Physical and Chemical Changes

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Physical Change Noun

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[fiz-i-kuhl cheynj]

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Physical Change

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A change that alters the form or appearance of a substance but does not change its chemical composition.

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Example: Adding or removing energy causes water to change state between solid (ice), liquid, and gas (vapor), but the H2O molecules themselves remain unchanged.

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Chemical Change Noun

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[kem-i-kuhl cheynj]

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Chemical Change

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A transformation that results in the creation of new substances with different properties, also known as a chemical reaction.

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Example: Reactant molecules (methane and oxygen) break their bonds and their atoms rearrange to form new product molecules (carbon dioxide and water).

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Physical Property Noun

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[fiz-i-kuhl prop-er-tee]

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Physical Property

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A property that can be observed and measured without changing the chemical composition or identity of the substance.

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Example: This image shows that physical properties, such as color, size, volume, and density, are characteristics of a substance that can be observed or measured.

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Chemical Property Noun

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[kem-i-kuhl prop-er-tee]

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Chemical Property

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A characteristic that describes how a substance reacts with other substances or behaves under certain chemical conditions.

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Example: The image shows iron's chemical property of reactivity. When acid is added, a chemical change occurs, creating gas bubbles as a new substance.

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Intensive Property Noun

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[in-ten-siv prop-er-tee]

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Intensive Property

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A physical property that does not depend on the amount of matter present in a sample.

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Example: This image shows that no matter the amount of sulfur (large crystals vs. small powder), intensive properties like color (yellow) and melting point (115.2°C) stay the same.

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Extensive Property Noun

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[ek-sten-siv prop-er-tee]

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Extensive Property

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A physical property that depends on the amount of matter that a particular sample contains.

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Example: This diagram shows that when a container of air is physically divided, its volume is also divided, demonstrating that volume is an extensive property because it depends on the amount of substance.

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Malleability Noun

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[mal-ee-uh-bil-i-tee]

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Malleability

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A physical property of a material that allows it to be hammered or pressed into different shapes without breaking.

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Example: This image shows that malleability is a physical property where a metal, like gold, can be hammered into a thin sheet without breaking.

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Ductility Noun

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[duhk-til-i-tee]

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Ductility

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A physical property of a material that allows it to be stretched into a thin wire without breaking.

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Example: Ductility is a physical property of materials, like copper, that allows them to be stretched or pulled into a thin wire without breaking.

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Conductivity Noun

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[kon-duhk-tiv-i-tee]

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Conductivity

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A physical property describing a material's ability to allow heat or electricity to pass through it.

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Example: In a conductor without voltage, electrons move randomly. When voltage is applied, these free electrons flow in one direction, creating an electric current.

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Density Noun

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[den-si-tee]

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Density

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An intensive physical property representing the amount of mass per unit volume of a given substance.

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Example: This image shows that in the same amount of space, solids have particles packed tightly (high density), while gases have particles spread out (low density).