States of Matter

• “States of Matter” is a fundamental topic in Chemistry that discusses the three basic states of matter: solid, liquid, and gas. Each state is distinguished by its unique characteristics.
• In solids, particles are tightly packed in a regular pattern. They vibrate about fixed positions, but the forces of attraction between them are strong enough to hold them in place.
• As a result, solids have a definite shape and volume. They cannot be compressed or squashed because there is no free space between particles.
• Solids can transition to liquids in a process known as melting. The temperature at which this happens is called the melting point.
• Liquids have a definite volume but not a definite shape. They take the shape of their container because particles can move past each other, but are too close together to be compressed.
• Liquid particles are still quite close, but have more energy than solid particles which allows them to move around more freely. Liquids can flow and their particles are in constant motion.
• Evaporation is the process by which a liquid changes into a gaseous state. The temperature at which this happens is the boiling point.
• Gases have neither a fixed shape nor volume. They take the shape and volume of their container because gas particles have high energy, are well separated and move randomly in all directions.
• Gas particles move quickly and are spread apart which makes gases easy to compress.
• Changes between these states of matter are called phase transitions, where energy is transferred.
• Heating makes particles move faster (increasing their kinetic energy), while cooling has the opposite effect.
• Matters can change from one state to another through processes such as melting, freezing, vaporisation, condensation, sublimation and deposition, both requiring and releasing energy.
• Ideal gas theory assumes a theoretical gas composed of many randomly moving point particles that do not interact except when they collide elastically.
• Elements and compounds can exist in any of the three states, depending on the temperature and pressure.
• Understanding the behaviour of matter in its different states forms the basis for many other topics in chemistry, such as gas laws, thermodynamics, and solution chemistry.