Changes in Matter ISCI 2002 Chapter 11

Phases of Matter Solid (s) ------ Liquid (l) --------- Gas (g) Phases: ‘physical state’ Solids Definite volume and shape Liquids Definite volume, but form determined by container it is in Gases No definite volume or shape

Submicroscopic Level Solids Liquids Gases Strong attraction between molecules- fixed position (vibrate) Heat breaks fixed arrangement Liquids Molecules ‘flow’ Gases Heat causes attractions between individual molecules to be broken Move in random manner Bump into the container – ‘pressure’

Diffusion Gas molecules continue to move and bump into each other Move from higher concentration areas to lower areas of concentration Occurs in: Gases, liquids Diffusion Animation

Phase Changes Animation

Process of Evaporation Molecules are heated below the surface, gain kinetic energy and bump into molecules at the surface Surface molecules are released (attraction to other molecules broken) Why is this a cooling process? The slower moving molecules left behind (lower temperature) cools the air or body (perspiration)

Condensation This is a warming process Why? Gas particles cool and reach the surface. Kinetic energy absorbed by surface molecules. Molecules form attractions This increases temperature

Chemical and Physical Properties Appearance – hard or soft; dull or shiny; color Density; melting point and boiling point Chemical Properties- describes changes of composition the substance undergo’s during a chemical change What is required to bring about the change Temperature, heat, number of electrons, etc.

Chemical and Physical Properties Extensive Property Depends on the ‘quantity’ of matter in a sample Cannot be used to characterize a type of matter Mass of water is 2.0 kg? Another sample may be 4.0 kg Volume, mass Intensive Property (distinguishes one substance from another) Property shared by all examples of a specific type of matter Density (m/v); color; melting point; solubility; acidic or alkaline The density of water is 1.0 g/cm3

Physical and Chemical Properties Physical change: a change in the physical properties of a substance. Chemical change: the transformation of one or more substances into others. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley