Pure Substances and Mixtures

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Matter Noun

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[mat-er]

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Matter

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Anything that has mass and takes up space, also known as volume, and is composed of atoms.

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Example: This image shows gold bars, which are an example of a pure substance. All matter, like these gold bars, has mass and takes up space.

Front

Pure Substance Noun

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[pyoor suhb-stuhns]

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Pure Substance

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A substance with a fixed chemical composition and distinct properties, consisting of only one type of particle.

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Example: This image shows that pure substances are made of either elements (like tin and diamond) or compounds (like sugar and water), both having a fixed composition.

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Mixture Noun

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[miks-cher]

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Mixture

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A physical combination of two or more substances that are not chemically bonded and retain their individual properties.

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Example: This diagram shows salt and water, two separate substances, being physically combined and stirred to form a saltwater solution, which is a type of mixture.

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Element Noun

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[el-uh-muhnt]

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Element

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A pure substance consisting of only one type of atom that cannot be broken down by chemical means.

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Example: This diagram shows a single atom of the element Sodium, illustrating that an element is a pure substance made of only one type of atom.

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Compound Noun

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[kom-pound]

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Compound

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A pure substance formed when two or more different elements are chemically bonded together in a fixed ratio.

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Example: This image shows a model of a carbon dioxide (CO2) molecule, where different atoms (one carbon, two oxygen) are chemically bonded together to form a compound.

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Atom Noun

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[at-uhm]

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Atom

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The basic unit of a chemical element, consisting of a central nucleus surrounded by one or more electrons.

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Example: This diagram shows an oxygen atom, with a central nucleus containing protons and neutrons, and electrons orbiting the nucleus in distinct energy shells.

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Molecule Noun

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[mol-i-kyool]

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Molecule

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A neutral group of two or more atoms held together by covalent chemical bonds, forming the smallest particle of a substance.

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Example: This image shows a single water molecule (H₂O), where two hydrogen (H) atoms are chemically bonded to one oxygen (O) atom.

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Chemical Bond Noun

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[kem-i-kuhl bond]

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Chemical Bond

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A lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds.

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Example: This image shows how two hydrogen (H) atoms and one oxygen (O) atom are held together by chemical bonds to form a single water molecule.

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Homogeneous Mixture Noun

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[hoh-moh-jee-nee-uhs miks-cher]

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Homogeneous Mixture

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A mixture with a uniform composition and appearance throughout, where individual components are not visually distinguishable.

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Example: This diagram shows a solution, a type of homogeneous mixture where solute particles are evenly distributed throughout the solvent, making the mixture look uniform.

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Heterogeneous Mixture Noun

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[het-er-uh-jee-nee-uhs miks-cher]

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Heterogeneous Mixture

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A mixture with a non-uniform composition in which the individual components can be seen and are not evenly distributed.

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Example: When oil and water are shaken together (agitation), they form a heterogeneous mixture where oil droplets are visible, but they eventually separate back into layers.