Physical and Chemical Changes

Physical Property  Observable traits that do not change the identity of the substance  Include color, shape, smell, taste, mass, volume and density  Also include ductility, malleability, conductivity and solubility  Can be determined without changing a substance

Physical Property  Density - mass/volume  Ductility – ability to be pulled into wire  Malleability – ability to be hammered  Conductivity – ability to pass electric current  Solubility – ability to dissolve

Physical Change  Any change in size, shape, form, or state where the identity of the matter stays the same  Ex. - Cutting a watermelon into slices  Often easy to reverse with filtration, magnetism, evaporation, distillation, and centrifuge

Physical Change  Evidence includes: same substance no new substances color change state change same smell, taste, texture different volume, mass same density

Chemical Property  The characteristic of a substance that allows it to change into something different  Includes flammability, reactivity with oxygen, and acidity  Testing for chemical properties causes a change in the substance

Chemical Property  Flammability – able to be burned; combustion  Reactivity with oxygen  Acidity pH level scale from 1 to 14 1 being most acidic 14 being least acidic (most basic) Water is a 7 (neutral) on the pH scale

Chemical Change  Happens when a substance undergoes a change that causes it traits to change  Ex. - digestion, photosynthesis, paint drying, and oil burning.  New materials are formed that are different from the starting materials

Chemical Change  NOT easily reversed  Evidence includes: Release of energy – light, heat, sound Formation of gas or solid that is NOT the results of simple state change

Chemical Change  Evidence includes: new substance

Example of Chemical Change  Chlorine Added to swimming pools and drinking water Causes acidity Prevents reproduction, growth and development of algae, bacteria, protists and insects.

Types of Chemical Reactions  Synthesis  Decomposition

Acids and Bases  Acids Sharp smell, sour taste Corrode metals, harmful to organisms pH between 0 and 7 Ex. - citrus fruits contain acids.  Bases Feel slippery, taste bitter May also be harmful to organisms pH of between 7 and 14 Ex. - a bar of soap is basic

Salts  Salts are compounds of metal and nonmetal  Formed when acids and bases react  Ex. – table salt and chalk

Energy…  …is required for both types of changes