7th Grade Chemistry Review

Front

What is a physical change?

Back

A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition. Examples include melting, freezing, and boiling.

Front

What is a chemical change?

Back

A chemical change is a change that results in the formation of new chemical substances. Examples include burning, rusting, and digestion.

Front

How many valence electrons does an element with atomic number 15 have?

Back

5 valence electrons.

Front

What is the total number of atoms in the chemical formula 2CaCO₃?

Back

10 atoms.

Front

What happens to water when it boils?

Back

When water boils, it undergoes a physical change from a liquid to a gas.

Front

What is the definition of an atom?

Back

An atom is the smallest unit of matter that retains the properties of an element.

Front

What is a molecule?

Back

A molecule is a group of two or more atoms bonded together.

Front

What is the difference between an element and a compound?

Back

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

Front

What is the periodic table?

Back

The periodic table is a tabular arrangement of chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties.

Front

What is the law of conservation of mass?

Back

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction.