States of Matter and Intermolecular Forces
This page introduces the fundamental concepts of states of matter and the role of intermolecular forces in determining physical properties.
Definition: Intermolecular forces (IMFs) are the attractions between molecules that determine a substance's state of matter at a given temperature.
The main types of intermolecular forces discussed are:
- Hydrogen bonding
- Dipole-dipole attraction
- Dispersion forces
These forces play a crucial role in determining various properties of substances, including:
- Vapor pressure
- Boiling point
- Physical state
Vocabulary: Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid in a closed container.
The guide emphasizes that energy is required to break intermolecular forces during phase changes. It also mentions different pressure units such as atmospheres (atm), kilopascals (kPa), and millimeters of mercury (mm Hg or torr).
Highlight: Changes in pressure, temperature, or volume can cause a change in a substance's physical state.
The page then provides a detailed overview of the three states of matter:
- Solids: Closely packed molecules, definite volume, incompressible, lowest energy
- Liquids: Molecules relatively close, definite volume, takes shape of container, middle energy
- Gases: Molecules far apart, no definite volume, takes shape of container, compressible, highest energy
Example: Phase changes include melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), and deposition (gas to solid).
The guide also touches on the concepts of temperature, pressure, and energy in relation to states of matter. It introduces the first law of thermodynamics and discusses kinetic and potential energy in the context of phase changes.
