The Melting point and Freezing point are both temperatures at which one state gets the change to another state. The actual compound at these temperatures gets converted into a different compound. The temperature defines which state will form into which state. A pure substance has a particular temperature at which the substance will attain its melting and freezing point.
Melting Point vs Freezing Point
The main difference between Melting Point and Freezing Point is Melting point occurs when the state of the substance changes from solid to liquid, but the Freezing point occurs when the liquid is changing into a solid when the heat of the substance is taken out. The melting point can be observed when temperature increases, and Freezing Point can be observed when temperature decreases.
Melting point occurs when the substance undergoes a change in its state and turns solid to liquid. Heat is given to the substance. As the temperature rises in the solid, it starts melting, and at a temperature, it fully gets converted into the liquid
The Freezing point occurs when the substance undergoes changes and gets converted from liquid to solid. When the temperature decreases in the liquid, it starts forming solid. It completely forms solid when it reaches its freezing point. The substance freezes and melts at the same temperature.
Comparison Table Between Melting and Freezing Point
| Parameters of Comparison | Melting Point | Freezing Point |
| Definition | Solid turns liquid at a particular temperature. | Liquid changes to solid at a particular temperature |
| Process | The process is called melting. | The process is called freezing. |
| Heat | Supplied from external sources | Taken away from the substance |
| Volume | Increases | Decreases |
| Internal Energy | Increases | Decreases |
| Examples | Solid to liquid wax | Water turns ice |
What is Melting Point?
Melting point occurs when the substance undergoes a change in its state and turns solid to liquid. The melting point of the crystalline compounds defines pure compounds and elements of the solid. External sources are required to give heat to the solid so that the heat will raise the temperature of the solid and finally turns into liquid.
It is a physical change. It is reversible. During heating, the volume of the substance increases. The Melting point of the crystalline compounds defines pure compounds and elements of the solid. The internal energy of the solid keeps on increasing when the solid gets heated.
A pure substance has a particular temperature at which the substance will attain its melting and freezing point. The impurity in the substance affects its melting and freezing temperature. The molecules move more when the temperature rises.
This is a great idea to use the melting point as an indication to know to how much extent the substance is pure. The external pressure is one of the factors why the substance reaches its melting point. Crystalline compounds have a constant melting point.
The substance can be declared very pure when the substance attains its melting point at just 0.1 degrees celsius. The transition from solid to liquid is so low. An example of a Melting point is solid oxygen has a melting point at -218.4 degrees celsius.
What is Freezing Point?
The Freezing point occurs when the substance undergoes changes and gets converted from liquid to solid. When the heat of the solid is taken away, the heat inside the solid keeps on decreasing, which results in the solid change into a liquid.
When the temperature decreases in the liquid, it starts forming solid. It completely forms solid when it reaches its freezing point. The substance freezes and melts at the same temperature. It is a physical process. It is a reversible process.
The volume of the solid material decreases in this procedure. The internal energy of the solid is affected and decreases. This change occurs in a high state energy state and then moves to lower state energy. The molecules have to move less due to a decrease in their temperature.
In this, the molecules are becoming ordered and taking a fixed shape as the temperature is decreasing. It has less freedom of movement as it is reaching its freezing point. The pressure is increased in the liquid to make it solid. The impurity in the substance minimizes the freezing point. This is a good indication of purity. The purity in the substance can be defined using a freezing point.
Main Differences Between Melting and Freezing Point
- Melting point occurs when the substance undergoes a change in its state and turns solid to a liquid, but the Freezing point occurs when the substance undergoes changes and gets converted from liquid to solid.
- Atmospheric pressure is a major factor of melting point, but external pressure is a major factor of freezing point.
- Melting point occurs when heat is supplied to the solid, whereas the heat is sucked out to reach the Freezing point.
- The volume of the solid increases when the solid is reaching the Melting point but the volume of the liquid decreases when the liquid reaches the Freezing point.
- The Melting point increases the internal energy, but the Freezing point decreases the internal energy.
Conclusion
Melting point occurs when the substance undergoes a change in its state and turns solid to liquid. Heat is given to the substance as the temperature rises in the solid, it starts melting, and at a temperature, it fully gets converted into the liquid at a particular temperature termed as the melting point.
Crystalline compounds use a melting point to define pure compounds and elements of the solid. When the heat of the solid is taken away, the heat inside the solid keeps on decreasing, which results from the solid change into a liquid.
When the temperature decreases in the liquid, it starts forming solid. It completely forms solid when it reaches its freezing point. The substance freezes and melts at the same temperature. It is a physical process. It is a reversible process.
The volume of the solid gets decreased in this process. The internal energy of the solid is affected and decreases. During heating, the volume of the substance increases. The internal energy of the solid keeps on increasing when the solid gets heated.
A pure substance has a particular temperature at which the substance will attain its melting and freezing point. The impurity in the substance affects its melting and freezing temperature. The molecules move more when the temperature rises. Crystalline compounds have a constant melting point.
References
- https://www.sciencedirect.com/science/article/pii/S0095852248900488
- https://www.sciencedirect.com/science/article/pii/S0378775306015886