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 that are not chemically bonded. 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 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 hydrogen, oxygen, and gold.

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What is a compound?

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A compound is a substance formed when two or more elements are chemically bonded together. Examples include water (H2O) and carbon dioxide (CO2).

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What is an atom?

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An atom is the smallest unit of matter that retains the properties of an element. It consists of protons, neutrons, and electrons.

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What is a molecule?

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A molecule is a group of two or more atoms bonded together. Molecules can be made of the same or different elements.

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What is a heterogeneous mixture?

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A heterogeneous mixture is one that does not have a uniform composition and the individual components can be seen (e.g., a mixture of sand and salt).

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What is a homogeneous mixture?

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A homogeneous mixture is one that has a uniform composition throughout, and the individual components are not distinguishable (e.g., air).

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What is the smallest unit of an element?

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The smallest unit of an element is an atom.