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Basic Concepts in Chemistry Physical Properties. Physical Properties A characteristic of a substance that you can observe and measure without changing.

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Presentation on theme: "Basic Concepts in Chemistry Physical Properties. Physical Properties A characteristic of a substance that you can observe and measure without changing."— Presentation transcript:

1 Basic Concepts in Chemistry Physical Properties

2 Physical Properties A characteristic of a substance that you can observe and measure without changing the identity of the substance.

3 Number vs. Quantity Quantity - number + unit UNITS MATTER!! Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

4 Types of measurement Quantitative- can be measured and assigned a particular value. use numbers to describe - melting point - viscosity is a measure of how easily a fluid flows. - 4 meters, - 100 0 C Qualitative- can be observed and described without detailed measurements. - the colour of aluminum is grey. -Hydrogen sulfide has a characteristic odour of rotten eggs. -Greenish-yellow gas could be a warning that chlorine gas is present. - extra large - hot

5 Scientists prefer Quantitative Quantitative - easy to check Easy to agree upon, no personal bias The measuring instrument limits how good the measurement is.

6 Examples of Qualitative Physical Properties PropertyExamples ColourColourless, red, black OdourSweet, pungent, mouldy StateSolid, liquid, or gas TextureRough, smooth, bumpy LustreShiny, dull malleabilitySoft, pliable, hard

7 Quantitative Physical Properties PropertyDescription ViscosityResistance to flow Melting pointTemperature of melting Boiling pointTemperature of boiling SolubilityAbility to dissolve in another substance HardnessAbility to scratch another material ConductivityAbility to conduct electricity or heat DensityRatio of mass to volume

8 States of Matter

9 Gas, Liquid, and Solid Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 441 Gas Liquid Solid

10 Some Properties of Solids, Liquids, and Gases Property Solid Liquid Gas Shape Has definite shapeTakes the shape of Takes the shape the container of its container Volume Has a definite volumeHas a definite volume Fills the volume of the container Arrangement of Fixed, very closeRandom, close Random, far apart Particles Interactions between Very strongStrong Essentially none particles

11 To evaporate, molecules must have sufficient energy to break Intermolecular (IM) forces. Change of state from a liquid to a gas. Molecules at the surface break away and become gas. Only those with enough Kinetic energy (KE) escape. endothermicBreaking IM forces requires energy. The process of evaporation is endothermic. Evaporation is a cooling process. It requires heat. Evaporation

12 Change from gas to liquid Achieves a dynamic equilibrium with vaporization in a closed system. What is a closed system? A closed system means matter can’t go in or out. (put a cork in it) Condensation

13 Energy Changes Accompanying Phase Changes Solid Liquid Gas Melting Freezing Deposition CondensationVaporization Sublimation Energy of system Brown, LeMay, Bursten, Chemistry  2000, page 405

14 Melting / Boiling Point Boiling point of water Freezing point of water Absolute zero Celsius 100 Celsius degrees 100 o C 0oC0oC -273 o C Melting Point - change of state from solid to liquid Melting point: the temperature at which a solid turns into a liquid. Boiling point: the temperature at which a liquid turns into a gas. Boiling point of water is 100 0 C.

15 Chemical Stewardship Solutions

16 Definitions Solution -Solution - homogeneous mixture Solvent Solvent - present in greater amount Solute Solute - substance being dissolved

17 Definitions Solution -Solution - homogeneous mixture Solvent Solvent - present in greater amount Solute Solute - substance being dissolved

18 Solutions What the solute and the solvent are determines –whether a substance will dissolve. –how much will dissolve. A substance dissolves faster if it is stirred or –The particles are made smaller. shaken. –The temperature is increased. Why?

19 Solution = Solute + Solvent Solute - gets dissolved Solvent- does the dissolving –A–Aqueous (water) –T–Tincture (alcohol) –A–Amalgam (mercury) –O–Organic Polar Non-polar Dental filling Nightmare on White Street Chem Matters, December 1996

20 Solution Definitions solution: alloy: solvent: the substance that dissolves the solute watersalt a homogeneous mixture -- evenly mixed at the particle level -- e.g., salt water a solid solution of metals -- e.g., bronze = Cu + Sn; brass = Cu + Zn “will dissolve in” refers to two gases or two liquids that form a solution; more specific than “soluble” -- e.g., food coloring and water miscible: soluble:

21 Types of Solutions SoluteSolventSolution Gaseous Solutions gas liquid gas air (nitrogen, oxygen, argon gases) humid air (water vapor in air) Liquid Solutions gas liquid solid liquid carbonated drinks (CO 2 in water) vinegar (CH 3 COOH in water) salt water (NaCl in water) Solid Solutions liquid solid dental amalgam (Hg in Ag) sterling silver (Cu in Ag) Charles H.Corwin, Introductory Chemistry 2005, page 369

22 As size, rate As T o, rate 3. mixing Factors Affecting the Rate of Dissolution 1. temperature 2. particle size 4. nature of solvent or solute More mixing, rate

23 Classes of Solutions aqueous solution: water = “the universal solvent” solvent = water amalgam:solvent = Hg e.g., dental amalgam tincture:solvent = alcohol e.g., tincture of iodine (for cuts) organic solution:solvent contains carbon e.g., gasoline, benzene, toluene, hexane

24 Non-Solution Definitions insoluble:“will NOT dissolve in” e.g., sand and water immiscible:refers to two gases or two liquids that will NOT form a solution e.g., water and oil suspension:appears uniform while being stirred, but settles over time

25 Solubility Water HOT A B AFTER Before Water COLD Water HOT Add 1 drop of red food coloring Miscible – “mixable” two gases or two liquids that mix evenly Experiment 1: Water COLD A B

26 Solubility Water Oil T 30 sec AFTER Before Add oil to water and shake Immiscible – “does not mix” two liquids or two gases that DO NOT MIX Experiment 2: T 0 sec

27 Solubility vs. Temperature Timberlake, Chemistry 7 th Edition, page 297 KI NaNO 3 KNO 3 Na 3 PO 4 NaCl Temperature ( o C) Solubility (g solute / 100 g H 2 O) 200 180 160 140 120 100 80 60 40 20 0 406080100

28 Pure water does not conduct an electric current Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 215 Source of electric power Pure water

29 Ionic Solutions conduct a Current Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 215 Source of electric power Free ions present in water

30 Electrolytes Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. (a) Nonelectrolyte (b) Weak electrolyte (c) Strong electrolyte

31 Electrolytes Timberlake, Chemistry 7 th Edition, page 290 Electrolytes Electrolytes - solutions that carry an electric current NaCl(aq) Na + + Cl - HF(aq) H + + F - strong electrolyteweak electrolytenonelectrolyte

32 Solubility and the Environment Chemical Stewardship Be responsible in how you dispose of and use chemicals. Chemical pollution can travel far – and harm organisms. Frog with three legs – it has mutated from chemical exposure.

33 Early Warning Signs… = Contamination of water where frog lives causes mutations. Canary dies in the mine from bad air (cyanide). This is clue for miners to leave the mine…alive.

34 Pfiesteria Fish sores from infection by pfiesteria. Pfiesteria organism

35 We all use Chemical Solutions Average Family spends: $ _________ / year on chemical solutions? Make-up, laundry detergent, motor oil, gasoline, food preservatives, deodorant, lawn fertilizers & weed killers, shampoo, air fresheners, floor wax, furniture polish, toothpaste, mouthwash, oven cleaner, glass cleaner, etc… 1200

36 Solvents Solvents at the hardware store

37 Density Density is an INTENSIVE INTENSIVE property of matter. - does NOT depend on quantity of matter. - color, melting point, boiling point, odor, density Contrast with EXTENSIVE - depends on quantity of matter. - mass, volume, heat content (calories) Styrofoam Brick

38 StyrofoamBrick ? It appears that the brick is ~40x more dense than the Styrofoam.

39 M M M M V V == D D V V D D Brick Styrofoam Brick

40 Which liquid has the highest density? 5 2 3 1 4 Coussement, DeSchepper, et al., Brain Strains Power Puzzles  2002, page 16 least dense 1 < 3 < 5 < 2 < 4 most dense

41 Cube Representations 1 m 3 = 1 000 000 cm 3 Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 119

42 Volume and Density Relationship Between Volume and Density for Identical Masses of Common Substances Cube of substance Mass Volume Density Substance (face shown actual size) (g) (cm 3 ) (g/cm 3 ) Lithium Water Aluminum Lead 10 19 0.53 10 10 1.0 10 3.7 2.7 10 0.58 11.4

43 Density D M V ensity ass olume D = MVMV M = D x V V = MDMD

44 Volume Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41 6 cm 3 cm 2 cm 1 cm 4 cm

45 2 cm Volume Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41 V = length x width x height V = 2 cm x 2 cm x 2 cm V = 8 cm 3 Volume = length x width x height Volume = 6 cm x 2 cm x 3 cm 6 cm 3 cm 2 cm 1 cm 4 cm Volume = 36 cm 3 Volume = Volume = 28 cm 3 8 cm 3 -

46 Density of Some Common Substances Density of Some Common Substance Substance Density (g / cm 3 ) Air 0.0013* Lithium 0.53 Ice 0.917 Water 1.00 Aluminum 2.70 Iron 7.86 Lead 11.4 Gold 19.3 Density of Some Common Substance Substance Density (g / cm 3 ) Air 0.0013* Lithium 0.53 Ice 0.917 Water 1.00 Aluminum 2.70 Iron 7.86 Lead 11.4 Gold 19.3 *at 0 o C and 1 atm pressure

47 Consider Equal Volumes The more massive object (the gold cube) has the _________ density. Equal volumes… …but unequal masses aluminum gold GREATER Density = Mass Volume Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 71

48 Consider Equal Masses Equal masses… …but unequal volumes. The object with the larger volume (aluminum cube) has the density. aluminum gold Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 71 smaller Christopherson Scales

49 Consider Equal Masses Equal masses… …but unequal volumes. The object with the larger volume (aluminum cube) has the density. aluminum gold Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 71 smaller Christopherson Scales

50 Two ways of viewing density Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 71 Equal volumes… …but unequal masses The more massive object (the gold cube) has the greater density. aluminum gold (A) Equal masses… …but unequal volumes. (B) gold aluminum The object with the larger volume (aluminum cube) has the smaller density.

51 O 2- H+H+ H+H+ H2OH2O  ++ ++ Water Molecule Water is a POLAR molecule

52 Water Molecule O 2- H+H+ H+H+ Water is a POLAR molecule H2OH2O  ++ ++ Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 8

53 Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. Water molecules “stick” together to create surface tension to support light weight objects.

54 Water Molecule What is a polar molecule? How does the polarity of water effect this molecule? O H H Hydrogen bond  

55 Hydrogen bonds occur between two polar molecules, or between different polar regions of one large macro- molecule. One “relatively” negative region is attracted to a second “relatively” positive region. O H H H N H H Electronegative atoms Hydrogen bond

56 Reviewing Concepts Reviewing Concepts Physical Properties List seven examples of physical properties. Describe three uses of physical properties. Name two processes that are used to separate mixtures. When you describe a liquid as thick, are you saying that it has a high or low viscosity?

57 Reviewing Concepts Reviewing Concepts Physical Properties Explain why sharpening a pencil is an example of a physical change. What allows a mixture to be separated by distillation?


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