Melting and Freezing Point – Introduction and Explanation

Melting and Freezing Point 

Introduction

Melting point is a characteristic property of solid crystalline substances. Melting point is the temperature at which the solid changes to the liquid. Melting point determines the characteristic nature of solid crystal.  

The stronger the forces of attraction between the particles, the more energy is needed to overcome them. That more energy is provided by external sources such as heat. This more energy is used to heat the substance at higher temperature, which leads to high melting point. 

Explanation

What is melting and melting point? 

Melting is the process by which a solid change to a liquid upon heating. The point at which a solid change its state to a liquid is called the melting point. 

As heat is applied to the solid substance, the temperature increases and remains constant until the solid state converts to liquid. 

The melting temperature of crystalline solids may be a characteristic figure and is employed to spot pure compounds and elements. Most mixtures and amorphous solids melt over a variety of temperatures. 

Solid, a pure substance features a characteristic freezing point, the temperature at which the solid melts to become a liquid.  

However, substances are often cooled below their freezing points without the formation of a solid. Such liquids are referred to as supercooled liquids. 

Example: The freezing point of sugar (sucrose) is 186°C (295°F), and the freezing point of salt is 801°C (1,474°F). 

For characterizing a substance, its freezing point is preferred. The melting temperature of a substance in its solid state is usually considered to be equivalent to its freezing temperature, because the melting point corresponds to the liquid state of a substance. A liquid may freeze in several crystal system because impurities lower the melting point, however, the particular freezing point might not be equivalent to the substance’s melting point. The melting point of the ice is 0^oC and freezing point of the water is 0^oC 

What happens to the melting point if impurities are added? 

The presence of impurities in a substance leads to a lower freezing point, this process is called freezing point depression. Freezing point depression is the reason why adding salt to frozen substances help to melt the ice. Freezing point depression occurs to the character of a material’s solid state. 

Uses: 

Melting point is used in research and even used for the development of quality in industries to identify the solid crystals present in the substance and it is used to check their purity. 

Examples: 

Activity-1 

1. Take an ice cube and pour it in an empty glass.  

2. Leave it for some time. 

3. Later the ice cube turns into water, this is due to the temperature or heat percentage present in the atmosphere. 

4. On adding heat or increasing the temperature, solid turns to liquid. 

5. This defines that ice cube melts into water. 

Activity-2 

1. Take a solid butter and a pan. 

2. Now place the pan on the stove and light the stove. 

3. Add some solid butter to the heated pan.  

4. Now as the heat or temperature increases slowly, the solid gets converted to liquid. 

5. So, slowly solid butter gets turned into liquid. 

6. This is an example of melting.