Physical and Chemical Changes

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What is a physical change?

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A physical change is a change that does not alter the chemical composition of a substance. Examples include changes in state (like melting or freezing) and changes in shape or size.

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What is a chemical change?

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A chemical change is a change that results in the formation of new chemical substances. Indicators include color change, gas production, heat production, and light emission.

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What happens during a phase change?

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During a phase change, a substance changes from one state of matter to another (solid, liquid, gas) without changing its chemical composition.

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What is an example of a physical change?

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Cutting wood is an example of a physical change because it alters the size and shape of the wood but does not change its chemical composition.

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What is an example of a chemical change?

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The formation of salt (NaCl) from sodium and chlorine is an example of a chemical change because it creates a new substance.

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What are some indicators of a chemical change?

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Indicators of a chemical change include a change in color, the production of gas, the release or absorption of heat, and the emission of light.

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Are physical changes reversible?

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Yes, physical changes are often reversible. For example, ice melting into water can be frozen back into ice.

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Are chemical changes reversible?

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Chemical changes are usually not reversible without another chemical reaction. For example, burning wood creates ash and gases that cannot be turned back into wood.

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

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A physical change does not create a new substance, while a chemical change results in the formation of new substances.

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What is an example of a reversible physical change?

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Melting ice is an example of a reversible physical change, as it can be frozen back into ice.