Question: What happens to the temperature of an object as it is heated and goes from being a solid to being a liquid and then a gas?
Look at the graph of how the temperature of water changes as we heat it. At the start of heating, the water is in the solid state (ice) and has a temperature of below 0oC. As the ice is heated its temperature rises until it reaches 0oC, which is the melting temperature of ice/water.
When the ice reaches the melting temperature, something unexpected happens. The temperature of the ice does not continue to rise past its melting point despite it still being heated. Instead the temperature of the ice remains at the melting point until all of the ice has melted and become water.
Then the temperature of the water rises steadily from the melting temperature to the boiling temperature. But once the temperature reaches its boiling point, it again stops rising and remain constant at 100oC until all of the water has turned to steam. Once all the water has vaporized the steam's temperature will rise.