Classify each of the following as a pure substance, a solution, or a heterogeneous mixture: (a) a leaf (b) a 999 gold bar

Verified step by step guidance

1. Understand the definitions: A pure substance has a uniform and definite composition, a solution is a homogeneous mixture of two or more substances, and a heterogeneous mixture has a non-uniform composition.
2. Consider the composition of a 999 gold bar: It is composed of 99.9% gold, with the remaining 0.1% typically being other metals or impurities.
3. Evaluate the uniformity: Since the gold bar is mostly gold with very little impurity, it has a uniform composition throughout.
4. Determine the classification: A 999 gold bar is considered a pure substance because it is primarily composed of one element, gold, with minimal impurities.
5. Conclude: Based on its composition and uniformity, classify the 999 gold bar as a pure substance.

Key Concepts

Pure Substance

A pure substance consists of a single type of particle and has a uniform composition and properties throughout. Examples include elements like gold and compounds like water. Pure substances cannot be separated into simpler substances by physical means.

Heterogeneous Mixture

A heterogeneous mixture contains two or more phases or components that are not uniformly distributed. The individual components can often be seen and separated physically, such as in a salad or a mixture of sand and salt. The properties of heterogeneous mixtures vary throughout the sample.

Solution

A solution is a homogeneous mixture where one substance (the solute) is dissolved in another (the solvent). Solutions have a consistent composition and properties throughout, such as saltwater or sugar dissolved in tea. Unlike heterogeneous mixtures, solutions do not have visibly distinct components.