Unit 4 Lesson 7: Element, Compound, Molecule?

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What is a compound?

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A compound is a substance formed when two or more different elements are chemically bonded together. Example: Water (H2O) is a compound made of hydrogen and oxygen.

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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. It is made of only one type of atom. Example: Oxygen (O) is an element.

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What are molecules?

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Molecules are groups of two or more atoms bonded together. They can be made of the same or different elements. Example: O2 (oxygen gas) is a molecule made of two oxygen atoms.

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What are the basic building blocks of matter?

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Atoms are the basic building blocks of all matter. They are the smallest units of an element that retain the properties of that element.

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What is the difference between a mixture and a compound?

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A mixture is a combination of two or more substances that are not chemically bonded, while a compound is a substance formed from the chemical bonding of two or more different elements.

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Can elements be separated into simpler substances?

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No, elements cannot be separated into simpler substances by chemical means. They are pure substances made of only one type of atom.

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What is a chemical formula?

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A chemical formula is a way of expressing the composition of a compound using symbols for the elements and numbers to indicate the ratio of atoms. Example: CH3CHO for acetic acid.

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What does the subscript in a chemical formula indicate?

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The subscript in a chemical formula indicates the number of atoms of the element in the molecule. For example, in H2O, the '2' indicates there are two hydrogen atoms.

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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. Example: Saltwater is a homogeneous mixture.

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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 can be easily distinguished. Example: Salad is a heterogeneous mixture.