1. Physical changes alter a substance's appearance or state without changing its chemical composition, like melting or boiling. Chemical changes, however, involve the rearrangement of atoms, forming new substances with different chemical compositions, such as rusting or combustion.

    Physical changes alter a substance’s appearance or state without changing its chemical composition, like melting or boiling. Chemical changes, however, involve the rearrangement of atoms, forming new substances with different chemical compositions, such as rusting or combustion.

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  2. Elements are classified based on their properties as metals, non-metals, or metalloids. Metals are typically shiny, malleable, and good conductors. Non-metals are dull, brittle, and poor conductors. Metalloids exhibit properties of both.

    Elements are classified based on their properties as metals, non-metals, or metalloids. Metals are typically shiny, malleable, and good conductors. Non-metals are dull, brittle, and poor conductors. Metalloids exhibit properties of both.

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  3. Antoine Laurent Lavoisier contributed to the definition of an element by proposing that it is a substance that cannot be broken down into simpler substances by chemical means. This definition laid the groundwork for modern chemistry's understanding of elemental composition.

    Antoine Laurent Lavoisier contributed to the definition of an element by proposing that it is a substance that cannot be broken down into simpler substances by chemical means. This definition laid the groundwork for modern chemistry’s understanding of elemental composition.

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  4. The term "element" was first used by the ancient Greek philosopher Empedocles around 450 BCE to describe substances that cannot be broken down further by ordinary chemical processes.

    The term “element” was first used by the ancient Greek philosopher Empedocles around 450 BCE to describe substances that cannot be broken down further by ordinary chemical processes.

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  5. Water undergoing a physical change from liquid to solid when freezing or from liquid to gas when boiling are examples of substances experiencing changes in state without altering their chemical composition.

    Water undergoing a physical change from liquid to solid when freezing or from liquid to gas when boiling are examples of substances experiencing changes in state without altering their chemical composition.

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