Gold is classified as a pure substance. Which of the following properties best supports this classification?

• A. It has a fixed melting point.
• B. It is a good conductor of electricity.
• C. It can be easily shaped into thin sheets.
• D. It has a yellow color.

Answer: (A)

Verified step by step guidance

1. Understand that a pure substance has consistent and uniform properties throughout, including a fixed composition and characteristic physical properties.
2. Recall that one key property of pure substances is having a fixed melting point, which means they change from solid to liquid at a specific temperature without melting over a range.
3. Recognize that properties like electrical conductivity, malleability (ability to be shaped), and color can vary or be shared by mixtures or alloys, so they are not definitive indicators of purity.
4. Identify that the property 'It has a fixed melting point' directly supports the classification of gold as a pure substance because it reflects a consistent and characteristic physical property.
5. Conclude that among the given options, the fixed melting point is the best evidence that gold is a pure substance.