Which of the following is NOT a category of matter?

Matter is defined as anything that has mass and takes up space. It is primarily classified into categories such as atoms, elements, and compounds, which represent different forms of matter.

Atoms are the basic building blocks of matter, consisting of protons, neutrons, and electrons. They combine to form elements, which are pure substances made up of only one type of atom. Compounds, on the other hand, are substances formed when two or more different types of atoms chemically bond together, resulting in a new substance with its own unique properties.

Energy, however, is not considered a category of matter. Instead, it refers to the ability to do work or produce change and exists in various forms, such as kinetic, potential, thermal, and chemical energy. While energy can interact with matter and cause changes in its state or motion, it does not have mass or occupy space, which are essential characteristics that define matter. Thus, identifying energy as something separate from matter makes it clear why it is not a category of matter.