Physical and Chemical Changes

Physical Changes  Changes the appearance but not the identity of the substance.  Examples:  Folding a sheet of paper  Breaking a piece of wood in half  Bend a paper clip  Ice melting  Water boiling

Chemical Changes  The key characteristic of a chemical reaction is the production of new materials that are chemically different from the starting materials. Salt (NaCl) Na (Sodium): Highly reactive Metal Cl (Chlorine): Poisonous Gas

Evidence of a Chemical Change 1.Volume Change: Increase or decrease without adding or taking away a substance. 2.Gas Given Off: Appearance or formation of bubbles without the addition of outside heat. 3.Formation of a Precipitate: Mixing of 2 solutions in which a solid forms.

4.Permanent Color change. 5.Change in Properties of Substances: Magnetic turns non-magnetic Poisonous turns non-poisonous Conductor becomes insulator 6.Evolution of Light. 7.Energy Change: Endothermic or exothermic, could be very slight and unnoticeable.