Question

matter consists of pure substances and mixtures. pure substances include elements and compounds, which are atoms from two or more elements chemically bonded. mixtures contain two or more substances that are combined but are not chemically bonded. if you dissolve salt in water, for example, you create a mixture: saltwater. the salt and water are still present, and their chemical compositions are the same after you mix them. if you add heat to that mixture, the water changes in state from a liquid to a gas. after letting all the water evaporate, youre left with the salt. that physical change separates your mixture back into its two parts: water and salt. neither creating nor separating a mixture results in a chemical change.
in the passage above, what is the purpose of the underlined sentence?
choose one option
a to describe how one mixture can be separated
b to show how seawater can be useful
c to explain how to make your own salt
d to illustrate an effect of evaporation

Explanation:

The underlined sentence describes the process of separating a mixture (saltwater) by letting the water evaporate and being left with salt. This directly relates to showing how a mixture can be separated. Option B is about seawater's usefulness which is not the focus. Option C is about making salt which is not the main point. Option D is too narrow as it's about the overall separation of the mixture (a broader concept than just the effect of evaporation).

Answer:

A. to describe how one mixture can be separated