This document summarizes key concepts about the states of matter and phase changes from Chemistry Lab 1. It discusses the particle properties of solids, liquids, and gases and how phase changes require energy to either break or form intermolecular attractions. Specific heat transfer calculations are shown for melting ice and boiling water. The document also covers vapor pressure, phase equilibrium, and the decomposition and synthesis of water.

1. Chem Lab 1 Water

6. Ice- water molecules in fixed positions Water molecules free to move

8. Gas particles widely spaced Liquid particles as close as can get but free to move

12. Attractions form releasing energy

18. Liquid to Gas solid liquid enthalpy net change in enthalpy

26. Entropy There are two natural tendencies behind spontaneous processes: the tendency to achieve a lower energy state and the tendency toward a more disordered state

27. The greater the number of configurations of the microscopic particles (atoms, ions, molecules) among the energy levels in a particular state of a system, the greater the entropy of the system

31. Oxygen atom has 8 positive protons pulls harder on neg e- e- spend more time This end becomes partially negative Hydrogen atom has only one proton less pull on neg e- e- spend less time This end becomes partially positive δ + δ -

34. Electron Density in Water Molecule Notice the electron density is greater around the oxygen. The electrons are more likely to be found around the oxygen atom than the hydrogen atom

36. Dipole-dipole attractions between water molecules

37. Notice the polar covalent bonds are shorter (and thus stronger) than the dipole-dipole attractions.

39. Surface Tension in Water is the result of dipole-dipole attractions That’s why the bug can walk on top of the water. The water molecules are attracted to each other

40. Surface Tension at the particle level

41. Water drops are high and round due to the attractions between the water molecules

42. Lab 1.2 Measuring the Heat Transfer to Melt Ice

43. ICE- open crystal lattice structure

46. hot water thermometer ice Calorimeter to measure heat transfer

48. Calorimetry Calorimetry is a technique used to measure heat exchange in chemical reactions A calorimeter is the device used to make heat measurements EOS Calorimetry is based on the law of conservation of energy

49. Results 159.805 g Mass of cup with melted ice and original hot water 19.2 °C Final temperature of hot water 68.6 °C Initial temperature of hot water 99.722 g Mass of cup with hot water 3.867 g Mass of empty cup

50. Precision & Accuracy Illustrated

52. Rules for Zeros in Significant Figures Zeros between two other significant digits ARE significant e.g., 1 00 23 A zero preceding a decimal point is not significant e.g., 0.1 00 23 EOS Zeros between the decimal point and the first nonzero digit are not significant e.g., 0.001 00 23

53. Rules for Zeros in Significant Figures Zeros at the end of a number are significant if they are to the right of the decimal point e.g., 0.1 00 23 00 1 0 23. 00 EOS Zeros at the end of a number may or may not be significant if the number is written without a decimal point e.g., 1 000 . compared to 1000

54. Rules for Significant Figures in Calculations KEY POINT: A calculated quantity can be no more precise than the least precise data used in the calculation … and the reported result should reflect this fact EOS Analogy: a chain is only as strong as its weakest link

55. Significant Figures in Calculations EOS 0.762 has 3 sigfigs so the reported answer is 1.39 m 2

56. Significant Figures in Calculations Addition and Subtraction: the reported results should have the same number of decimal places as the number with the fewest decimal places EOS NOTE - Be cautious of round-off errors in multi-step problems. Wait until calculating the final answer before rounding.

62. Temperature and Phase Change Melting of Ice No change in temp Energy in to break attractions 334J/g Temp (°C) Heat transferred (J) ↑ Temp ↑ avg KE Boiling No change in temp Energy in to break attractions 2,257 J/g

63. Y

64. Entropy Changes associated with the phase changes and temperature changes

65. Lab 1.3 Liquid/Gas Phase Change

68. H 2 O (l) H 2 O (g) enthalpy BOILING WATER Products are less stable with more PE Reaction not favored based upon enthalpy ENTHALPY

69. Boiling- large bubbles form within the liquid

72. H 2 O (l) H 2 O (g) enthalpy CONDENSATION Products are more stable with less PE Reaction is favored based upon enthalpy ENTHALPY

76. Another version of Boltzmann curve.

79. Collisions of Particles cause Pressure

80. Collisions cause pressure

81. Measuring pressure with a barometer in mm Hg

82. VAPORIZATION- Molecules escape the liquid and move into the gas CONDENSATION- Molecules in the gas collide with liquid and stay in liquid

83. Only water molecules on the surface with enough KE to break dipole-dipole attractions can escape

85. Measuring Vapor Pressure Vacuum- no particles in the gas. Liquid vaporizes Proceeds to equilibrium Particles that have escaped from the liquid exert pressure to hold up the column of mercury

86. Vapor Pressure Molecules of the liquid escape the liquid and move into the gas. The molecules collide with the square. This is vapor pressure.

87. Measuring Vapor Pressure

89. Rate Time Vaporization H 2 O(l)  H 2 O(g) Rate decreases Condensation H 2 O(g)  H 2 O(l) Rate increases More particles in gas Equilibrium Rates Equal # molecules in gas stays constant

92. Vapor Pressure and Temperature At a higher temperature, more molecules escape the liquid, thus the vapor pressure is higher

96. Boiling- large bubbles form within the liquid Bubbles can only form when the vapor pressure of the liquid is equal to outside air pressure Vapor pressure within the bubble keeps the bubble from collapsing

97. In the vacuum, when air particles are removed the outside pressure decreases and water will boil at much lower temperature. The vapor pressure in the bubble will not need to increase as high to equal the outside pressure the water will boil at a lower temperature

99. Lab 1.4 Decomposition of Water

100. Decomposition of Water Electrolysis The volume ratio of hydrogen to oxygen gas is 2:1

107. Oxygen molecules O 2 Hydrogen molecules H 2 The reverse reaction- synthesis of water from hydrogen and oxygen gas

113. Just as water flows down the water falls from higher PE to lower PE, so do chemical reactions

115. Water Physical Changes Chemical Changes