Presentation on theme: "Chemical Properties & Physical and Chemical Changes"— Presentation transcript:
1Chemical Properties & Physical and Chemical Changes
2Physical changes are those changes that do not result in the production of a new substance. If you melt a block of ice, you still have H2O at the end of the change.
3If you break a bottle, you still have glass If you break a bottle, you still have glass. Painting your nails will not stop them from being fingernails. Some common examples of physical changes are: melting, freezing, condensing, breaking, crushing, cutting, and bending.
4When a change of state occurs, molecules or atoms may movefaster or slower, may spread outor clump together, but they do notchange.i.e. An H2O molecule is still an H2O molecule!
5Some, but not all physical changes can be reversed Some, but not all physical changes can be reversed. You could refreeze the water into ice, but you cannot put your hair back together if you don’t like your haircut!
6Special types of physical changes where any object changes state, such as when water freezes or evaporates, are sometimes called change of state operations.
7The distinction between physical and chemical change. Physical changeA substance alters its physical form, not its compositionChemical changeA substance is converted into a new substance
8Lithium (Li) is a soft, gray solid that has the lowest density Sample Problem 1.5Calculating Density from Mass and LengthPROBLEM:Lithium (Li) is a soft, gray solid that has the lowest densityof any metal. If a slab of Li weighs 1.49 x 103 mg and hassides that measure 20.9 mm by 11.1 mm by 11.9 mm, what is the density of Li in g/cm3 ?
10CHEMICAL PROPERTIESChemical properties can ONLY be observed AS the substances are changing into different substances.
11Chemical changes, or chemical reactions, are changes that result in the production of a new substance.
12FLAMMABILITY: A material’s ability to BURN in the presence of OXYGEN A chemical property
13REACTIVITY: How readily (easily) a substance combines chemically with other substances. A chemical property
14Some Characteristic Properties of Copper Table 1.1Some Characteristic Properties of CopperPhysical PropertiesChemical Propertiesslowly forms a basic blue-greensulfate in moist airreddish brown, metallic lustereasily shaped into sheets(malleable) and wires(ductile)reacts with nitric acidand sulfuric acidgood conductor of heatand electricitydensity = 8.95 g/cm3slowly form a deep-bluesolution in aqueous ammoniamelting point = 10830Cboiling point = 25700C
15When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon. When you light your Bunsen burner in lab, you are carrying out a chemical reaction that produces water and carbon dioxide.
16Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, burning, and decomposition.
17Physical or Chemical Change? Painting WoodPHYSICAL
18Physical or Chemical Change? Burning PaperCHEMICAL
19Physical or Chemical Change? Digestion of foodCHEMICAL
20Sugar dissolving in water PHYSICAL Physical or Chemical Change?Sugar dissolving in waterPHYSICAL
21Iron turning red when heated PHYSICAL Physical or Chemical Change?Iron turning red when heatedPHYSICAL
22Physical or Chemical Change? EvaporationPHYSICAL
23A pond freezing in winter PHYSICAL Physical or Chemical Change?A pond freezing in winterPHYSICAL
24Physical or Chemical Change? Melting icePHYSICAL
25Physical or Chemical Change? Cutting wirePHYSICAL
26Physical or Chemical Change? Painting fingernailsPHYSICAL
27Physical or Chemical Change? Cutting fabricPHYSICAL
28Physical or Chemical Change? Baking muffinsCHEMICAL
29Physical or Chemical Change? Shattering glassPHYSICAL
30Decomposition of old leaves CHEMICAL Physical or Chemical Change?Decomposition of old leavesCHEMICAL
31Physical or Chemical Change? Wrinkling a shirtPHYSICAL
32Physical or Chemical Change? An old nail rustingCHEMICAL
33Common Decimal Prefixes Used with SI Units Table 1.3
34Densities of Some Common Substances* Table 1.5Substance Physical State Density (g/cm3)HydrogenGasOxygenGasGrain alcoholLiquid0. 789WaterLiquid0.998Table saltSolid2.16AluminumSolid2.70LeadSolid11.3GoldSolid19.3*At room temperature(200C) and normal atmospheric pressure(1atm).
35Physical versus Chemical Properties Unit II - Part 1The study of matter35
36Reviewing MATTER Matter: anything that has mass and takes up space Mass – the amount of matter in somethingVolume – the amount of space something occupiesWhich of the following is matter?A car?A box?You?36
37What is a property?Property: a characteristic of a substance that can be observed37
38Physical PropertyPhysical property: a property that can be observed without changing the identity of the substance.Examples:lustermalleability: the ability to be hammered into a thin sheetductility: the ability to be stretched into a wiremelting pointboiling pointdensitysolubilityspecific heat38
39• In a physical change no new substances are formed• Physical changes include changes ofstate.• liquid to solid: Solidifying or Freezing• solid to liquid: Melting• liquid to gas: Evaporation or Boiling• gas to liquid: Condensation• gas to solid or solid to gas: Sublimation
40Special Physical Properties Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressurewater = 0oCBoiling point: the temperature at which a substance changes from a liquid to a gas at a given pressurewater = 100oC40
41Chemical PropertiesChemical property: a property that can only be observed by changing the identity of the substanceExamples:flammabilityability to rustreactivity with vinegar41
42Density Density is the amount of mass per unit of volume. Density can be used to identify a substance.The density of water is 1.0g/mL42
43Density Calculations Calculations: D = m/V = g/mL = g/cm3Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water?Mass = 2.8 g Volume = 3.67 mLD = 2.8g/3.67 mL= 0.76 g/mLThis object would float in water because its density is less than water (1.0 g/mL).43
44More Density Calculations Ex: A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance.M=25.6 g V=31.6 mLD = 25.6 g/31.6 mLD= 0.81 g/mLThe substance is ethanol.44
45Rules for Rounding Off Numbers 1. If the digit removed is more than 5, the preceding number increases by 1.5.379 rounds to 5.38 if three significant figures are retained and to 5.4 if two significant figures are retained.2. If the digit removed is less than 5, the preceding number is unchanged.rounds to if three significant figures are retained and to 0.24 if two significant figures are retained.3.If the digit removed is 5, the preceding number increases by 1 if it is odd and remains unchanged if it is even.17.75 rounds to 17.8, but rounds to 17.6.If the 5 is followed only by zeros, rule 3 is followed; if the 5 is followed by nonzeros, rule 1 is followed:rounds to 17.6, but rounds to 17.74. Be sure to carry two or more additional significant figures through a multistep calculation and round off only the final answer.
46Clues that a Chemical Change has occurred. • Color change• Heat or light given off• Odor given off• Gas released• Solid forming in a liquid