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 substance retains its own properties. Mixtures can be homogeneous or heterogeneous.

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What is the difference between an element and a compound?

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An element is a pure substance that cannot be broken down into simpler substances, while a compound is a substance formed when two or more elements chemically combine in fixed proportions.

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What is a solution?

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A solution is a homogeneous mixture where one substance (the solute) is dissolved in another (the solvent). An example is saltwater.

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What happens to the properties of substances in a mixture?

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In a mixture, the individual substances retain their original properties.

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What is a chemical change?

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A chemical change occurs when substances combine or break apart to form new substances with different properties.

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What is a physical change?

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A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition.

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What is a heterogeneous mixture?

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A heterogeneous mixture is a mixture in which the components are not uniformly distributed, and different parts can be seen. An example is a salad.

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What is a homogeneous mixture?

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A homogeneous mixture is a mixture in which the composition is uniform throughout. An example is air.

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What is the law of definite proportions?

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The law of definite proportions states that a chemical compound always contains its component elements in fixed ratio by mass.