Physical and Chemical Changes

Betsy SanfordBarber Middle School8th Grade Physical Science

Physical Property

Observed traits Helps describe/classify substances Helps identify uses for substances

Can be seen or measured without changing a substance

Examples: color, shape, smell, taste measurements like mass, volume, density state (solid, liquid, gas)

Physical Property

More examples: Ductility - ability to be made

into wires Malleability - ability to be

shaped without breaking Conductivity - ability to carry

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

Example: cutting a watermelon into slices tearing up a sheet of paper sharpening a pencil

Often easy to reverse with: filtration, magnetism, evaporation,

distillation and centrifuge (spinning)

Physical Change

Evidence for a physical change: same substance before and after no new substances a color change a state change (solid, liquid, gas) same smell, taste, texture different volume, mass same density

Chemical Property

Helps describe/classify substances Helps identify uses for substances

Traits that allow a substance to change Testing for chemical properties causes a

change in the substance

Examples: Flammability - ability to catch fire reactivity with oxygen acidity - pH, reaction with hydrogen

Chemical Change

chemical change happens when a substance undergoes a change that causes its traits to change

new materials are formed that are different from the starting materials

Examples: digestion photosynthesis (plants making food) burning fuel

Chemical Change

NOT easily reversed

Evidence for a chemical change: more than one of the following occurs release of energy (light, heat, sound) formation of new substance (a gas or

solid that is not just a state change) color change odor change volume change

Chemical Change

Chlorine added to swimming pools and drinking

water causes acidity (change in pH) prevents reproduction, growth and

development of algae, bacteria, protists and insects.

Energy…

…is required for both types of changes