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CLASSES OF MATTER

CLASSES OF MATTER. Chapter 3. Contrast and Compare. Classification Terms. Heterogeneous - made up of different parts / regions with different characteristics Homogeneous - same properties throughout. Perspective. Microscopic characteristics

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CLASSES OF MATTER

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  1. CLASSES OF MATTER Chapter 3

  2. Contrast and Compare

  3. Classification Terms • Heterogeneous - made up of different parts / regions with different characteristics • Homogeneous - same properties throughout

  4. Perspective • Microscopic characteristics • Normal Blood Cancerous Blood

  5. Perspective • Macroscopic characteristics • Blood from a crime scene

  6. Atom • Atom - the smallest component of an element having the chemical properties of the element 

  7. ELEMENT • Substance cannot be divided into anything simpler either physically, or chemically. • Sodium, copper and neon

  8. COMPOUND • Compound • Substance can be decomposed into 2 or simpler substances, AND • the simpler substances always occur in definite weight ratios. • + → Elemental Sodium Salt Crystal Compound ElementalChlorine

  9. H2O • Compound • ALWAYS has 2 hydrogen atoms which has a mass of 2, and 1 oxygen which has a mass of 16. • The mass ratio is thus 2:16, or 1:8

  10. MIXTURE • Two or more substances occur in any proportions AND • keep their own identifying characteristics AND • can be physically separated.

  11. Elements Known • 116 elements • 92 ‘pre Atomic Age’ elements • 2 that have never been found in nature • # 43 Tc Technetium [by product of Mo; used as a superconductor] • # 61 Pm Promethium [Rx of F or Cl w/ Group 1 metal; Glow in dark paint] • 2 found in extremely small quantities little known. • # 85 At Astatine • # 87 Fr Francium • 24 elements have been produced synthetically via nuclear reaction. • 1 element produced synthetically is now also thought to have once occurred naturally due to a recent scientific study (1998) • 94 Pu Plutonium

  12. PROPERTIES • A property is a characteristic or feature which can be used to aid in the identification of a substance.

  13. Physical Property • characteristic that can be identified w/o changing the substance chemically. • Extensive • Depends on the amt. present • length • volume . • mass • Intensive • independent of amt. present • melting pt • boiling pt. • color • density

  14. Chemical Property • Describes how, and if, one substance reacts w/ another. • Destructive • Original substance is chemically altered INACTIVE Some reactions ACTIVE Many reactions INERT No reactions

  15. Changes that Matter Undergoes • Physical Change • certain features of the substance are altered, but the chemical structure remains unchanged • cutting, changing shape, dissolving, melting, boiling • Chemical Change • results in new and different substances w/ different chemical and physical properties from the original substance • Burning, decomposing, digesting, rusting

  16. Indications of Chemical Change... • production of heat/light • production of electric current • production of a precipitate [a solid substance that forms when two liquids are combined.]

  17. ENERGY AND CHEMICAL CHANGE • Chemical rxn are always accompanied by some type of energy change. • In order for a chemical rxn to begin a certain amt. of energy must be invested to begin the rxn. • Activation energy

  18. ENERGY AND CHEMICAL CHANGE

  19. ENERGY AND CHEMICAL CHANGE • Energy • If the reaction produced more energy (heat) than it uses [nets energy] • Exergonic (Exothermic) reaction • If the reaction uses more energy (heat)than it releases • Endergonic (Endothermic) reaction

  20. DRIVING Nature • In all of nature there are only two major trends. • These trends oppose each other, and their balance governs nature. • These two trends determine which type of chemical reactions will occur and how strong those reactions will be.

  21. ENTROPY v. Ground State • chaos order • high temp low temp • endothermic rxn exothermic rxn • products absorb E products release E • unstable stable Entropy Ground State

  22. Dazzling Demos • Endo/Exothermic rxns. • Pickle nightlight • Carbon Soufflé • Instant Fire

  23. ENERGY CHANGES • Scientists are interested in measuring [quantifying] changes in energy that take place during chemical rxn. • Light produced - measure by a flash meter [intensity]; photographed • Electric current- ammeter measures the amps produced • Heat {most rxn}-measured by a calorimeter

  24. HEAT v TEMPERATURE • Heat - the TOTAL amount of kinetic E [energy of motion] present in a sample. • Heat = Total EK = Ea + Eb + Ec + Ed+ Ee+ Ef A C E D F B

  25. HEAT v TEMPERATURE • Temperature - The AVERAGE kinetic E present in a sample • Temperature = Average EK = Ea + Eb + Ec + Ed + Ee + Ef • 6 A D F C B E

  26. HEAT • More difficult to measure than temperature • Electrodes • Thermometer • Sample • Water • Calorimeter

  27. Heat • Measured in calorie or joule units • calorie - amount of heat needed to raise 1 g of water 1 oC. • 1 cal = 4.184 j • 1000 cal = 1 Cal

  28. Which produces the greater amount of heat energy? Which produces the greater temperature?

  29. Specific Heat • Specific Heat - the amount of heat required to raise the temperature of ANY substance 1 oC. • Reference value. • Unique for each different substance • Cp = symbol q = mT Cp • q - heat in joules • m - mass in grams • T – change in temperature in oC • Cp - specific heat

  30. Specific Heat: Sample Calculation How much heat will be lost when a 4.11 kg ingot of Al (aluminum) cools from 660oC to 25 oC? Given: Cp=.903 J/g oC [reference from text] m = 4.11 kg = 4110 g q = ? q = m ΔT Cp q = (4110g)(660 oC - 25 oC)(.903 J/g oC) q = 2 356 694 J q = 2 400 000 J q = 2.4 x 106 J or 2.4 x 103 Kj

  31. Law of Conservation of Energy • Animation of a closed system

  32. Law of Conservation of Energy • the total amt. of E in the universe is constant • heat is a form of energy • Therefore in a closed system... • the total amt. of heat lost by a chemical reaction should be the same as the heat gained by the surrounding area. • q lost = q gained

  33. Specific Heat: Sample Calculation Iron with a mass of 21.5g at 100.0oC is dropped into an insulated container with 132 g of water at 20.0 oC. What will be the final temperature of this system? qiron = qwater m ΔT Cp = m ΔT Cp Given: Cp = .449 J/goC [iron] Cp = 4.184 J/g oC [water] miron = 21.5 g mwater = 132 g ΔTiron = 100.0 oC-x ΔTwater = x-20.0 oC m ΔT Cp = m ΔT Cp (21.5g)(100.0 oC-x)(.449 J/g oC) = (132g)(x-20.0 oC)(4.184 J/g oC) 9.6535(100.0 oC-x) = 552.288(x-20.0 oC) 965.35 oC – 9.6535x = 552.288x – 11 045.76 oC 12 011.11 oC – 9.6535x =552.288x 12 011.11 oC =561.9415x 21.4 oC = x

  34. Temperature Scales

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