Solids, liquids and gases can be compared in terms of how far apart their particles are, on average. Which list puts the three states of matter in order of increasing average particle separation, from smallest to largest?

Answer: C. Step 1: Recall the particle arrangement in each state - In a solid, particles are held closely together in a regular, fixed arrangement, vibrating about fixed positions. - In a liquid, particles are still close together (only slightly furt…

IGCSE Physics 0625: Comparing Particle Separation in Solids, Liquids and Gases

Step 1: Recall the particle arrangement in each state

In a solid, particles are held closely together in a regular, fixed arrangement, vibrating about fixed positions.
In a liquid, particles are still close together (only slightly further apart than in a solid) but are free to move and slide past one another.
In a gas, particles are, on average, very far apart compared with their own size, and move quickly and randomly, filling any container they are placed in.

Step 2: Compare the three separations

Going from solid to liquid, the average separation increases only a little. The particles are still touching or nearly touching. Going from liquid to gas, the average separation increases enormously, since gas particles have large empty spaces between them.

So the correct order of increasing average separation is:

$\text{solid} < \text{liquid} < \text{gas}$

Step 3: Match to the options

This order (solid, liquid, gas) is option C.

Why the other options are wrong

Option	Order given	Error
A	gas, liquid, solid	This is the reverse order (decreasing separation), not increasing.
B	liquid, solid, gas	Incorrectly places liquid before solid.
D	solid, gas, liquid	Incorrectly places gas before liquid.

Final answers

Order of increasing particle separation: solid, liquid, gas, option C.