Melting: When a solid changes into a liquid

Introduction:
When a substance changes its state from solid to liquid, it undergoes a process called melting. This process is characterized by the absorption of heat energy, which causes the particles in the solid to gain enough energy to overcome the forces holding them in a fixed position and start moving more freely.

Explanation:
Melting is a phase transition process in which a solid substance changes into a liquid state. This occurs when the temperature of the substance reaches its melting point, also known as the freezing point in the reverse process. During melting, the arrangement of particles in the solid lattice structure changes, allowing the substance to flow and take the shape of its container.

Key points:
Here are some key points to remember about the process of melting:

1. Heat Energy Absorption: Melting requires the absorption of heat energy from the surroundings. This energy is used to break the bonds between the particles in the solid and convert them into a liquid state.

2. Melting Point: Every substance has a specific temperature at which it melts. This temperature is known as the melting point. For example, the melting point of ice is 0 degrees Celsius, while the melting point of iron is 1538 degrees Celsius.

3. Particle Movement: As the solid is heated, the particles gain kinetic energy and start vibrating more vigorously. At the melting point, this vibration becomes strong enough to overcome the attractive forces between particles, allowing them to move more freely.

4. Molecular Arrangement: In the solid state, the particles are closely packed in a regular pattern. During melting, the arrangement of particles changes, and they become less closely packed, resulting in a decrease in density.

5. Reversible Process: Melting is a reversible process, meaning that the substance can be converted back into a solid state through the process of freezing. When the liquid is cooled below its melting point, the particles lose energy, slow down, and reorganize into a solid lattice structure.

Conclusion:
In summary, melting is the process by which a solid substance changes into a liquid state. It involves the absorption of heat energy, particle movement, and rearrangement of the particle structure. Understanding the concept of melting helps us comprehend various natural phenomena and industrial processes involving phase changes.