1. Physical and Chemical Changes Betsy Sanford Barber Middle School 8 th Grade Physical Science

2. 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)

3. 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

4. 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)

5. 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

6. 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

7. 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

8. 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

9. 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.

10. Energy…  …is required for both types of changes