1. Increased Energy: The molecules in a solid are tightly packed and vibrate in fixed positions. When heat is applied, the molecules absorb energy and start to vibrate faster.
2. Weakening Bonds: As the molecules vibrate more vigorously, the bonds holding them together weaken. These bonds are the forces that keep the molecules in a fixed, rigid structure.
3. Increased Distance: With weaker bonds, the molecules begin to move further apart, breaking free from their rigid positions. They start to flow and slide past each other.
4. Change in State: When enough energy is absorbed, the molecules have enough freedom to move around freely. The substance has now transitioned from a solid state to a liquid state.
Key Points:
* Melting Point: Each substance has a specific temperature at which it melts, called the melting point.
* Heat of Fusion: Energy is required to break the bonds holding the solid together. This energy is called the heat of fusion.
* Reversibility: The process of melting is reversible. When the liquid cools down, it solidifies again.
Example:
Imagine an ice cube (solid water). When you apply heat, the molecules in the ice start vibrating more vigorously. The bonds between the water molecules weaken, and the ice melts into liquid water.
