Question

Identify whether the given description is about a mixture or a "pure substance."

1. It is made up of elements in fixed proportions.
2. The components can be readily separated, e.g. by filtratioor distillation.
3. The boiling point changes (rises) as the substance boilsaway in distillation.
4. It is very difficult to separate the components of the substance.
5. The elements or compounds are not in fixed proportions.
6. The substance melts or boils at a specific temperature.
7. The substance melts gradually over a few degreestemperature range.
8. There is no significant energy change on its formation​.

Answer 1

A pure substance has fixed proportions and a specific melting or boiling point, while a mixture contains components in variable proportions and can often be separated by physical means.

Step-by-step explanation:

When assessing if a given description is about a pure substance or a mixture, one must consider various characteristics. A pure substance includes elements and compounds, has fixed proportions, and typically has a sharp melting or boiling point. In contrast, a mixture does not have fixed proportions and may show a range of boiling or melting points as it consists of two or more substances that can often be separated through physical means such as distillation or filtration.

Descriptions such as "1. It is made up of elements in fixed proportions" and "6. The substance melts or boils at a specific temperature" refer to a pure substance. Meanwhile, "2. The components can be readily separated, e.g. by filtration or distillation" and "5. The elements or compounds are not in fixed proportions" are indicative of a mixture.