Properties and changes of matter

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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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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 the breaking and forming of bonds. Examples include rusting, burning, and digestion.

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What is the difference between physical and chemical properties?

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Chemical properties are only observable when a substance is changing into a different substance, while physical properties can be observed or measured without changing the substance's identity.

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What is density?

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Density is a physical property defined as mass per unit volume of a substance, typically expressed in grams per milliliter (g/mL) or kilograms per cubic meter (kg/m³).

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What units are used to measure volume?

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Common units for measuring volume include milliliters (mL), liters (L), and cubic centimeters (cm³).

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Is dissolving sugar in water a physical or chemical change?

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Dissolving sugar in water is a physical change because the sugar can be recovered by evaporating the water.

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What are examples of physical properties?

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Examples of physical properties include color, odor, melting point, boiling point, density, and solubility.

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What are examples of chemical properties?

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Examples of chemical properties include reactivity with acids, flammability, and the ability to oxidize.

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Can physical changes be reversed?

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Many physical changes can be reversed, such as freezing and melting, but some may not be easily reversible, like breaking a glass.

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Can chemical changes be reversed?

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Chemical changes are often not reversible by simple physical means. For example, burning wood creates ash and gases that cannot be turned back into wood.