Molar Mass

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Mole Noun

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[mohl]

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Mole

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A standard scientific unit for measuring large quantities of small entities like atoms, where one mole equals 6.02x10^23 particles.

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Example: This diagram shows that one mole is a specific amount of a substance, defined by the number of atoms in exactly 12 grams of carbon-12.

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Avogadro's Number Noun

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

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Avogadro's Number

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The number of representative particles in one mole of a substance, precisely defined as 6.02 x 10^23 particles per mole.

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Example: This image defines Avogadro's number as the quantity in one mole (6.02 x 10^23) and shows how to use it to calculate the number of atoms.

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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, in grams, of one mole of a substance, which is expressed in the units of grams per mole (g/mol).

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Example: This image shows how to find the molar mass of water (H₂O) by adding the individual atomic masses of two hydrogen atoms and one oxygen atom.

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Molecular Weight Noun

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[muh-lek-yuh-ler weyt]

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Molecular Weight

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A term used synonymously with molar mass, representing the total mass in grams of all atoms in one mole of a molecule.

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Example: This image shows a water molecule is built from two hydrogen atoms and one oxygen atom. To find its molecular weight, you add the individual weights of these three atoms.

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Atomic Mass Noun

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[uh-tom-ik mas]

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Atomic Mass

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The mass of a single atom of a chemical element, typically expressed in atomic mass units or as grams per mole.

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Example: Atomic mass is calculated from the particles in the atom's nucleus; this image shows the protons (green) and neutrons (red) clustered in the center.

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Dimensional Analysis Noun

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[dih-men-shuh-nl uh-nal-uh-sis]

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Dimensional Analysis

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A problem-solving method that uses conversion factors between different units to systematically solve for a desired quantity in calculations.

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Example: This image shows how to use dimensional analysis to convert units by multiplying a starting amount by a conversion factor, ensuring unwanted units cancel out.

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Representative Particles Noun

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

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Representative Particles

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The smallest unit in which a substance naturally exists, such as atoms for elements or molecules for covalent compounds.

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Example: This image shows a single water molecule, which is an example of a representative particle for a molecular compound. Scientists count these particles using moles.

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Coefficient Noun

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[koh-uh-fish-uhnt]

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Coefficient

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A number placed in front of a chemical formula in an equation that indicates the number of moles or molecules involved.

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Example: The image shows that two molecules of oxygen (O₂) are needed and two molecules of water (H₂O) are made. The number '2' is the coefficient.

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Subscript Noun

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[suhb-skript]

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Subscript

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A number written to the lower right of a chemical symbol, indicating the number of atoms of that element in a molecule.

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Example: The image shows a subscript is a small number (like the '22' at the top) written below the normal line of text.

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Ion Noun

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[ahy-on]

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Ion

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An atom or group of atoms that has a net positive or negative charge from losing or gaining one or more electrons.

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Example: A neutral sodium atom (11 protons, 11 electrons) loses one electron to become a sodium ion (11 protons, 10 electrons), giving it a positive charge.