Which of the following would you characterize as pure or nearly pure substance? (a) stomach acid; (b) dry ice; (c) ice-cream; (d) stainless steel; (e) petroleum; (f) distilled water; (g) carbon monoxide gas; (h) compressed air in balloon.

Verified step by step guidance

1. Identify the definition of a pure substance: A pure substance consists of only one type of element or compound, with a uniform and definite composition.
2. Analyze each option to determine if it is a pure substance: (a) Stomach acid is a mixture of hydrochloric acid and other substances, so it is not pure.
3. (b) Dry ice is solid carbon dioxide (CO₂), which is a compound, making it a pure substance.
4. (c) Ice-cream is a mixture of various ingredients, so it is not a pure substance.
5. (d) Stainless steel is an alloy, which is a mixture of metals, so it is not a pure substance.
6. (e) Petroleum is a complex mixture of hydrocarbons, so it is not a pure substance.
7. (f) Distilled water is pure H₂O, making it a pure substance.
8. (g) Carbon monoxide gas is a compound (CO), making it a pure substance.
9. (h) Compressed air in a balloon is a mixture of gases, so it is not a pure substance.
10. Summarize the pure substances identified: Dry ice (b), distilled water (f), and carbon monoxide gas (g) are pure substances.

Key Concepts

Pure Substances vs. Mixtures

A pure substance consists of a single type of particle and has a uniform composition and distinct properties. In contrast, mixtures contain two or more different substances that retain their individual properties. Understanding this distinction is crucial for identifying which options in the question are pure substances.

Chemical Composition

The chemical composition of a substance refers to the types and ratios of atoms that make it up. For example, distilled water (H2O) is a pure substance with a specific chemical formula, while mixtures like ice cream contain various components that can vary in proportion. Recognizing the chemical composition helps in determining purity.

State of Matter

The state of matter (solid, liquid, gas) can influence whether a substance is considered pure. For instance, dry ice (solid CO2) and carbon monoxide gas (CO) are both pure substances in their respective states. Understanding the state of matter aids in evaluating the options presented in the question.