Properties & Changes, Factors affecting chemical reactions

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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 melting, freezing, and dissolving.

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NGSS.MS-PS1-4

NGSS.MS-PS3-4

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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. Examples include burning, rusting, and exploding.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

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What is density?

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Density is the mass of a substance divided by its volume, often expressed in grams per cubic centimeter (g/cm³). It helps determine whether an object will float or sink in a fluid.

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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.

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NGSS.MS-PS1-2

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

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A physical property can be observed without changing the substance's chemical identity (e.g., color, density), while a chemical property can only be observed during a chemical reaction (e.g., flammability, reactivity).

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What happens to the density of a substance when it is heated?

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Generally, when a substance is heated, its density decreases because the substance expands, increasing its volume.

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NGSS.MS-PS1-4

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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.

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NGSS.MS-PS1-4

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What is an example of a chemical change?

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An example of a chemical change is the rusting of iron.

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NGSS.MS-PS1-2

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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; it remains constant.

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NGSS.MS-PS1-5

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What factors can affect the rate of a chemical reaction?

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Factors that can affect the rate of a chemical reaction include temperature, concentration of reactants, surface area, and the presence of catalysts.

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NGSS.HS-PS1-5