Solid Properties Explained by Particle Arrangement

The question asks which property best explains why solids maintain a definite shape and volume.

Particle Arrangement in Solids

The behavior of matter at the macroscopic level (like shape and volume) is determined by how its constituent particles (atoms, molecules, or ions) behave at the microscopic level.

• Definite Shape & Volume: Solids are characterized by their fixed shape and volume.
• Particle Behavior: This requires the particles to be held in specific positions.

Analyzing the Options

• Option 1: Particles move freely. This describes liquids or gases, where particles have enough energy to overcome attractive forces and move past each other, resulting in indefinite shape and/or volume.
• Option 2: Large spaces between particles. This is characteristic of gases, where particles are far apart and move randomly, leading to compressibility and indefinite shape and volume.
• Option 3: Particles are closely packed in a fixed arrangement. This arrangement means the particles have strong attractive forces holding them in place. They can vibrate but cannot move freely past each other. This restricted movement and proximity directly result in the definite shape and volume observed in solids.

Conclusion

The property that directly explains why solids have a definite shape and volume is the way their particles are arranged. Specifically, being closely packed in a fixed arrangement restricts particle movement, thus maintaining the solid's form and size.