03 Classifying Matter

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What is an element?

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An element is a pure substance that cannot be broken down into simpler substances by chemical means. Examples include hydrogen (H), oxygen (O), and carbon (C).

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What is a compound?

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A compound is a substance formed when two or more elements are chemically bonded together. It can be represented by a chemical formula, such as water (H2O) or carbon dioxide (CO2).

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What is a mixture?

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A mixture is a combination of two or more substances that are not chemically bonded. Mixtures can be homogeneous (uniform composition) or heterogeneous (distinct, separate components).

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What is a homogeneous mixture?

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A homogeneous mixture is a mixture that has a uniform composition throughout. An example is saltwater, where the salt is evenly distributed in the water.

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What is a heterogeneous mixture?

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A heterogeneous mixture is a mixture where the components are not uniformly distributed, and different parts can be seen. An example is a salad.

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What is a physical property?

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A physical property is a characteristic of a substance that can be observed or measured without changing its chemical identity. Examples include color, melting point, and density.

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What is a chemical property?

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A chemical property is a characteristic of a substance that describes its ability to undergo a specific chemical change. Examples include flammability and reactivity with acids.

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

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A physical change alters the form or appearance of a substance without changing its chemical composition (e.g., melting ice). A chemical change results in the formation of new substances (e.g., rusting iron).

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What is a pure substance?

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A pure substance is a material that has a constant composition and consistent properties throughout. It can be an element or a compound.

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What is a suspension?

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A suspension is a heterogeneous mixture in which solid particles are dispersed in a liquid or gas but are not dissolved. The particles can settle over time, such as muddy water.