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

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Presentation on theme: "Science AHSGE Standard II Objective 4- Physical and Chemical Changes."— Presentation transcript:

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

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