What state of matter has particles that are closely packed together but can slide past each other?

The correct answer is liquid. In the liquid state of matter, the particles are indeed closely packed together, allowing for a definite volume. However, unlike solids where the particles are tightly fixed in place, the particles in a liquid can move past one another. This ability to slide allows liquids to flow and take the shape of their container while maintaining a consistent volume.

In contrast, gases consist of particles that are spaced far apart and move freely, resulting in no definite shape or volume. Solids have particles that are rigidly structured and vibrate in fixed positions, providing them with a definite shape and volume. Plasma, which is another state of matter, consists of ionized particles that are not held together in a structured manner, behaving more like a gas due to the high energy levels present. Understanding these distinctions helps clarify why liquids are characterized by closely packed but mobile particles.