The Mole Concept

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Mass Noun

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[mas]

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Mass

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A fundamental measure of the amount of matter that an object contains, which is one of the primary ways to quantify matter.

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Example: This image shows a balance scale comparing a 1-gram weight to an apple, demonstrating that the apple has more mass because it causes the scale to tip down.

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Volume Noun

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[vol-yoom]

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Volume

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The amount of three-dimensional space that a substance or object occupies, used as a primary way to quantify matter.

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Example: This image shows how to measure the volume of a liquid by correctly reading the measurement scale on a graduated cylinder at the meniscus.

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Conversion Factor Noun

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[kuhn-vur-zhuhn fak-ter]

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Conversion Factor

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A ratio derived from the equality between two different units that can be used to convert from one unit to another.

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Example: This balance shows that one large sphere is equal to four small spheres, just like a conversion factor shows how two different units are equal.

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Mole (mol) Noun

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[mohl]

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Mole (mol)

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The SI base unit for amount of substance, defined as containing 6.02 x 10²³ representative particles of that substance.

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Example: This diagram shows that one mole is a specific amount of a substance, defined as 12 grams of carbon-12, which contains 602 sextillion atoms (Avogadro's number).

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Avogadro's Number Noun

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[ah-vuh-gah-drohz nuhm-ber]

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Avogadro's Number

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The number of representative particles contained in one mole of a substance, which is equal to 6.02 x 10²³.

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Example: This image shows that a specific, very large number of carbon atoms (Avogadro's number, 6.02 x 10²³) has a mass of exactly 12 grams.

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Representative Particle Noun

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[rep-ri-zen-tuh-tiv pahr-ti-kuhl]

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Representative Particle

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The specific type of particle present in a substance, which can be an atom, a molecule, or a formula unit.

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Example: For a compound like water, the representative particle is a single molecule. A mole of water contains 6.02 x 10²³ of these molecules.

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Atom Noun

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[at-uhm]

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Atom

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The smallest particle of a chemical element that retains its chemical properties and serves as the representative particle for elements.

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Example: This diagram shows an atom's structure, with a central nucleus of protons and neutrons, and electrons orbiting the nucleus.

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Molecule Noun

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[mol-i-kyool]

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Molecule

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An electrically neutral group of two or more atoms held together by chemical bonds, representing molecular compounds.

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Example: This image shows a single water molecule, which is formed when two hydrogen (H) atoms bond with one oxygen (O) atom.

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Formula Unit Noun

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[for-myoo-luh yoo-nit]

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Formula Unit

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The lowest whole-number ratio of ions in an ionic compound, which serves as the representative particle for ionic compounds.

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Example: This image shows one sodium ion (Na+) and one chloride ion (Cl-), representing the simplest whole-number ratio (1:1) in the ionic compound sodium chloride.

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Molar Mass Noun

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[moh-ler mas]

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Molar Mass

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The mass of one mole of a given chemical element or chemical compound, typically expressed in grams per mole (g/mol).

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Example: The molar mass of a compound (like CO2) is calculated by adding the atomic masses of each atom in the molecule (one Carbon and two Oxygens).