A crystalline solid

Options

A. Changes abruptly from solid to liquid when heated
B. Has no definite melting point
C. Undergoes deformation of its geometry easily
D. Has an irregular 3 - dimensional

Answer

**Step-by-Step Solution:**

1. **Understanding Crystalline Solids:**
- A crystalline solid is defined as a solid material whose constituents (atoms, ions, or molecules) are arranged in an orderly repeating pattern extending in all three spatial dimensions.

2. **Melting Point of Crystalline Solids:**
- Crystalline solids have a definite melting point. This means that they transition from solid to liquid at a specific temperature. This is due to their orderly arrangement, which allows them to absorb heat energy until the bonds holding the structure together break at a precise temperature.

3. **Behavior Upon Heating:**
- When heated, the kinetic energy of the particles in a crystalline solid increases. This increase in energy causes the particles to vibrate more vigorously. At the melting point, the energy is sufficient to overcome the forces holding the particles in their fixed positions, leading to a phase change from solid to liquid.

4. **Deformation of Crystalline Solids:**
- Crystalline solids do not undergo deformation easily. They are rigid and maintain their shape until a significant amount of energy (in the form of heat) is applied. Once they melt, they transition into a liquid state, which can flow and change shape.

5. **Irregular Arrangement:**
- The statement regarding an irregular 3D arrangement is incorrect for crystalline solids. Crystalline solids have a regular, repeating arrangement of particles, which distinguishes them from amorphous solids that lack this long-range order.

6. **Conclusion:**
- Based on the properties discussed, the only correct statement regarding crystalline solids is that they change abruptly from solid to liquid when heated. The other statements about having no definite melting point, easily deforming, and having an irregular 3D arrangement are incorrect.

**Final Answer:**
- The correct option is A: Crystalline solids change abruptly from solid to liquid when heated.

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