The option that correctly compares a pure substance to a mixture is: B. A pure substance can only be separated by chemical means, whereas some mixtures can be separated by physical means.
A pure substance can be defined as a substance that has a definite and constant (fixed) structure and they are typically made up of only a kind of particles. Thus, a pure substance is a chemical substance that has a constant (fixed) chemical composition and properties.
As a result of a pure substance being a chemical substance, it cannot be separated into its constituents by a physical separation technique or method.
Instead, a pure substance being a chemical substance can only be separated by chemical separation technique or method.
In contrast, mixtures can be separated by a physical separation technique or method.
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