7th grade Midterm review Units 1-3 Part 1

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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. Example: Gasoline burns in a car engine.

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What are reactants in a chemical reaction?

Back

Reactants are the starting substances in a chemical reaction that undergo change to form products. Example: In the reaction methane + oxygen, methane and oxygen are the reactants.

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How do chemical reactions create new substances?

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Chemical reactions create new substances by breaking apart atoms and reassembling them in new combinations.

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What is a coefficient in a chemical equation?

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A coefficient is a number placed in front of a chemical formula in an equation to indicate how many molecules or moles of that substance are involved. Example: In 2H2 + O2 -> 2H2O, '2' is the coefficient.

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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. Example: Melting ice.

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

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

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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 air, forming iron oxide (rust).

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What is combustion?

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Combustion is a chemical reaction that occurs when a substance reacts rapidly with oxygen, producing heat and light. Example: Burning wood.

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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. Example: In the reaction of methane and oxygen, carbon dioxide and water are the products.

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What is a chemical equation?

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A chemical equation is a symbolic representation of a chemical reaction, showing the reactants and products along with their quantities.