Melting: Changing from a Solid to a Liquid

When a substance changes from a solid state to a liquid state, it is said to undergo melting. This phase change occurs when a solid is heated and reaches a specific temperature, known as the melting point. At this point, the solid particles start to gain enough energy to break their fixed positions and move more freely, resulting in the substance changing its state from solid to liquid. Let's understand this process in detail.

1. Solid State: Fixed Arrangement
In its solid state, the particles of a substance are tightly packed and arranged in a regular pattern. They vibrate in place but do not move past each other. This fixed arrangement gives solids their rigid shape and volume.

2. Heat Energy: Increasing Particle Movement
When heat energy is applied to a solid, it causes the particles to gain kinetic energy, which increases their movement. As the temperature rises, the particles vibrate more vigorously, and the solid begins to heat up.

3. Melting Point: Breaking Fixed Positions
Once the solid reaches its melting point, the particles have gained enough energy to overcome the forces holding them in place. At this point, the solid starts to lose its rigid structure, and the particles break their fixed positions.

4. Liquid State: Free Movement
As the solid continues to be heated, the particles gain even more energy, and their movement becomes more chaotic. The bonds between particles weaken, and the substance transforms into a liquid state. In the liquid state, the particles can move past each other, allowing for free movement and the ability to take the shape of their container.

Summary:
When a substance changes from a solid to a liquid, it is undergoing the process of melting. This phase change occurs when the solid reaches its melting point, and the particles gain enough energy to break their fixed positions. The substance transitions from a rigid solid state to a free-flowing liquid state.