Physical and Chemical Changes; Law of Conservation of Mass

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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 changes in state (like melting or boiling) 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. It involves the breaking and forming of bonds between atoms. Examples include rusting of iron and burning of wood.

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What is the Law of Conservation of Mass?

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The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. The total mass of the reactants equals the total mass of the products.

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What are reactants in a chemical reaction?

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Reactants are the starting substances in a chemical reaction that undergo change to form products.

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What are products in a chemical reaction?

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Products are the substances that are formed as a result of a chemical reaction.

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What is an indicator of a chemical change?

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Indicators of a chemical change include color change, gas production (bubbles), temperature change, and the formation of a precipitate.

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What is a balanced chemical equation?

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A balanced chemical equation has the same number of each type of atom on both sides of the equation, indicating that mass is conserved.

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What happens to the mass of reactants when gases are released during a reaction?

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When gases are released during a reaction, the total mass of the products may be less than the total mass of the reactants because the gas escapes into the atmosphere.

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Why is boiling water considered a physical change?

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Boiling water is considered a physical change because it changes from liquid to gas (water vapor) without changing its chemical composition; it remains H2O.

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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.