Question

pure substance or mixture
part a
matter can be classified as either a pure substance or mixture. pure substances include elements and compounds. review the diagrams of the five samples of matter. which diagram represents a single compound?
part b
matter can be classified as either a pure substance or mixture. air is a mixture of diatomic gases: 21% oxygen and 78% nitrogen. which image could be a model for a mixture like air?

Explanation:

Step1: Recall definitions

A compound is a pure - substance made up of two or more different elements chemically combined. A mixture contains two or more substances that are not chemically combined.

Step2: Analyze diagrams for part A

In diagram I, there are different types of particles (a di - atomic molecule and a mono - atomic particle), so it's a mixture. In diagram II, there are two types of mono - atomic particles, so it's a mixture. In diagram III, all particles are the same type of di - atomic molecule (same two - element combination), so it represents a single compound. In diagram IV, there are two types of di - atomic molecules, so it's a mixture. In diagram V, it's a single element (mono - atomic).

Step3: Analyze diagrams for part B

Air is a mixture of different gases. Diagram I has different types of particles (a di - atomic and a mono - atomic), which can represent a mixture like air. Diagram II has only mono - atomic particles of two types, but air has di - atomic gases mainly. Diagram III is a single compound. Diagram IV has only di - atomic particles of two types but not a good representation of air's composition.

Answer:

PART A: D. III
PART B: A. I