3.1 Properties of Matter 3.2 Changes in Matter 3.3 Mixtures of Matter - PowerPoint PPT Presentation

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3.1 Properties of Matter 3.2 Changes in Matter 3.3 Mixtures of Matter
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3.1 Properties of Matter 3.2 Changes in Matter 3.3 Mixtures of Matter

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  1. Chapt 3 Matter – Properties & Change • 3.1 Properties of Matter • 3.2 Changes in Matter • 3.3 Mixtures of Matter • 3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

  2. Section 3.1 Properties of Matter Most common substances exist as solids, liquids, and gases, which have diverse physical and chemical properties. • Identify the characteristics of a substance. • Distinguish between physical and chemical properties and changes and be able to give examples of each. • Distinguish between intensive and extensive physical properties and be able to give examples of each type. • Differentiate among the physical states of matter; know the meaning of the term “vapor”.

  3. Section 3.1 Properties of Matter Key Concepts • The three common states of matter are solid, liquid, and gas. Physical properties can be observed without altering a substance’s composition. • Chemical properties describe a substance’s ability to combine with or change into one or more new substances. • External conditions can affect both physical and chemical properties.

  4. Substance • Matter that has a uniform and unchanging composition (aka pure substance) • Copper (Cu – an element) • Salt (sodium chloride, NaCl) • Dionized water (H2O) • Any matter that is not a pure substance is a mixture – see section 3.3 • Tap water (has dissolved minerals)

  5. States of Matter • Solid - Definite shape and volume • Liquid -Flows, constant V, takes shape of its container • Gas - Conforms to and fills entire volume of container • Vapor – gaseous state of room temperature solid/liquid

  6. Physical Properties • Can be observed or measured without changing samples composition • Density Color Luster Hardness • Conductivity Melting/boiling points

  7. Physical Properties of Common Substances – Table 3.1

  8. Extensive/Intensive Properties • Extensive – dependent upon amount of substance present Mass Length Volume • Intensive – not dependent upon amount Density Pressure Temperature • Ignore book example re: scent & spices

  9. Chemical Property • Ability of a substance to combine with or change into one or more other substances

  10. Properties of Cu – Table 3.2 Note distinctions between physical and chemical properties

  11. Practice Problem 3 page 75 Classify each of the following as [being related to] a physical or a chemical property: chem • Iron and oxygen form rust • Iron is more dense than aluminum • Magnesium burns when ignited • Oil and water don’t mix • Mercury melts at 39 C phys chem phys phys

  12. Chapt 3 Matter – Properties & Change • 3.1 Properties of Matter • 3.2 Changes in Matter • 3.3 Mixtures of Matter • 3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

  13. Section 3.2 Changes in Matter Matter can undergo physical and chemical changes. • Define physical change and list several common physical changes. • Define chemical change and list several indications that a chemical change has taken place. • Apply the law of conservation of mass to chemical reactions.

  14. Section 3.2 Changes in Matter Key Concepts • A physical change alters the physical properties of a substance without changing its composition. A chemical change, also known as a chemical reaction, involves a change in a substance’s composition. • In a chemical reaction, reactants form products. • The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction; it is conserved. • massreactants= massproducts

  15. Physical Properties and Changes • Changes don’t alter chemical nature • Changes in shape from applied mechanical forces • Cut, bend, crumple • Phase changes • Melting, boiling, condensation, freezing • Melting and boiling points (see table 3.1) are intensive physical properties useful in identifying a substance

  16. Chemical Changes • In a chemical change (reaction), reactants (R) form products (P) • R  P • New Substances Created • Rusting – Iron (R) to iron oxide (P) • Fermentation – sugar (R) to alcohol (P) • Combustion – methane (R) to CO2 (P) and H2O (P)

  17. Evidence of Chemical Change • Rusting; properties that change include: • Color: metallic grey  brownish orange • Attracted to magnet: yes  no • Chemical reaction always produces a change in properties

  18. Conservation of Mass • Mass is neither created or destroyed in a chemical reaction; it is conserved • Mass reactants = Mass products • Lavoisier (1743-1794) credited with concept; studied thermal composition of mercury (II) oxide to mercury & oxygen • Proof of it depended on development of analytical balance capable of detecting small mass changes

  19. Thermal Decomposition of HgO Sum of masses of liquid mercury and gaseous oxygen products equal to original mass of mercury(II) oxide solid 2HgO(s)  2Hg(l) + O2(g)

  20. Conservation of Mass Example problem 3.1 page 78 10.00 g HgO heated to produce 9.26 g Hg Mass of oxygen formed in reaction? Knowns: mHgO = 10.00 g mHg = 9.26 g Unknown: mO2 ? mreactants = mproductsLaw of Conservation of Mass mHgO = mHg + mO2mO2 = mHgO mHg mO2 = 10.0 g  9.26 g = 0.74 g of oxygen 2HgO(s)  2Hg(l) + O2(g)

  21. Practice Conservation of mass Problems 5 – 9 page 78 Problems 13(a-b) page 79 Problems 50 – 55 pages 94 - 95

  22. Chapt 3 Matter – Properties & Change • 3.1 Properties of Matter • 3.2 Changes in Matter • 3.3 Mixtures of Matter • 3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

  23. Section 3.3 Mixtures of Matter Most everyday matter occurs as mixtures—combinations of two or more substances. Objectives • Define and distinguish between substances and mixtures. • Define and distinguish between homogeneous and heterogeneous mixtures and be able to give examples of each. • Classify and give examples of the seven different types of solutions (3 possible states for the solution and 3 combinations of phases of solute and solvent for the liquid and solid phase solutions).

  24. Section 3.3 Mixtures of Matter Objectives (cont) • Name and describe various mixture separation techniques and identify which technique would be most appropriate for a given separation problem. • Describe the role that mobile and stationary phases play in chromatographic separation techniques. • Describe how affinity differences play a role in liquid-liquid and chromatographic separation techniques. [material only partially in textbook]

  25. Section 3.3 Mixtures of Matter Key Concepts • A mixture is a physical blend of two or more pure substances in any proportion. • Solutions are homogeneous mixtures. • Mixtures can be separated by physical means. Common separation techniques include filtration, distillation, crystallization, sublimation, and chromatography.

  26. Matter – Classification Scheme

  27. Mixtures • Combination of two or more pure substances in which each pure substance retains its individual chemical properties • Composition variable • Number of possible mixtures is infinite • Most everyday matter occurs as mixture

  28. Mixtures - Types • Heterogeneous • Not smoothly blended [may appear to be just by looking at it but will not be at the microscopic level] • Individual substances remain distinct • Sand & water • Paint, mayonnaise [heterogeneous at a microscopic level – not all heterogeneous mixtures are readily identified as such by the naked eye]

  29. Mixtures - Types • Homogeneous • Constant composition throughout – even down to the microscopic level • Single phase (gas, liquid or solid) [although heterogeneous mixtures can also be a single phase such as a water/oil emulsion] • More commonly used term is solution • Salt & water

  30. Mixtures and CompoundsIron and Sulfur S Fe React chemically - cannot be separated by physical means Physically mixed - can be separated by physical means

  31. Solutions - Types • Table 3.3 “Types of Solution Systems” from the textbook; table 3.3 is not completely correct Liquid-gas example wrong – water droplets are 2nd phase (incompatible with definition of solution) Liquid-liquid example misleading – seawater itself is a solution of a solid dissolved in liquid water, so liquid is same for both; much better example is solution formed from 2 pure liquids, such as a solution of isopropyl alcohol in water (what you get from a drugstore)

  32. Solutions - Types • On the next slide is an expanded (and correct) version of Table 3.3 • 1st column is phase of solution itself • 2nd column is phase of solute – the “stuff” that is being dissolved in the solvent to form the solution • By definition there is less of the solute than there is of the solvent • 3rd column is phase of solvent • Can dissolve both gas & liquid in a solid!

  33. Types of Solutions

  34. Solutions • The following 3 slides are intended as examples of how common substances such as air and water can be more complicated than one might expect • You are not expected to know the actual compositions

  35. Composition of Dry Air (Solution)

  36. Layers of AtmosphereSolution with continuously variable composition Horizontally homogeneous (sort of – lots of point sources of pollutants) Vertically inhomogeneous but still a solution in local region

  37. Substances Found in Natural Waters Any natural water (tap or bottled) is a complicated homogeneous mixture (a solution) and if dust and sand/soil particles are counted, is a heterogeneous mixture

  38. Separating Mixtures • Take advantage of differing physical properties • Filtration – heterogeneous mixture • Solid from liquid • Distillation – typically liquid-liquid solutions; also solid-liquid (salt water) • Depends upon difference in boiling points • Most volatile (lower bp) material removed 1st • Crystallization – liquid-solid solutions • Remove enough solvent so solubility of solute exceeded – very high purity crystals possible

  39. Separating Mixtures • Sublimation (Phase change process in which solid changes directly into vapor) – can use in separation of solids if only one sublimates [extremely limited in actual practice] • Chromatography – separates components of mixture (mobile phase) based on ability of each component to travel across surface of another material (stationary phase) [this is most widely used separation technique in chemistry]

  40. Filtration Good for Solid/Liquid Separations

  41. Selective Crystallization When KNO3(s) crystallized from aqueous solution of KNO3 containing CuSO4 (blue) as an impurity, CuSO4 remains in solution KNO3 (white) crystallized from hot, saturated solution is virtually pure

  42. Zone Refining of Silicon Purification by Crystallization Heated (melted) zone moving left to right

  43. Simple Distillation Separation technique based on differences in boiling points (BPs) of substances involved – physical process, not chemical Distillation often synonymous with “simple” distillation; single evaporation followed by condensation of vapors Simple distillation - works well when BPs differ by ≥ 25 C (rule of thumb) Batch technique (single filling of apparatus)

  44. Gasoline vapors Condenser Gas Gasoline 38 oC Fractional Distillation of Crude Oil Kerosene 150 oC Heating oil 260 oC Lubricating oil 315 oC - 370 oC Crude oil from heater Steam Residue (asphalt, tar)

  45. Separating Mixtures • Forces exist between molecules • Details of molecular shape, size, and charge influence magnitude of force between any 2 molecules • For example, there are strong forces between oppositely charged molecules (ions)

  46. Separating Mixtures • Forces between certain types of molecules are stronger than than for other types of molecules • Ones with stronger forces said to have an affinity for each other • Can use affinity differences as basis for a separation technique

  47. Separating Mixtures - Partitioning • Solution with A & B dissolved in water • If A has higher affinity for another solvent than B does, can exploit to separate A & B • If water & 2nd solvent in contact, A will tend to concentrate in 2nd solvent • A & B said to partition between the 2 solvents – basis for liquid-liquid extraction process

  48. Liquid-Liquid Extraction Add 2nd immiscible (insoluble) solvent & shake Wait for partitioning, then drain off bottom 2 substances dissolved in water S2 S S S1 Separatory Funnel