Pure Substances and Mixtures

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Pure Substance Noun

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[pyoor sub-stuhns]

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Pure Substance

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Matter with a definite, uniform composition that cannot be separated into smaller substances by any physical means.

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Example: Gold is a pure substance because it is an element, meaning it is made up of only one type of atom (gold atoms).

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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, which cannot be broken down into simpler substances.

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Example: This diagram shows a single atom of the element Sodium (Na), 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 from two or more different types of atoms that are chemically combined in a fixed ratio.

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Example: This diagram shows a molecule of carbon dioxide (CO₂), where one carbon atom is chemically bonded to two oxygen atoms, forming a compound.

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Mixture Noun

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[miks-cher]

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Mixture

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A combination of two or more substances that are not chemically bonded, where each substance retains its own properties.

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

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Homogeneous Mixture Noun

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

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Homogeneous Mixture

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A mixture that has a completely uniform composition and appearance throughout, with its components being evenly distributed.

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Example: This diagram shows a solution, a type of homogeneous mixture, where solute particles are uniformly distributed among solvent particles, making the mixture appear the same throughout.

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Solution Noun

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[suh-loo-shuhn]

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Solution

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A common term for a homogeneous mixture where one substance is dissolved evenly into another at a molecular level.

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Example: This diagram shows a solution, where a substance called the solute (the small particles) is evenly mixed into another substance called the solvent (the liquid).

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Colloid Noun

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[kol-oid]

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Colloid

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A mixture where microscopic particles are evenly dispersed but are not heavy enough to settle out over time.

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Example: A light beam passes through a solution invisibly but is scattered and visible in the colloid, demonstrating the Tyndall effect, a key property of colloids.

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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 that has a non-uniform composition, with its components not evenly distributed and often visibly distinguishable.

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Example: This diagram shows that when oil and water are mixed, they form a heterogeneous mixture where the oil droplets are visible and eventually separate.

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Mechanical Mixture Noun

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[muh-kan-i-kuhl miks-cher]

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Mechanical Mixture

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A type of heterogeneous mixture where the different components are large enough to be seen and separated by hand.

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Example: This bowl of trail mix is a mechanical mixture because you can clearly see the different parts—like nuts, raisins, and candies—physically mixed together.

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Suspension Noun

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[suh-spen-shuhn]

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Suspension

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A heterogeneous mixture containing solid particles large enough for sedimentation, which will settle out unless constantly agitated.

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Example: This diagram shows muddy water, a suspension, being separated by filtration. The solid mud particles are trapped by the filter, while the liquid water passes through.