Review Chemistry

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What is a molecule?

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A molecule is a group of two or more atoms bonded together. Molecules can be made of the same type of atoms (like O2) or different types (like H2O).

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What is a compound?

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A compound is a substance formed when two or more different elements are chemically bonded together, such as water (H2O) or carbon dioxide (CO2).

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What is the difference between an element and a compound?

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An element is a pure substance that cannot be broken down into simpler substances, while a compound is made up of two or more elements chemically combined.

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What is a pure substance?

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A pure substance is a material that has a constant composition and consistent properties throughout, such as elements and compounds.

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What is a physical change?

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A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition, such as melting ice.

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What is a chemical change?

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A chemical change occurs when a substance transforms into a different substance with different properties, such as burning wood.

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What is a coefficient in a chemical equation?

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A coefficient is a number placed in front of a chemical formula in an equation to indicate how many molecules or moles of that substance are involved.

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What is a subscript in a chemical formula?

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A subscript is a number written below and to the right of a chemical symbol that indicates the number of atoms of that element in a molecule.

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What evidence indicates a chemical change has occurred?

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Evidence of a chemical change includes color change, gas production, temperature change, and the formation of a precipitate.

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What is an example of a physical change?

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An example of a physical change is the melting of ice into water.