Question

Which one of the following is a "substance" in the sense of the word as used in your textbook?

1) air
2) tap water
3) sea water
4) water
5) toothpaste

Answer 1

Sea water is considered a homogeneous mixture due to its uniform composition, whereas toothpaste is classified as a heterogeneous mixture because it has components that are not uniformly distributed.

Step-by-step explanation:

To classify substances as an element, a compound, a homogeneous mixture, or a heterogeneous mixture, we need to understand their composition. An element is a pure substance consisting of only one type of atom. A compound contains two or more different atoms chemically bonded together. A homogeneous mixture, or solution, is a mixture where the components are evenly distributed and cannot be easily separated, such as saltwater.

In the context of this question, sea water would be considered a homogeneous mixture because it consists of water with various dissolved salts, and it presents uniformly throughout. It is also sometimes referred to as a solution. Toothpaste, however, would be considered a heterogeneous mixture because it consists of different substances (abrasives, fluoride, detergents) that are not uniformly distributed and can have varying compositions, which may even be visible to the eye.