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Sci 1010 chapter11

Jun 27, 2015

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stanbridge

  • 1. Chapter 11

2. Chemistry a division of Physical Science Chemistry deals with the composition and structure of matter and the reactions by which substances are changed into other substances Egyptian, Chinese, and Mesopotamians wine making, worked metals, dyes, glass, pottery, embalming fluids (as early as 3500 BC Intro 3. Flourished from 500 1600 AD Main objectives (never reached): Change common metals to gold Find an elixir of life Modern Chemistry -- began in 1774, with the Frenchman Antoine Lavosier used quantitative methods and avoided mysticism, superstition, and secrecy Intro 4. Physical Chemistry applies the theories of physics Analytical Chemistry identifies what and how much is present Organic Chemistry carbon compounds Inorganic Chemistry non-carbon compounds Biochemistry chemical reactions that occur in living organisms Intro 5. Either singly or in chemical combination, the 88 naturally occurring elements comprise virtually all matter. Their chemical and physical properties affect us continually This chapter (#11) discusses the Classification of matter the Elements the Periodic Chart the Naming of Compounds Intro 6. In Chapter 5 we saw that matter can be classified by its physical phase or state solid, liquid, and gas Matter is anything that has mass Chemists use this classification, but also divide matter into several other classifications Pure Substance element or compound Mixture homogeneous or heterogeneous Section 11.1 7. Pure Substance a type of matter in which all samples have fixed composition and identical properties Element all atoms have same # of protons (gold, sulfur, oxygen) Compound two or more elements chemically combined in a definite, fixed ratio by mass (pure salt, topaz crystal, distilled water) A compound can be broken into its separate components only by chemical processes Section 11.1 8. Copyright Bobby H. Bammel. All rights reserved. Section 11.1 Faceted Topaz Al2SiO4(OH,F)2 Halite NaCl rock salt Rhodochrosite MnCo3 Lone Star Cut 9. Section 11.1 Photo Source: Copyright Bobby H. Bammel. All rights reserved. Photo Source: Standard HMCO copyright line 10. Mixture type of matter composed of varying proportions of two or more substances that are only physically mixed and not chemically combined Homogeneous (a solution) uniform throughout (coffee, alloy). Technically, it should be mixed/uniform at the atomic level. Heterogeneous non-uniform (pizza, oil/water), at least two components can be observed Formed and broken down by physical processes (dissolving, evaporation) Section 11.1 11. Section 11.1 12. Solvent the liquid or the substance in the larger quantity Solute the substance dissolved in the solvent Section 11.1 Photo Source: Standard HMCO copyright line 13. Aqueous Solution (aq) a solution in which water is the solvent When dissolved & stirred the distribution of the solute is the same throughout (homogeneous) Unsaturated Solution more solute can be dissolved in the solution at the same temp. Saturated Solution maximum amount of solute is dissolved in the solvent Section 11.1 14. A dynamic equilibrium exists between the solute dissolving and the solute crystallizing Section 11.1 15. Solubility the amount of solute that will dissolve in a specified volume or mass of solvent (at a given temperature) to produce a saturated solution If the temperature is raised the solubilities for most solids increase Section 11.1 16. Usually hotter water will dissolve more solute Section 11.1 17. When unsaturated solutions are prepared at high temperatures and then cooled, the saturation point may be reached as the solution cools However, if no crystals are present, crystallization may not take place Result Supersaturated Solution contains more than the normal maximum amount of dissolved solute at the given temperature Section 11.1 18. Section 11.1 19. The solubility of gases increases with increasing pressure Example: manufacture of soft drinks, CO2 is forced into the beverage at high pressure Once the soft drink is opened, the pressure inside the container is reduced to normal atmospheric pressure and the CO2 starts escaping The solubility of gases decreases with increasing temperature (hot soft drinks quickly lose their CO2) Section 11.1 20. In 1661 Robert Boyle proposed that the designation element be applied only to substances that could not be separated into components by any method In addition Boyle initiated the practice of carefully and completely describing experiments so that anyone might repeat and confirm them Due to this procedure (carefully documenting experiments) scientists have been able to build on previous knowledge Section 11.2 21. The earliest civilizations isolated 12 substances; gold, silver, lead, copper, tin, iron, carbon, sulfur, antimony, arsenic, bismuth, and mercury later all 12 proved to be elements Phosphorus was isolated (from urine) in 1669 P is the first element whose date of discovery is known By 1746, platinum, cobalt, and zinc had all been discovered Section 11.2 22. Around 1808 Davy, an English Chemist, used electricity from the recently invented battery to break down compounds, thereby isolating six additional elements (Na, K, Mg, Ca, Ba, Sr) By 1895 a total of 73 element were known During the next three years the noble gases He, Ne, Kr, and Xe were discovered In addition to the naturally occurring elements, 26 synthetic elements have now been created Section 11.2 23. Section 11.2 24. Human Body = 65% oxygen & 18% carbon Earths Crust = 47% oxygen & 27% silicon Analyses of electromagnetic radiation from space indicates that the universe consists of: Hydrogen 75% (simplest element) Helium 24% (second most simple element) Others 1% Earths Atmosphere = 78% nitrogen, 21% oxygen, and about 1% argon Earths Core = 85% iron & 15% nickel Section 11.3 25. Note that 74% of the mass of the Earths crust is composed of only two elements oxygen & silicon Section 11.3 26. a) The individual units (atoms) packed in a repeating pattern b) Noble gases that occur as single atoms c) Diatomic atoms (hydrogen) Section 11.3 27. Molecule an electrically neutral particle composed of two or more atoms chemically combined If the atoms are that same element, then the molecule is of an element Element examples: H2 or N2 If the atoms are different elements, then the molecule is of a compound Compound examples: H2O or NH3 Section 11.3 28. Section 11.3 29. These atoms (H, N, O, F, Cl, Br, I) are too reactive to exist as independent atoms. When writing formulas w/ these seven elements we us the diatomic form: H2 +Cl2 2HCl Section 11.3 30. Allotrope two or more forms of the same element that have different bonding structures in the same physical phase Example: Diamond and Graphite Both pure Diamond and pure Graphite are each 100% carbon (C), and are both solid But the atomic arrangement of the carbon atoms is different Section 11.3 31. Section 11.3 32. Section 11.3 33. The periodic table puts the elements in order of increasing atomic number, into seven horizontal rows, called periods The elements properties show regular trends going up or down these periods In 1869 the Russian Chemist, Mendeleev, published the original periodic table The fifteen vertical columns in the periodic table are called groups Section 11.4 34. Section 11.4 35. Representative Elements (green) Transitional Elements (blue) Inner Transition Elements (purple) Section 11.4 36. A metal is an element whose atoms tend to lose electrons during chemical reactions (+) A nonmetal is an element whose atoms tend to gain (or share) electrons (-) The metallic character of the elements increases as one goes down a group, and decreases across (always considered left to right) a period Section 11.4 37. Section 11.4 38. Section 11.4 39. Electrons are located in energy levels or shells that surround the nucleus Level 1 maximum of 2 electrons Level 2 maximum of 8 electrons Level 3 maximum of 18 electrons The chemical reactivity of the elements depends on the order of electrons in these energy levels Section 11.4 40. Section 11.4 41. The outer shell of an atom is known as the valence shell The electrons in the outer shell are called the valence electrons The valence electrons are the electrons involved in forming chemical bonds so they are extremely important Elements in a given group all have the same number of valence electrons (and similar chemical properties) Section 11.4 42. The number of electrons in an atom is the same as the elements atomic number (Z) The number of shells that contain electrons will be the same as the period number that it is in For the A group (representative) elements, the number of valence electrons is the same as the group number Lets look at Example 11.1 & Confidence Exercise 11.1 on pages 299 in your text Section 11.4 43. Section 11.4 44. Protons (Z) Electrons Section 11.4 45. The atomic size of the elements also varies periodically (refer to the Periodic Table) from 0.074 nm (H) to 0.47 nm (Cs) Atomic size increases down a group Atomic size decreases across a period The atoms on the far left are the largest due to less charge (fewer protons) in the nucleus and the outer electrons are more loosely bound Section 11.5 46. Note - the Periodic Table can be used to determine relative atomic size Section 11.5 47. Ionization energy the amount of energy that it takes to remove an electron from an atom Ionization energy increases across a period due to additional protons in the nucleus Ionization energy decreases down a group because of the additional shells situated between the nucleus and the outer electron shell. Section 11.5 48. Section 11.5 49. In order to easily and conveniently discuss chemistry we can use their chemica

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