Question

samples of four different substances
1 2 3 4
represents a pure substance?
substances 2 and 3
substances 3 and 4
substances 1 and 2
substances 1 and 4

Explanation:

A pure substance has only one type of particle. In the given diagrams, substances 1 and 2 have only one type of particle arrangement (substance 1 has one - type of diatomic molecules, substance 2 has one - type of atoms arranged in a line). Substance 3 has two different types of diatomic molecules, so it is a mixture. Substance 4 has two different types of atoms (assuming different shading or size represents different atoms), so it is also a mixture.

Answer:

substances 1 and 2