Which of the following best describes chalk in terms of the classification of matter?
A
A homogeneous mixture
B
A pure substance (compound)
C
A pure substance (element)
D
A heterogeneous mixture
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Understand the classification of matter: Matter can be classified as pure substances or mixtures. Pure substances include elements and compounds, while mixtures can be homogeneous or heterogeneous.
Recall that a pure substance (element) consists of only one type of atom, such as oxygen (O\_2) or gold (Au).
Recognize that a pure substance (compound) consists of two or more elements chemically combined in a fixed ratio, such as water (H\_2O) or carbon dioxide (CO\_2).
Identify that a homogeneous mixture has a uniform composition throughout, like salt dissolved in water, where you cannot distinguish different parts.
Note that a heterogeneous mixture has visibly different components or phases, such as chalk, which contains particles of calcium carbonate mixed with other materials, making it non-uniform in composition.