Question

Which of the following cannot be classified as a substance

Answer 1

Matter can be categorized as pure substances (elements and compounds) or mixtures (homogeneous and heterogeneous). Salt, pure water, and carbon dioxide are compounds; gold is an element; soil is a heterogeneous mixture; and salt water, pure air, and bronze are homogeneous mixtures.

Step-by-step explanation:

When classifying matter, we categorize it into pure substances and mixtures. A pure substance has a constant composition and properties, while a mixture consists of two or more substances physically combined, presenting variable composition and properties.

Let's classify the following:

• Salt (NaCl) - Compound
• Pure water (H2O) - Compound
• Soil - Heterogeneous mixture
• Salt water - Homogeneous mixture
• Pure air - Homogeneous mixture
• Carbon dioxide (CO2) - Compound
• Gold (Au) - Element
• Bronze - Homogeneous mixture (it's an alloy)

Each of these materials can be identified as an element, a compound, a homogeneous mixture, or a heterogeneous mixture. Elements are fundamental substances that cannot be chemically broken down into simpler substances. Compounds are pure substances composed of two or more elements chemically combined. Homogeneous mixtures have a uniform composition throughout, while heterogeneous mixtures do not.

Answer 2

Gold and nitrogen are elements
Table salt is a compound
Air is a mixture of gases.

I would go with air