Plasma is the fourth state of matter, consisting of highly ionized gas containing free electrons and positive ions. It is highly conductive and occurs at extremely high temperatures (e.g., in stars, lightning, and neon signs).

Core Study Guide

Matter and States of Matter

The fundamental substance of the physical universe.

Matter is anything that has mass and occupies space. It exists in distinct physical states governed by temperature and pressure.

According to the Kinetic Molecular Theory, all matter is made of particles in constant motion. The strength of intermolecular forces determines whether a substance behaves as a solid, liquid, or gas.

Key Takeaways

•Matter exists primarily as solid, liquid, or gas, plus high-energy plasma.
•Phase changes occur when thermal energy is added or removed, changing particle motion.
•Physical properties describe state without altering chemical identity; chemical properties govern reactivity.

Core Concepts & Definitions

1Kinetic Molecular Theory

Particles in solids vibrate in fixed grids; liquid particles slide past each other; gas particles move rapidly with negligible attraction.

•Solids have definite shape and volume.

•Liquids have definite volume but assume container shape.

•Gases expand to fill any container volume.

Quick Revision Notes

•Phase changes are physical changes because the molecular formula of the substance remains identical.
•Density = Mass / Volume. Density determines whether substances separate into distinct layers.