Physical and Chemical Changes

Front

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 melting, freezing, and dissolving.

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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. It involves a chemical reaction and includes processes like burning, cooking, and rusting.

Front

What are some signs that a chemical reaction has occurred?

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Signs of a chemical reaction include the formation of a gas, a change in color, the formation of a precipitate, and a change in temperature.

Front

What happens to water during evaporation?

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During evaporation, water changes from a liquid to a gas, usually due to an increase in temperature or decrease in pressure.

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What happens to water during condensation?

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During condensation, water vapor (gas) cools and changes back into liquid water, often forming droplets.

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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 alter the chemical composition of a substance, while a chemical change results in the formation of new substances.

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Can a chemical change be reversed?

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Some chemical changes can be reversed through other chemical reactions, but many are irreversible under normal conditions.

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What is an example of a chemical change involving food?

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Cooking an egg is an example of a chemical change, as it transforms the raw egg into a new substance with different properties.

Front

What is the role of energy in chemical changes?

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Energy is often required to break bonds in reactants and form new bonds in products during a chemical change.

Front

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.