Kinetic Molecular Theory and States of Matter

Kinetic Theory of Matter Particles (molecules) are in constant motion The amount of kinetic energy determines the phase of the sample Temperature is a measure of average kinetic energy High kinetic energy = faster movement and bigger movement of particles Large distances between gas particles makes attractions between particles unimportant Strong attractions in solid and liquid phases make samples dense, not compressible

The Kinetic Theory 1. All matter is composed of small particles (atoms, molecules, or ions). 2. They are in constant, random motion. 3. They constantly collide with each other and with the walls of their container.

Thermal E x p a n s i o n Particles in any state expand when heated Expansion joints (solid) Mercury is a liquid that expands in thermometers Air expands when heated (becoming less dense)

STATES OF MATTER Defined by particle arrangement Defined by kinetic energy of particles Defined by distance between particles

Solids Fixed Volume Fixed Shape Not Compressible Very Dense Particles are tightly packed in an orderly arrangement, little space between particles Very strong forces of attraction between particles Particles vibrate about a fixed position Lowest energy particles

Liquids Fixed Volume Take the shape of the container Not Compressible Dense Particles are closely packed in a disorderly arrangement, spacing is far enough to slide past Strong forces of attraction between particles Particles can move past one another; Liquids flow Middle energy particles

Gases Not Fixed Volume Take the shape of the container Easily Compressible Not Dense Particles are far apart in random arrangement Forces of attraction between particles are negligible Particles move about randomly at high speed Highest energy particles

STATES OF MATTER LIQUID PLASMA SOLID GAS Tightly packed, in a regular pattern Vibrate, but do not move from place to place Close together with no regular arrangement. Vibrate, move about, and slide past each other Well separated with no regular arrangement. Vibrate and move freely at high speeds Has no definite volume or shape and is composed of electrical charged particles

Phase Changes

Energy of Phase Changes

Phase Change Diagram

Phase Diagrams

Phase Diagram

Learning Check Identify the solid, liquid, and gas phases on the phase diagram.

Learning Check What are the melting point and the boiling point of the substance at 1atm?

Learning Check What phase is the sample at 1 atm and 110oC?

Learning Check What would cause the sample to change from a liquid to the solid phase at constant temperature?

Temperature and Phase Changes What happens to the temperature of the sample during a phase change?

Thermodynamic Properties