1. Science AHSGE Standard II Objective 4- Physical and Chemical Changes

2. The Law of Conservation of Matter Matter can neither be created nor destroyed, only transformed from one form to another –These transformations can be physical changes or chemical changes

3. Physical Change A change in the appearance of a substance Still the same substance –Mixture- Physically combining substances without altering either Can take back apart Solution- Mixture of a solute and solvent –Solvent- Substance dissolving a solute –Solute- Substance being dissolved in a solvent Typically, changes in the state of matter Brought on by a change in temperature

4. Physical Changes Freezing- Liquid to solid –Freezing point- temperature at which a substance will freeze 0° Celsius; 32° Farenheit or below Melting- Solid to liquid –Melting point- temperature at which a substance will melt 0° Celsius; 32° Farenheit or above

5. Physical Changes Evaporation- Liquid to gas –Boiling- Forced evaporation by adding heat Boiling point- Temperature at which a substance will boil –100° Celsius; 212° Fareinheit

6. Physical Changes Condensation- Gas to liquid –Due to temperature changes –Ex: Water on windows in the morning Sublimation- Solid to gas –Ex: Moth balls, potpourri

7. Physical Changes Distillation- Change from a liquid to gas and back to a liquid –Purifies (cleans) liquid –Commonly done for water and alcoholic beverages

8. Chemical Changes A change in matter that results in a different substance Changes appearance and chemical properties Can not mechanically separate back to original substances Usually accompanied by a change in energy Often gives off heat and/or light Compounds- Chemically combined elements bonded together –Compounds can be separated or built to form new substances –Ex: 2H 2 O 2H 2 + O 2 Water separates into hydrogen and oxygen gas or vice versa

9. Chemical Changes Combustion- Chemical process converting chemical energy into heat and light energy –Ex: Burning –Anywhere theres smoke, theres combustion –Anything that can burn has chemical energy

10. Chemical Changes Fermentation- Partial breakdown of a substance due to a lack of oxygen –Ex: Carbon dioxide escaping fallen fruit, creating alcohol

11. Chemical Changes Electrolysis- Decomposition of a substance by use of electrical current –Ex: Breakdown of water by attracting hydrogen and oxygen gas to opposite terminals of a battery

12. Rate of Reactions Inhibitor- Any substance that slows or stops a reaction Catalyst- Any substance that speeds up a reaction –Ex: Water speeds up the rusting process water Iron + Oxygen Iron oxide (rust) –Enzyme- Special type of catalyst that lowers the activation energy required to start a reaction; starts faster Found in stomach and in cell lysosomes The greater the surface area of a substance, the faster it reacts –Smaller substances have greater surface area than larger substances –Ex: Sugar grain will dissolve faster than a sugar cube Increase in temperature, increases reaction rates Increase in concentration (amount) of solvents increases reaction rate Stirring or shaking increases reaction rate