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CHAPTER :MATTER & ENERGY Homework # 1
Physical VS Chemical Properties WS (online) TOMORROW: TEST
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9/28 AIM # 1: How are physical changes differentiated from chemical changes?
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What is a property? Property is a characteristic of a substance that can be observed.
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1. Intensive and Extensive Properties
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A. Intensive Property: Do not depend on the size of the sample
A. Intensive Property: Do not depend on the size of the sample. An intensive property doesn't change when you take away some of the sample Color Electrical conductivity Boiling point and melting point Ductility Taste Luster Hardness Density Solubility Malleability Specific heat
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B. Extensive Property Depend on the size of the sample.
An extensive property is a property that changes when the size of the sample changes Mass Volume Length Shape
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2. Physical Properties Physical properties of a substance are those characteristics that can be observed without the production of new substances.
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Copper 29Cu Metal, conducts electricity, ductile (can be drawn into wires), malleable, and metallic luster.
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Sulfur 16S Nonmetals, do not conduct electricity, yellow color, brittle (breaks easily).
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Oxygen O2 Nonmetal, gas, colorless, odorless, slightly denser than air, slightly soluble in water.
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3. Chemical Properties Chemical properties of a substance are those characteristics that describe how the substance interact (or fails to interact) with other substances to produce new substances.
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Oxygen Does not burn Supports combustion
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4. Physical Change Physical change is a change in form or state without a change in composition.
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crushing a can melting ice cube boiling water mixing sand and water breaking a glass dissolving sugar and water shredding paper chopping wood mixing red and green marbles sublimating (dry ice)
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Sublimation: CO2(s) CO2(g)
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Sublimation: I2(s) I2(g)
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Physical Change
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Grind Coffee
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whipping egg whites (air is forced into the fluid, but no new substance is produced)
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Boiling Water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.)
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Dissolving Sugar in Water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.)
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Dicing Potatoes (cutting usually separates molecules without changing them.)
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5. Chemical Change Chemical change is one in which a substance loses the properties by which we recognize it and produces a new substance.
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How do you know when a chemical reaction is taking place?
8F Signs of a chemical reaction How do you know when a chemical reaction is taking place? gives out a gas glows color changes Light heats up cools down flashes produces smoke Precipitate (solid)
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Example The burning of paper Sugar + heat
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Chemical change
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Chemical Change
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Iron Rusting
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Color Change You have just witnessed a spectacular chemical change if you have seen the leaves change color in the autumn.
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Spring
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Another sign of a chemical change is the release or gain of energy by an object.
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Release of Heat and Light
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Release of Energy (heat and light)
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Odor Changes It only takes one experience with a rotten egg to learn that they smell different that fresh eggs. When eggs and food spoil, they undergo a chemical change. The change in odor is a clue to the chemical change
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Production of Gases Zn metal reacting with Hydrochloric Acid
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Copper Metal Reacting with Nitric Acid
Production of Gases Copper Metal Reacting with Nitric Acid
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Production of Solids Pb(NO3)2 + KI <-> PbI2 + KNO3
Lead (II) Potassium Lead (II) Potassiun nitrate iodide iodide nitrate
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Not Easily Reversed
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Questions
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1. Water boils at 100 degrees Celcius.
physical property.
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2. Diamonds are capable of cutting glass.
physical property. .
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3. Sugar is capable of dissolving in water.
physical property.
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4. Vinegar will react with baking soda.
chemical property.
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5. Yeast acts on sugar to form carbon dioxide and ethanol.
chemical property.
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5. Wood is flammable. chemical property.
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6. Aluminum has a low density.
physical property.
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7. Ammonia is a gas at room temperature.
physical property.
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8. Bromine has a red color. This is a physical property.
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9. Dry ice, solid carbon dioxide, is sublimed at room temperature.
physical change. Sublimation: solid to gas
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10. Salt is dissolved in water.
physical change.
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11. Iron rusts in a damp environment.
chemical change.
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12. Gasoline burns in the presence of oxygen.
chemical change.
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13. Hydrogen peroxide decomposes to water and oxygen.
chemical change.
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End of the show!
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iron rusting (iron oxide forms)
gasoline burning (water vapor and carbon dioxide form) eggs cooking (fluid protein molecules uncoil and crosslink to form a network) bread rising (yeast converts carbohydrates into carbon dioxide gas) milk souring (sour-tasting lactic acid is produced) Sun tanning (vitamin D and melanin is produced)
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