Science Midterm Exam (7th Grade, NEW)

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What is a Chemical Change?

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A process where substances combine or break apart to form new substances, often accompanied by energy changes, color changes, or gas production.

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What is a Physical Change?

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A change that affects one or more physical properties of a substance without altering its chemical composition, such as melting or freezing.

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What is an Atom?

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The basic unit of a chemical element, consisting of a nucleus surrounded by electrons.

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What is a Molecule?

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A group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound.

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What is a Compound?

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A substance formed when two or more different elements are chemically bonded together.

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What is a Mixture?

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A combination of two or more substances that are not chemically bonded and can be separated by physical means.

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How do you determine the total number of atoms in a chemical formula?

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Add the subscripts of all the elements in the formula. For example, in C3H7NO2, there are 3 (C) + 7 (H) + 1 (N) + 2 (O) = 13 total atoms.

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What is Neon?

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A colorless, odorless, inert gas that is a member of the noble gases group in the periodic table.

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What is the difference between an element and a compound?

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An element is a pure substance made of only one type of atom, while a compound is made of two or more different types of atoms chemically bonded together.

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What is the significance of the periodic table?

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The periodic table organizes all known elements based on their atomic number, electron configuration, and recurring chemical properties.