Pure Substances and Mixtures
Two classifications of matter are pure substances and mixtures. Pure substances have a definite chemical composition, cannot be separated by physical means, and consist of one or more types of atoms.
Mixtures do not have a definite chemical composition, can be separated by physical means, and consist of two or more types of substances.
A student constructs models of elements, molecules, compounds, and mixtures using different colors of balls and black plastic sticks. A key for each element and the chemical bond is shown.
Multiple Choice Question
A model of a substance in a container is shown.
The model shows a clear jar with a lid containing three models of substances. One substance has a blue ball attached to two red balls. A second substance has one red ball attached to a light blue ball. And a third substance consists of a single green ball.
Which best describes the substance in the container?
A.
It is a mixture because it has a definite chemical composition and cannot be separated by physical means.
B.
It is a mixture because it does not have a definite chemical composition and can be separated by physical means.
C.
It is a pure substance because it has a definite chemical composition and cannot be separated by physical means.
D.
It is a pure substance because it does not have a definite chemical composition and can be separated by physical means.
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The best answer that describes the substance in the container is:
B. It is a mixture because it does not have a definite chemical composition and can be separated by physical means.
This is because the model contains multiple different substances (the blue and red balls, the red and light blue balls, and the single green ball), indicating that it is not a pure substance but rather a mixture of different components.
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