Overview
This lecture covers the particulate nature of matter, including the kinetic theory, Brownian motion, diffusion, and gas pressure, focusing on the fundamental properties and behavior of solids, liquids, and gases.
Nature and Structure of Matter
- All matter is made up of tiny particles.
- Atoms are the smallest particles that cannot be broken down chemically or physically.
- Molecules are particles formed when atoms join together.
- Ions are atoms or molecules that carry a positive or negative charge.
- There are three states of matter: solids, liquids, and gases.
Properties of States of Matter
- Solids have a fixed shape and volume due to strong forces and lattice arrangement.
- Liquids have a fixed volume but take the shape of their container; particles are close but can move past each other.
- Gases have neither fixed shape nor volume; particles are far apart, move quickly, and spread out to fill a container.
Changes of State
- Melting: solid turns to liquid at the melting point by gaining heat.
- Freezing: liquid turns to solid at the freezing point by losing heat.
- Boiling: liquid turns to gas at the boiling point by gaining heat.
- Evaporation: some particles in a liquid turn to gas at any temperature.
- Condensation: gas turns to liquid by losing heat.
- Sublimation: some solids (like COâ‚‚, naphthalene, iodine) change directly to gas.
Heating and Cooling Curves
- Heating curve: temperature remains constant during changes of state; energy is used to change state, not temperature.
- Cooling curve: process is reversed; temperature is steady during condensation and freezing.
Kinetic Theory Explanation
- States of matter differ by particle arrangement, movement, and forces of attraction.
- Changing temperature alters particle energy, movement, and state.
- Melting and boiling occur as particles gain enough energy to break free.
- Freezing and condensation occur as particles lose energy and come closer together.
Brownian Motion
- Brownian motion is the random movement of particles suspended in liquids or gases due to collisions with smaller, moving particles.
- Evident in phenomena such as smell spreading, dust dancing in air, and spreading of colored substances in water.
Diffusion
- Diffusion is the mixing of particles as they collide and move randomly.
- Rate of diffusion is faster for lighter particles and at higher temperatures.
Gas Pressure
- Gas pressure results from particles colliding with container walls.
- Increasing temperature raises particle speed and pressure.
- Compressing gas increases collision frequency and pressure; solids and liquids cannot be compressed in this way.
Key Terms & Definitions
- Atom — Smallest unit of an element, cannot be broken down further.
- Molecule — Particle made of two or more atoms joined together.
- Ion — Atom or molecule with an electric charge.
- Lattice — Regular, repeating particle arrangement in solids.
- Brownian motion — Random movement of particles suspended in a fluid due to collisions.
- Diffusion — Mixing and spreading out of particles from regions of high to low concentration.
- Kinetic theory — Explanation of matter behavior based on particle movement and energy.
Action Items / Next Steps
- Review experimental techniques on measurement and method of purification for the next lesson.