Question 20

A penny made only of copper would be classified as a pure substance that is an element.

A penny composed entirely of copper is best classified as a pure substance that is an element because it consists solely of one type of atom, which is copper. This indicates that it has a uniform and definite composition.

A) pure substance that is a compound

This option is incorrect because a compound is formed when two or more different elements chemically combine in fixed proportions. Since a penny made only of copper contains only copper atoms, it cannot be classified as a compound.

B) heterogeneous mixture of two compounds

This option is incorrect as it describes a mixture in which the components remain distinct and can be physically separated. A penny made solely of copper does not consist of multiple components or compounds, but rather it is a single, uniform substance.

C) pure substance that is an element

This option is correct because a penny made only of copper contains only copper atoms, making it a pure substance. Elements are defined as substances that cannot be broken down into simpler substances by chemical means, and copper fits this definition.

D) homogeneous mixture of two elements

This option is incorrect because a homogeneous mixture consists of two or more different substances that are uniformly distributed. A penny made entirely of copper does not contain any other elements or compounds, thus it cannot be classified as a mixture.

Conclusion

The classification of a penny made only of copper as a pure substance that is an element is definitive because it consists entirely of copper atoms without any mixture of other elements or compounds. All other options fail to accurately describe the composition of the penny, as they suggest the presence of multiple components or different substances, which is not the case here.