Physical and Chemical Changes Physical Property Observable traits
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: l l l l 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 ¡ l l l p. H level scale from 1 to 14 1 being most acidic 14 being least acidic (most basic) Water is a 7 (neutral) on the p. H 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: ¡ l l Release of energy – light, heat, sound Formation of gas or solid that is NOT the results of simple state change
Chemical Change ¡ Evidence includes: l new substance
Example of Chemical Change ¡ Chlorine l l l 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 l l ¡ Sharp smell, sour taste Corrode metals, harmful to organisms p. H between 0 and 7 Ex. - citrus fruits contain acids. Bases l l Feel slippery, taste bitter May also be harmful to organisms p. H of between 7 and 14 Ex. - a bar of soap is basic
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
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