quickly, the part closest to the heater would melt, while the part with the thermometer in it would still be a solid, and so you would have the wrong value for the melting point.

Ok so co(g) is not pronoused that. the only clue is that youpronouse it the oppisote way. 

What are the options? physical property can be color, smell, opacity, viscosity, density, infra red spectrum, melting and boiling points, attraction and repulson to magnets, etc.