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 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. Examples include water (H2O) and sodium chloride (NaCl).

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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 individual substances retain their own properties. Examples include air and salad.

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How can you identify a compound?

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A compound can be identified by its chemical formula, which shows the elements present and their ratios. For example, H2O indicates two hydrogen atoms and one oxygen atom.

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What is the difference between a mixture of elements and a mixture of compounds?

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A mixture of elements contains two or more elements that are not chemically combined, while a mixture of compounds contains two or more compounds that are not chemically combined.

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Is water (H2O) an element or a compound?

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Water (H2O) is a compound because it is made up of two hydrogen atoms and one oxygen atom chemically bonded together.

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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 air.

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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 individual components can be seen. Examples include a salad or a mixture of sand and iron filings.

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What is the periodic table?

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The periodic table is a tabular arrangement of all known elements, organized by increasing atomic number and grouped by similar properties.

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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, regardless of the amount or source.