Physical and Chemical Changes Review

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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 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. It involves a chemical reaction and can be identified by changes in color, temperature, gas production, or the 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 a change in color, temperature, the production of gas, or the formation of a solid (precipitate) from a solution.

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How does temperature affect the state of matter?

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Temperature affects the state of matter by influencing the movement of molecules. Adding heat increases molecular movement, causing solids to melt into liquids or liquids to evaporate into gases. Removing heat decreases molecular movement, causing gases to condense into liquids or liquids to freeze into solids.

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What happens to the molecules of water when heat is added?

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When heat is added to water, the molecules move faster and farther apart, which can lead to a change in state, such as from liquid to gas.

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What happens to the molecules of water when heat is removed?

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When heat is removed from water, the molecules move slower and closer together, which can lead to a change in state, such as from gas to liquid or liquid to solid.

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What is an example of a physical change?

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An example of a physical change is ice melting into water. The ice changes state from solid to liquid, but its chemical composition (H2O) remains the same.

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What is an example of a chemical change?

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An example of a chemical change is burning wood. The wood reacts with oxygen to form ash, smoke, and gases, resulting in new substances.

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What is the significance of a change in color during an experiment?

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A change in color during an experiment can indicate a chemical change has occurred, suggesting that new substances have formed.

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What is the role of heat in chemical reactions?

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Heat can provide the energy needed to initiate or accelerate chemical reactions, often resulting in changes in temperature and the formation of new substances.