1. Review for EoC Exam

2. Scientific Method While sometimes science progresses by accidental discoveries, most of the time it is by carefully planned investigations using the Scientific Method. “A logical approach to solving problem by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.”

3. Models and Theories When the data support a hypothesis, scientists usually try to explain the phenomena they are studying by constructing a model. A model in science is more than a physical object or mental picture; it is an explanation of how phenomena occur and how data or events are related. It can be visual, verbal or mathematical. If a model is very successful at explaining many phenomena, it may become part of a theory, a broad generalization that explains a body of facts or phenomena.

4. Qualitative vs. Quantitative Data Ms. Hancock has a male Irish Wolfhound mixed breed dog who is 9 years old, weighs 100 pounds, is mostly brown with a white chest and feet and some black markings, and hates riding in the car. Which data are quantitative? Which data are qualitative? Go to hyperlink →

5. Accuracy and Precision Accuracy is how close a measured value is to the actual (true) value. Precision is how close the measured values are to each other. Low Accuracy High Precision High accuracy Low precision High accuracy High precision

6. Sample Percentage Error Calculation

7. What is a significant figure? The number of significant figures or digits in a result is simply the number of figures that are known with some degree of reliability. In a MEASURED number, it is all digits up to and including the first uncertain digit. When you use a thermometer that is marked every 1 degree, your measurement will include tenths of degrees which you have estimated; so tenths are the first uncertain digit. You really can’t extend your measurement reliably to hundredths of a degree.

8. Significant Figures Significant figures indicate the precision of the measured value to anybody who looks at the data. For example, if a mass is measured as being “1100 grams”, this means that the measurement has been rounded to the nearest hundred grams. The measurement implies that the mass lies between 1050 and 1150 grams. 11001000900120013001400

9. Significant Figures If a mass is measured as being “1100.0 grams”, this means that the measurement has been rounded to the nearest tenth of a gram. The measurement implies that the mass lies between 1099.95 and 1100.05 grams. 110010991098110111021103

10. Sig Fig Rules 1.All non-zero digits are considered significant. For example, 91 has two significant figures (9 and 1), 123.45 has five significant figures (1, 2, 3, 4 and 5). 2.Zeros between non-zero digits are significant. 101.12 has five significant figures: 1, 0, 1, 1 and 2.

11. Sig Fig Rules 3.Leading zeros are not significant. 0.00052 has two significant figures: 5 and 2. 4.Trailing zeros to the right of a decimal point are significant. 12.2300 6 significant figures 0.000122300 6 significant figures 120.00 5 significant figures

12. Trailing Zeroes The significance of trailing zeros in a number not containing a decimal point can be ambiguous (unclear). For example, it may not always be clear if a number like 1300 is precise to the nearest unit (and just happens coincidentally to be an exact multiple of a hundred) or if it is only shown to the nearest hundred due to rounding or uncertainty.

13. How to be Unambiguous About Trailing Zeroes A decimal point may be placed after the number – For example "100." indicates specifically that three significant figures are meant. Using scientific notation can eliminate the trailing zero confusion. – 1300 to four significant figures is written as 1.300×10 3, while 1300 to two significant figures is written as 1.3×10 3.

14. Using Sig Figs in Calculations Your calculator can’t tell whether you’re working with measured values, which are limited in their precision, or with ‘exact’ numbers which are known precisely or math problems which are assumed to have infinite precision (their numbers aren’t measured). You get MORE digits than are justified by the measurements, and you have to make sure your answers match the degree of certainty in the original measurements.

15. Further Note When performing a calculation, do not follow these guidelines for intermediate results; keep as many digits as is practical until the end of calculation to avoid rounding errors.

16. Using Sig Figs in Calculations For addition and subtraction, the result should have as many decimal places as the measured number with the smallest number of decimal places 100.0 + 1.111 = 101.111 → 101.1 27.95 – 2.874 = 25.081 → 25.08

17. Using Sig Figs in Calculations For multiplication and division, the result should have as many significant figures as the measured number with the smallest number of significant figures. 2.02 × 2.5 = 5.05 → 5.0 0.0032 × 273 = 0.873600 → 0.87 600.0 / 5.2302 = 114.7183 → 114.7

18. States of Matter—Definition SolidDefinite volume and shape LiquidDefinite volume, indefinite shape (fits shape of container) GasIndefinite volume and shape (expands to fill the volume and shape of its container) PlasmaGas of highly ionized particles, carries electric current Bose-Einstein condensate Close to 0K, stops behaving as independent particles and clumps Neutron stars, quark-gluon plasma, etc.

19. SOM—Bonds between particles

20. Properties of Matter Properties ExtensiveIntensive Properties PhysicalChemical There are many ways to classify the properties of matter. Two of the most common are these.

21. Extensive vs. Intensive Properties ExtensiveIntensive Depend on the AMOUNT of substance Do NOT depend on the amount of substance Mass Volume Energy Boiling point Melting point Density Electrical conductivity

22. Physical vs. Chemical Properties PhysicalChemical Characteristic that can be Properties that relate to observed or measured a substance’s ability to without changing the undergo changes that the chemical nature transform it into of matterdifferent substances ColorHeat of combustion SmellpH Freezing pointReactivity to water Melting pointFlammability Boiling point Viscosity Density Specific heat

23. pH Scale from 0 (acid) to 14 (basic) Neutral is 7 pH is a measure of

24. Physical and Chemical Changes PHYSICAL CHANGES are concerned with energy and states of matter. A physical change does NOT produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle. CHEMICAL CHANGES take place on the molecular level. A chemical change produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.

25. How to Tell Chemical & Physical Changes Apart A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took place, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.

26. Density of Water

27. PHYSICAL PROPERTIES of WATER Density The density of water is easy to remember: it is 1.00 g/cm 3 or 1.00 g/mL at room temperature (25 °C). Freezing point The freezing point of water is 0°C at normal atmospheric pressure Boiling point The boiling point of water is 100 °C at normal atmospheric pressure

28. Classification of Matter SuspensionColloid Solution

29. Mixtures When two or more substances combine, and yet the substances keep their individual properties, the result is a MIXTURE. This means that NO chemical bonds have been broken.

30. Heterogeneous Mixture If the composition of the mixture is NOT the same, or uniform, throughout, this is a HETEROGENEOUS mixture. It may also be true that the composition varies from sample to sample.

31. Heterogeneous Mixtures A SUSPENSION is a heterogeneous mixture that has solid or liquid particles suspended in a liquid. These particles can be filtered or will settle out.

32. If the particles are too small to settle out, this type of mixture is called a COLLOID. Sometimes you can’t see small suspended particles unless you shine a light through the liquid. This is called the Tyndall effect.

33. Colloidal Dispersions Besides milk (solids particles in liquid), examples are smoke (solid particles in a gas), mayonnaise (liquid in liquid), fog (liquid particles in a gas), and jello (liquid particles in a solid)

34. Homogeneous Mixtures Particles far smaller than colloidal particles also may be present in a mixture. A mixture that is uniform throughout is called a homogeneous mixture. It can exist as a solid, liquid or gas (any phase). There is no Tyndall effect and you can’t see separate particles even at high magnification.

35. Solutions Solutions are composed of a SOLVENT and at least one SOLUTE. For salt water, salt is the solute and water is the solvent. SOLUTE = substance that dissolves SOLVENT = substance into which the solute dissolves SOLUTION of salt water (ocean)

36. Solutions All SOLUTIONS are homogeneous mixtures.

37. Decanting Centrifuging Evaporation Sifting or sieving Filtering Magnetic attraction Chromatography Crystallization Distillation

38. Separation Techniques Separation technique Property used for separation Examples Sifting (sieving)Particle size, density Alluvial gold sifted from finer soil and sand Visual sortingColor, shape or size Gold nuggets from crushed rock Magnetic attraction MagnetismIron can be separated from non-magnetic sulfur

39. More Separation Techniques Separation technique Property used for separation Examples DecantingDensity or solubility Liquid water poured off from settled sand; lighter oil from water FiltrationSolubility, particle size Insoluble CaCO 3 from soluble NaCl in solution

40. More Separation Techniques Separation technique Property used for separation Examples EvaporationSolubility and boiling point Soluble NaCl can be separated from water CrystallizationSolubilitySlightly soluble CuCl 2 can be separated from water

41. More Separation Techniques Separation technique Property used for separation Examples DistillationBoiling pointEthanol can be separated from water because it has a lower BP than water Centrifuge (high- speed spinning) Density, viscosityBlood constituents can be separated Chromatography (capillary action) Polarity, size, solubility Metal ions can be separated from each other due to diff’t solu.

42. Pure Substances A pure substance has a definite and constant composition (its properties are constant throughout the whole sample and its composition is homogeneous) cannot be decomposed by ordinary chemical, physical or mechanical means (sifting, filtering, crystallization, distillation, etc.) has properties that do not depend on how it is prepared or purified remains either an element or a compound (e.g., water or CO 2 ) has a sharply defined melting point and boiling point Gold remains gold even if hammered thinly.

43. Types of Chemical Reactions All chemical reactions can be placed into one of six categories. Here they are, in no particular order: 1) Combustion: A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of napthalene: C 10 H 8 + 12 O 2 ---> 10 CO 2 + 4 H 2 O 2) Synthesis: A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of: A + B ---> AB One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide: 8 Fe + S 8 ---> 8 FeS

44. Types of Chemical Reactions 3) Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form: AB ---> A + B One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas: 2 H 2 O ---> 2 H 2 + O 2

45. Types of Chemical Reactions 4) Single displacement: This is when one element trades places with another element in a compound. These reactions come in the general form of: A + BC ---> AC + B One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas: Mg + 2 H 2 O ---> Mg(OH) 2 + H 2

46. Types of Chemical Reactions 5) Double displacement: This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form: AB + CD ---> AD + CB One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate: Pb(NO 3 ) 2 + 2 KI ---> PbI 2 + 2 KNO 3

47. Types of Chemical Reactions 6) Acid-base: This is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H + ion in the acid reacts with the OH - ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water: HA + BOH ---> H 2 O + BA One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide: HBr + NaOH ---> NaBr + H 2 O

48. Basic Building Blocks of Matter An atom is the smallest unit of an element that maintains the chemical identity of that element. An element is a pure substance that cannot be broken down into simpler, stable substances and is made of only one type of atom.

49. A compound is made from the atoms of two or more elements that are chemically bonded in certain fixed proportions. (Think of the bonds as the ‘glue’ that holds the atoms of a molecule together.) The physical and chemical properties of compounds are quite distinct from those of their component elements.

50. Polarity of a water molecule Partial negative charge Partial positive charge Water also has a bent, or V-shape, as shown, rather than a linear shape like this: H – O – H with the hydrogen atoms on opposite sides of the oxygen atom.

51. Water’s polarity means that it is attracted to substances made up of electrically charged particles (like ionic compounds) and other polar molecules. This makes water a good solvent for ionic compounds. Partial negative charge Partial positive charge

52. Vocabulary ATOMIC NUMBER – the number of protons in an atom’s nucleus MASS NUMBER – the total number of protons and neutrons in an atom’s nucleus ISOTOPE – Atoms with the SAME number of protons but DIFFERENT numbers of neutrons. C-12, C-13, and C-14 are all isotopes of carbon (with 6, 7, and 8 neutrons). ATOMIC WEIGHT – the average mass of all the atoms of an element. Elements with isotopes have fractional atomic weights, depending on the percentage of each isotope that naturally occurs.

53. Isotropes vs. Allotropes Isotopes are NOT different forms of an element. For instance, carbon occurs as graphite, diamond, carbon nanotubes, and buckminsterfullerene which all have very different properties. These are ALLOTROPES of carbon, not isotopes

54. Average Atomic Masses Most elements occur naturally as a mixture of isotopes with the percentage of each isotope being nearly always the same, regardless of where on Earth the element is found. AVERAGE ATOMIC MASS is the weighted average of the atomic masses of the naturally- occurring isotopes of an element.

55. Example problem

56. The Periodic Law The Periodic Law today is known as: The physical and chemical properties of the elements are periodic functions of their atomic numbers. In other words, when the elements are arranged in order of increasing atomic number, elements with similar properties appear at regular intervals.

57. Trends in the Periodic Table Metallic character reactivity

58. Trend in Atomic Radius As you go from left to right across a period, the atomic radius (distance from nucleus to outermost electron) tends to decrease. As the positive charge in the nucleus increases, the electrostatic attraction on the electrons also increases, pulling them inward. Remember that as you go across a period, you stay at the same energy level. The atomic radius usually increases while going down a group due to the addition of a new energy level (shell)—the outermost electrons are farther from the nucleus.

59. Metallic Character Reactivity Character = how much like a metal it behaves; reactivity = how easily it loses (or gains) electrons to form chemical bonds As you go across a period from left to right, the nuclear charge increases while the number of energy levels stays the same, so there is a stronger and stronger attraction for the electrons. It becomes more and more difficult to lose electrons, so the reactivity of metals decreases as you go from left to right across the periodic table.

60. Metallic Character Reactivity As you go down a group, the nuclear charge increases but so does the number of shielding electrons. This means we have more and more energy levels and the electrons are further and further away from the nucleus, and it is easier for those electrons to come off. So going down a group means a metal’s reactivity INCREASES.

61. Ionization Energy The first ionization energy of an element is the energy needed to remove the outermost, or highest energy, electron from a neutral atom in the gas phase. The energy needed to remove one or more electrons from a neutral atom to form a positively charged ion is a physical property that influences the chemical behavior of the atom.

62. Ionization Energy Ionization energy tends to increase across a period because the greater number of protons (higher nuclear charge) attracts the orbiting electrons more strongly, thereby increasing the energy required to remove one of the electrons. Down a group, the ionization energy will likely decrease since the valence electrons are farther away from the nucleus and experience a weaker attraction to the nucleus' positive charge.

63. Electronegativity The tendency of an atom to attract pairs of electrons towards itself for bonding. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus.

64. Electronegativity Moving left to right across a period, electronegativity increases due to the stronger attraction for electrons as the nuclear charge increases. Moving down a group, electronegativity decreases due to the longer distance between the nucleus and the valence electron shell, reducing the attraction for electrons.

65. Electronegativity and Bonding The difference in electronegativity between two elements determines the type of bonding that occurs between the elements. If the difference is large, the bond will be IONIC. If the difference is small, the bond will be COVALENT.

66. Electron Affinity If ionization energy measures the tendency of a neutral atom to RESIST the loss of an electron, electron affinity measures the tendency of a neutral atom to GAIN an electron. It requires energy to remove an electron, but energy is given off when an electron is gained (except for Be, N, and noble gases which are very stable and require energy to accept another electron!). Electron affinities are generally smaller than ionization energies for reasons we’ll skip for now.

67. Electron Affinity Trends Going across the Periodic Table from left to right, electron affinities of the main group elements tend to INCREASE due, once again, to the increasing nuclear charge attracting electrons more strongly. Going down a group, electron affinities tend to DECREASE (increase bottom to top) due to the reduced attraction of electrons for the increasingly distant nucleus. The trends are the same as ionization energies.

68. Melting and Boiling Point Trends Down a Group What is the trend in BP? In MP? Why do you suppose is the cause for these trends? Going down a group, the electrostatic force holding electrons gets weaker, making bonds formed with those electrons easier to break.

69. Melting and Boiling Point Trends Across Periods 2 and 3

70. Why don’t boiling point and melting point follow a simple trend across a period? The answer lies in the type of BONDS that elements form with other elements to make chemical compounds. One of the trends you noted was an element’s METALLIC CHARACTER REACTIVITY. While we will learn about a metal’s reactivity later, now is a good time to learn about METALS, METALLOIDS and NON-METALS.

71. Metals, Metalloids, Nonmetals MetalsMetalloidsNonmetals

72. Types of Elements As you can see, the Periodic Table is broadly divided into two main types of elements, METALS and NONMETALS with a few metalloids in between. Where are metals located on the periodic table? Where are nonmetals located?

73. Properties of Metals, Non-metals, and Metalloids Metals have LUSTER (are shiny), are MALLEABLE (capable of being shaped or stretched without shattering), and conduct ELECTRICITY well. Nonmetals are usually DULL in appearance, are BRITTLE, and NONCONDUCTING. Metalloids have intermediate properties of both metals and nonmetals. Silicon and germanium are examples and are used extensively in computers.

74. What determines properties? Mostly it is the number and arrangement of the atom’s electrons. Also, metal atoms lose electrons more readily than nonmetal atoms do. Stronger attractions among the atoms of metals going from left to right in the Periodic Table means their boiling points increase.

75. Atomic Bonding Most elements do not exist in their ‘pure’ form but combine with other elements to form substances with properties different from the elements themselves. A compound is a substance that consists of two or more elements that are chemically combined in specific proportions. Compounds are formed when atoms combine with others by gaining, losing, or sharing electrons, a process called chemical bonding.

76. Types of Chemical Bonds Ionic bonds form between positive and negative ions. An ion is an atom that has an electrical charge through transferral (loss or gain) of electrons.

77. Types of Chemical Bonds Covalent bonds form when atoms share electrons. A molecule is the smallest part of a covalent compound that has the properties of that compound. Water and many atmospheric gases such as carbon dioxide are molecules with covalent bonds.

78. Types of Chemical Bonds Metallic bonds form by sharing a sea of "free" electrons among a lattice of positively charged ions.

79. Properties of Bonds Ionic compounds are rigid solids with high melting and boiling points. When solid, they are poor conductors of electricity, but when melted are good conductors. Most are Groups 1 and 2 reacting with Groups 16 and 17. Covalent compounds have low melting and boiling points and have poor electrical conductivity even when melted. Metallic compounds are malleable (easily shaped), ductile (easily drawn into wires), and are excellent electrical conductors.

80. Nuclear Fission Splitting the nucleus of an atom into two smaller nuclei is nuclear fission. The nuclear fission of heavy atoms such as uranium releases huge amounts of energy, much more (a million times!) than is released in a chemical reaction. This energy comes from converting the small amount of mass that is lost during fission into energy. (E=mc 2, you know!)

81. Fission of Uranium-235 Nuclear Fission sim

82. Nuclear Fusion Nuclear fusion is the combining or fusing of two smaller nuclei into the nucleus of a larger atom. This process occurs inside of stars and powers our sun, which burns hydrogen gas and creates helium and heavier elements. Once again, the creation of new elements results in a small mass difference, and this mass is converted into energy which the sun radiates into space and gives us heat and light.

83. Nuclear Fusion of Hydrogen

84. Why do fission and fusion produce so much energy? Nuclear fission and fusion are the splitting and combining of NUCLEI and their bonds, while chemical reactions involve the bonds of atoms’ ELECTRONS. The energy in chemical reactions comes from the difference between electrons’ bonds in reactants and in products. Energy is released as heat, when the bonds of products are stronger than in reactants. Both mass and energy are conserved in chemical reactions.

85. Why do fission and fusion produce so much energy? In nuclear reactions, energy comes from converting tiny amounts of mass lost when the bonds between protons and neutrons are broken and made. These bonds are due to the strong force. The strong force is a thousand times stronger than the electrical force which holds atoms and ions together in chemical bonds. However, the energy produced by the fission or fusion of just one atom is too small to be practical.

86. New Mexico’s Role in Nuclear Science Los Alamos Research Center, 1943 - present Founded during World War II as a secret, centralized facility for scientific research on the Manhattan Project, the project to develop the first nuclear weapons. After the Cold War, research emphasis has shifted to include medicine (vaccines for AIDS, breast cancer) and renewable energy. White Sands, Alamogordo, NM, July, 1945 First test of a nuclear weapon, ‘Trinity’ was a plutonium-implosion device (20 kilotons TNT) detonated above ground. Considered to be the start of the ‘Atomic Age.’

87. New Mexico’s Role in Nuclear Science Sandia National Labs, Kirtland AFB near Albuquerque, 1949-present Sandia Labs’ “mission [is] to maintain the reliability and surety of nuclear weapon systems, conduct research and development in arms control and nonproliferation technologies, and investigate methods for the disposal of the United States' nuclear weapons program's hazardous waste.” (Wikipedia, 4/17/13) Other research focuses on energy, the environment, critical national infrastructures, computational biology, mathematics, materials science, alternative energy, and cognitive science.

88. New Mexico’s Role in Nuclear Science Waste Isolation Pilot Plant (WIPP), near Carlsbad, 1971 - present Repository for transuranic waste including materials such as gloves, tools, rags, and assorted machinery which have come in contact with radioactive substances (mostly plutonium and uranium) in the production of nuclear fuel and weapons. Designed to store this waste in rooms in stable salt formations for 10,000 years. First waste arrived in 1999; will accept waste for another 25-35 years then be sealed.

89. New Mexico’s Role in Nuclear Science National Enrichment Facility, URENCO, Eunice, 2006-present (began enriching 2010) Plant for the enrichment of uranium for use in nuclear power plants. Natural uranium has only 0.72% U-235 (the fissionable isotope), so this plant processes it into low-enriched, reactor grade uranium (3-4% U-235). Waste Control Specialists, Andrews, TX, 2009 – present (actually 5 mi east of Eunice) Treatment, storage, & disposal company dealing in low-level radioactive, hazardous, and mixed wastes.