Pure Substances

Question

Matter can be categorized into one of two groups: pure substances and mixtures. Pure substances are made of either one kind of atom or one kind of molecule or compound. A pure substance that is composed of one kind of atom is called an element. Pure carbon, pure gold, and pure oxygen are all elements.

Heterogeneous Mixtures
Most of the materials we interact with every day are not pure substances. Remember that a material composed of more than one pure substance is called a mixture. Mixtures are divided into two categories: heterogeneous and homogeneous.

Homogeneous Mixtures
The other type of mixture is homogenous mixture. The prefix homogene– means “of the same” in Latin. In a homogeneous mixture, the ratio of each compound to the others is the same everywhere in the mixture. In other words, the mixture is uniform. For example, if you were to mix table sugar in warm water and stir it well, you might find when you tested the mixture that the ratio of sugar to water in the top of the glass is the same ratio as in the bottom of the glass. A glass of sugar water would, therefore, be a homogeneous mixture. Other examples include toothpaste, pennies, and most types of gold jewelry.

Answer 1

Your summary of pure substances and mixtures clearly delineates the differences between various categories of matter. Here’s a concise recap of the key points:

Pure Substances

• Definition: Matter made of one kind of atom or molecule/compound.
• Types:
  • Elements: Pure substances with only one type of atom (e.g., carbon, gold, oxygen).

Mixtures

• Definition: Combinations of two or more pure substances.
• Types:
  • Heterogeneous Mixtures: Composition varies throughout the mixture. Different components are easily distinguishable (e.g., salad, sand and iron filings).
  • Homogeneous Mixtures: Uniform composition throughout. The ratio of compounds is the same regardless of where you sample (e.g., sugar water, air, alloys).

This organization helps to understand the fundamental categories of matter and their properties in both pure and mixed forms. If you need further details on any aspect or additional examples, feel free to ask!