Which of the following is a pure substance?

Granite is a natural rock composed of various minerals such as quartz, feldspar, and mica, each contributing to its overall structure and appearance. This mixture of different substances means that granite does not have a uniform composition, making it a heterogeneous mixture rather than a pure substance.

Toothpaste contains a combination of various ingredients, including abrasives, fluoride, flavoring agents, and humectants, which work together for dental hygiene. Because it is a mixture of multiple compounds and does not have a consistent composition throughout, toothpaste is not classified as a pure substance.

Sugar water is a solution formed by dissolving sugar (sucrose) in water. While sugar may be a pure substance, the combination with water creates a mixture that can vary in concentration depending on the amount of sugar dissolved. Therefore, sugar water, as a solution of two materials, does not meet the criteria for a pure substance.