Know the distinguishing properties of solids, liquids and gases

2.1.1 States of Matter

Objective

Know the distinguishing properties of solids, liquids and gases.

Key Concepts

• Shape and volume
• Particle arrangement and motion
• Compressibility
• Diffusion and effusion
• Density and intermolecular forces

Properties of Solids

Solids have a definite shape and a definite volume. The particles are closely packed in a regular pattern and vibrate about fixed positions.

• Shape: Definite
• Volume: Definite
• Particle arrangement: Ordered, fixed positions
• Particle motion: Vibrational
• Compressibility: Very low
• Diffusion: Negligible
• Density: Generally high

Properties of Liquids

Liquids have a definite volume but take the shape of their container. Particles are close together but not in a fixed pattern, allowing them to slide past one another.

• Shape: Takes shape of container
• Volume: Definite
• Particle arrangement: Disordered, close‑packed
• Particle motion: Translational and rotational
• Compressibility: Low
• Diffusion: Moderate (e.g., mixing of liquids)
• Density: Usually lower than solids but higher than gases

Properties of Gases

Gases have neither a definite shape nor a definite volume. Their particles are far apart and move rapidly in all directions.

• Shape: Takes shape of container
• Volume: Takes volume of container
• Particle arrangement: Very dispersed
• Particle motion: Random, high‑speed translational motion
• Compressibility: High
• Diffusion: Rapid (e.g., perfume spreading)
• Density: Very low

Comparison Table

Relevant Equations

For gases, the ideal‑gas equation relates pressure, volume, temperature and amount of substance:

\$pV = nRT\$

where \$p\$ is pressure, \$V\$ is volume, \$n\$ is the number of moles, \$R\$ is the universal gas constant and \$T\$ is absolute temperature.