Solids, Liquids, and Gases

Section: Basic Concepts of States of Matter

Matter exists in three states: solid, liquid, and gas. This is primarily dependent on temperature and pressure.
Solids have a fixed shape and volume because the particles are packed closely together. The forces of attraction are strong and keep particles in a relatively fixed position.
Liquids have a definite volume, but their shape can change to fill the container they’re in. Particles are less tightly packed than in solids, giving them the ability to flow.
Gases have neither a defined shape nor volume. They expand to fill the container they’re in, as their particles are spread out and move freely due to weak forces of attraction.

Section: Transition Between States of Matter

Change between states of matter due to heating or cooling is termed as phase changes. These include melting, freezing, evaporation, condensation, sublimation, and deposition.
Melting is the transition from solid to liquid when heat is added. This is because the particles gain energy, causing them to vibrate more and break the bonds holding them in a rigid structure.
Freezing is the process of transition from a liquid to a solid when heat is removed. Here, particles lose energy and form a more stable, structured arrangement.
Evaporation is when a liquid transitions to a gas state. In this process, the most energetic particles escape from the liquid’s surface.
Condensation is the reverse process of evaporation where gas turns back into a liquid. This involves the loss of energy by the gas particles.
Sublimation is the direct transition from solid to gas, bypassing the liquid phase. Deposition is the reverse process, transitioning directly from gas to solid.

Section: Properties Based on Intermolecular Forces

Intermolecular forces are internal forces that hold molecules together. These forces could be London dispersion forces, dipole-dipole interactions, or hydrogen bonds.
The strength of these intermolecular forces determines the physical properties of substances such as boiling points, melting points, viscosity, and surface tension.
With a stronger intermolecular force, substances are more likely to exist in solid or liquid state at room temperature, have higher boiling points, and exhibit greater viscosity and surface tension.
Conversely, substances with weaker intermolecular forces are more likely to be gases at room temperature and have lower boiling points and less pronounced viscosity and surface tension.

Remember, a strong understanding of these concepts and properties allows better prediction and explanation of the behaviour of substances in different phases and under varying conditions.