Elements, Compounds, and Mixtures

A chemist is studying an unknown substance. He can break it into its elemental components only by using chemical means.

Q. Based on this observation, how should the unknown substance be classified?

pure substance
A teacher makes the following statement.

“Gasoline boils at a relatively low temperature (about 150°C). The kerosene is removed at around 200°C, followed by diesel oil at 300°C and fuel oil at around 370°C.”

Q. What topic is the teacher most likely talking about?

filtration of a pure substance
Which cannot be separated into simpler substances?
The table describes how some substances were formed.

Q.Based on the given descriptions, which substance is most likely a mixture?

Which method would be best for separating the components of a mixture that is made from two different liquids?
The chemical formula for emerald is Be3Al2(SiO3)6. An emerald can be described as
a pure substance because it is a compound.
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A solid precipitate is formed from the reaction of lead nitrate and sodium chromate.

Q. What would be the best method to separate this solid from the solution?

The table shows the percentages of hydrocarbons that are found in a sample of crude oil.

Q.Based on the given information, what is the best classification for this sample of crude oil?

a mixture
What can a drop of liquid mercury be described as?
a pure substance and an element
A rock can be broken down into different kinds of substances by physical processes. No chemical reactions are needed to separate different parts of a rock into pure substances. This is because a rock is a(n)