Accounting for Atoms

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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 and the fundamental building block of all matter in the universe.

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Example: This diagram shows an atom's structure: a central nucleus with protons and neutrons, surrounded by electrons moving in distinct shells or energy levels.

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Substance Noun

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[suhb-stuhns]

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Substance

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A particular kind of matter with uniform properties, which can be a pure element or a specific chemical compound.

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Example: Gold is a pure substance because it is made of only one type of atom, making its composition uniform throughout.

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Molecule Noun

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[mol-i-kyool]

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Molecule

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A group of two or more atoms chemically bonded together, representing the smallest fundamental unit of a chemical compound.

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Example: This image shows a molecule, which is made of smaller particles called atoms (the spheres) that are joined together by chemical bonds.

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Property Noun

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[prop-er-tee]

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Property

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A characteristic of a substance that can be observed or measured, which is used to identify it.

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Example: This image shows chalk sticks of different colors. Color is an observable property, which is a characteristic used to describe and identify matter.

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Chemical Reaction Noun

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[kem-i-kuhl ree-ak-shuhn]

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Chemical Reaction

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A process that involves the rearrangement of the atomic structure of a substance, resulting in the formation of new substances.

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Example: Reactants (like methane and oxygen) on the left rearrange their atoms to form new substances, the products (like carbon dioxide and water), on the right.

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Reactant Noun

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[ree-ak-tuhnt]

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Reactant

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A substance that takes part in and undergoes change during a chemical reaction; it is a starting material.

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Example: This image shows a chemical reaction where the starting substances on the left, Methane and Oxygen, are the reactants that will be changed.

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Product Noun

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[prod-uhkt]

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Product

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A new substance that is formed as the result of a chemical reaction when reactants are chemically transformed.

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Example: In a chemical reaction, the new substances that are formed, like the two water molecules (2H₂O) on the right, are called the products.

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Conservation of Atoms Noun

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[kon-ser-vey-shuhn uhv at-uhmz]

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Conservation of Atoms

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The scientific principle stating that atoms are not created or destroyed during a chemical reaction, only rearranged into new molecules.

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Example: This diagram shows that in a chemical reaction, atoms are rearranged to form new molecules, but no atoms are created or destroyed.

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Mass Noun

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[mas]

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Mass

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The measure of the amount of matter in an object or substance, which is conserved during a chemical reaction.

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Example: This image defines mass (m) as a scalar quantity measured in kilograms (kg) within the context of Newton's second law formula, F=ma.

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Model Noun

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[mod-l]

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Model

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A representation used to explain and predict the behavior of real objects or systems, especially those too small to see.

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Example: This diagram is a scientific model that simplifies the Moon's orbit, showing how Earth's gravity pulls on the Moon to keep it in a circular path.