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 • 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 • Gasmolecules continue to move and bump into each other • Move from higherconcentration areas to lowerareasofconcentration • 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 • Surfacemolecules are released (attraction to other molecules broken) • Why is this a coolingprocess? • The slower moving molecules left behind (lower temperature) cools the air or body (perspiration)
Condensation • This is a warming process • Why? • Gasparticlescool and reach the surface. Kinetic energy absorbed by surface molecules. Molecules form attractions • This increases temperature
Chemical and Physical Properties • PhysicalProperties • Appearance – hard or soft; dull or shiny; color • Density; melting point and boiling point • ChemicalProperties-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 • ExtensiveProperty • 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 • IntensiveProperty (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 • Physicalchange: a change in the physical properties of a substance. • Chemicalchange: the transformation of one or more substances into others.