Particles expand in states of decreasing density

Steps:

• Identify changes where particle spacing increases, such as melting or gas expansion.
• Change 1: Solid to liquid (melting) – particles gain energy, vibrate more, move slightly apart.
• Change 4: Liquid to gas (boiling) – particles escape bonds, spread far apart in vapor.
• Changes 2 and 3 involve contraction or denser packing, so particles move closer.

Why B is correct:

• B pairs changes 1 and 4, matching phase transitions where intermolecular forces weaken, increasing average distance per kinetic molecular theory.

Why the others are wrong:

• A includes 2 (likely freezing, particles pack tighter).
• C includes 2 and 3 (both condensation-like, reducing spacing).
• D includes 3 (deposition, particles form solid lattice, closer together).

Not enough information on exact changes 1–4, but based on standard examples, B fits.

Final answer: B