Pre-Assessment - Elements and Compounds

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What is a chemical change?

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A chemical change is a process where substances combine or break apart to form new substances, often accompanied by energy changes, color changes, gas production, or precipitate formation.

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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. Examples include elements and compounds.

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How is a mixture different from a compound?

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A mixture is a combination of two or more substances that retain their individual properties and can be separated by physical means, while a compound is a substance formed when two or more elements chemically bond together.

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What evidence indicates a chemical change has occurred?

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Evidence of a chemical change includes gas production, color change, temperature change, formation of a precipitate, or a change in odor.

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What is the definition of an element?

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An element is a pure substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom.

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What is a compound?

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A compound is a substance formed when two or more elements chemically bond together in a fixed ratio, resulting in properties different from the individual elements.

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What happens during a physical change?

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During a physical change, the form of a substance changes, but its chemical composition remains the same. Examples include melting, freezing, and dissolving.

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What is the difference between evaporation and condensation?

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Evaporation is the process where liquid turns into vapor, while condensation is the process where vapor turns back into liquid.

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What is the role of hydrochloric acid in chemical reactions?

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Hydrochloric acid is a strong acid that can react with metals and carbonates, often producing hydrogen gas or carbon dioxide as a byproduct.

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What is the formula for magnesium chloride?

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The chemical formula for magnesium chloride is MgCl2.