Pure Substances and Mixtures

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What is a pure substance?

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A pure substance is a material that has a constant composition and consistent properties throughout. Examples include elements and compounds.

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What is a mixture?

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A mixture is a combination of two or more substances where each retains its own properties. Mixtures can be homogeneous or heterogeneous.

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What is the difference between a homogeneous mixture and a heterogeneous mixture?

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A homogeneous mixture has a uniform composition throughout (e.g., saltwater), while a heterogeneous mixture has a non-uniform composition (e.g., salad).

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What is a compound?

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A compound is a substance formed when two or more elements chemically bond together in a fixed ratio (e.g., water, H2O).

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Can compounds be separated by physical means?

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No, compounds can only be separated by chemical means.

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What is an element?

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An element is a pure substance that cannot be broken down into simpler substances by chemical means. Examples include oxygen (O) and gold (Au).

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Is salt a compound or a mixture?

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Salt (sodium chloride, NaCl) is a compound.

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What is an example of a homogeneous mixture?

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An example of a homogeneous mixture is sugar dissolved in water.

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What is an example of a heterogeneous mixture?

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An example of a heterogeneous mixture is a salad or a mixture of sand and iron filings.

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What does it mean for a substance to be chemically pure?

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A chemically pure substance contains only one type of particle and has a consistent composition and properties.