Physical Changes and Chemical Reactions

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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. Examples include freezing, melting, and dissolving.

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What is a chemical change?

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A chemical change is a process that involves the transformation of one or more substances into different substances with distinct properties. Evidence includes color change, gas production, and formation of a precipitate.

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What evidence indicates a chemical change has occurred?

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Evidence of a chemical change includes the production of a new substance, unexpected color change, temperature change, gas formation, or the formation of a precipitate.

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What happens during a combustion reaction?

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During a combustion reaction, a substance reacts with oxygen, producing heat and light, and typically results in the formation of carbon dioxide and water.

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What is rusting?

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Rusting is a chemical change that occurs when iron reacts with oxygen and moisture in the environment, forming iron oxide (rust).

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What is a precipitate?

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A precipitate is a solid that forms and settles out of a liquid mixture during a chemical reaction.

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What is the difference between a physical change and a chemical change?

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A physical change alters the form or appearance of a substance without changing its chemical composition, while a chemical change results in the formation of new substances.

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What is an example of a physical change?

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Freezing water is an example of a physical change, as it changes from liquid to solid without altering its chemical structure.

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What is an example of a chemical change?

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Burning wood is an example of a chemical change, as it produces ash, smoke, and gases, which are new substances.

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What is the role of temperature in chemical reactions?

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Temperature can affect the rate of chemical reactions; higher temperatures generally increase reaction rates by providing more energy to the reacting particles.