Elements, Compounds, and Mixtures

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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 gold (Au).

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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. Examples include water (H2O) and 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. The components can be separated by physical means. Examples include salad and air.

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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. Examples include saltwater and vinegar.

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What is a heterogeneous mixture?

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A heterogeneous mixture is a mixture that does not have a uniform composition and the different components can be seen. Examples include a salad and a bowl of cereal.

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What is the difference between a pure substance and a mixture?

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A pure substance has a constant composition and distinct properties, while a mixture contains two or more substances that retain their individual properties.

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What is a solution?

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A solution is a type of homogeneous mixture where one substance (the solute) is dissolved in another (the solvent). Examples include sugar in water.

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What is the law of definite proportions?

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The law of definite proportions states that a chemical compound always contains the same proportion of elements by mass.

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What is the law of multiple proportions?

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The law of multiple proportions states that when two elements form more than one compound, the ratios of the masses of the second element that combine with a fixed mass of the first element can be expressed as small whole numbers.

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What is a chemical formula?

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A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound or molecule. For example, H2O represents water.