Application and Class Discussion Some meteorites found on the earth's surface are made of solid metal like iron. What kind of property intensive or extensive do you think would be most useful in identifying the metal in the meteorite? Explain. Intensive properties are unique to each substance so they are better for identifying. You can have 10 grams of just about move for answer anything or 5 mL of of just about anything, but only iron has a density of exactly 7.78 g/mL 32
11 Which of the following would be an intensive physical property? A The color of the liquid bromine is reddish brown answer B The mass of the iron pipe is 25.67 grams C The aluminum block engine has a density of 2.7 g/ mL D Both A and B E Both A and C 33
12 Tungsten is a substance with an extremely high melting point and is used in light bulb filaments. Which of the following would be an extensive property of tungsten? A Tungsten melts at 3422 C answer B Tungsten has a silver color C Tungsten has a specific heat of 0.134 J/gC D A tungsten filament is 10 cm long E A tungsten block will have a density of 15.6 g/mL 34
13 Of the following, only ________ is an extensive property. answer A density B mass C boiling point D freezing point E temperature 35
14 Which one of the following is not an intensive property? A density answer B mass C boiling point D freezing point E temperature 36
15 Which one of the following is an intensive property? answer A density B mass C boiling point D freezing point E temperature 37
Properties of Matter Summary Chemical Physical observed without changing identity of observed by changing substance identity of substance melting point, density, color, solubility, reactivity with other hardness, etc. substances Intensive Extensive independent of dependent on sample size sample size color, melting point, mass, length, density, etc. volume, etc. 38
Classification of Matter Earlier in the unit, we discussed that matter was either a pure substance or a mixture based on whether the composition was definite or variable. Matter Pure Substance Mixture definite composition variable composition 39
Mixtures Mixtures are a combination of two or more substances that can vary in composition. A classic example of a mixture would be salt water. Salt water can vary in it's "saltiness" which makes it a mixture and not a pure substance. For example, the Mediterranean sea is roughly 5% more salty around Greece than it is off the coast of Spain. Mixtures can be separated into pure substances by physical means such as heating. Desalinization factories heat salt water to evaporate the water and leave the salt behind. 40
Types of Mixtures Heterogeneous mixtures are different throughout. For instance, a raisin muffin, a chocolate chip cookie are heterogeneous. But so is sand on the beach, since you can see differences in the sand due to grain size, etc. Homogeneous mixtures are the same throughout. These are also called solutions. Tap water and the air you breathe are excellent examples of solutions. 41
Solutions Solutions are defined as homogeneous mixtures of two or more pure substances. The solvent is the substance present in the greatest abundance. All other substances are solutes . Solvent dissolves the solute. 42
Credit toTom Greebowe 43
16 A combination of sand, salt, and water is an example of a __________. answer A homogeneous mixture B heterogeneous mixture C compound D pure substance E solid 44
17 If matter is uniform throughout and cannot be separated into other substances by physical processes, but can be decomposed into other substances by chemical processes, it is called a (an) _______. answer A heterogeneous mixture B element C homogeneous mixture D compound E mixture of elements 45
18 Homogeneous mixtures are also known as __________. answer A solids B compounds C elements D substances E solutions 46
Dissociation _ _ 2+ 2+ _ _ _ _ When an ionic substance + 2 dissolves in water, the solvent pulls the individual 2+ ions from the crystal and _ _ _ 2+ solvates them. _ 2+ _ _ This process is called 2+ 2+ dissociation . _ _ _ _ 47
Electrolytes and Nonelectrolytes An electrolyte is a substances that dissociates into ions when dissolved in water. A nonelectrolyte may dissolve in water, but it does not dissociate into ions when it does so. 48
Electrolytes and Nonelectrolytes Soluble ionic compounds tend to be electrolytes. Molecular compounds tend to be nonelectrolytes, except for acids and bases. Strong Weak Nonelectrolyte electrolyte electrolyte Ionic All None None Molecular strong acids weak acids All other weak bases compounds 49
Electrolytes A strong electrolyte dissociates completely when dissolved in water. A weak electrolyte only dissociates partially when dissolved in water. No ions do not conduct Many ions electricity good conductor of electricity Few ions will conduct electricity 50
Strong Electrolytes Strong acids Strong bases HCl Group I A metal hydroxides HBr Group IIA heavy metal hydroxides HI HClO 3 HClO 4 HNO 3 H 2 SO 4 51
Strong Electrolytes Soluble ionic salts 52
19 A strong electrolyte is one that _______ completely in solution. A reacts answer B associates disappears C D ionizes(dissociates) E solidifies 53
20 A weak electrolyte exists predominantly as __________ in solution. answer A atoms B ions C molecules D electrons E an isotope 54
21 Which of the following would make the most effective electrolyte when dissolved in water? answer A CO 2 (g) B NaCl(s) C C 6 H 12 O 6 (s) D C(s) E N 2 (g) 55
22 Which of the following would make the LEAST effective electrolyte when dissolved in water? A C 2 H 5 OH(l) answer B LiBr(s) C NaNO 3 (s) D MgCl 2 (s) E All are effective electrolytes 56
Solutions The intermolecular forces between solute and solvent particles must be strong enough to compete with those between 2+ _ _ solute particles and those between solvent particles. 2+ _ _ 57
How Does a Solution Form? As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates, them. + solute + + solvent water The solute is added The negative ions are to the solvent pulled away by the positive pole of the solvent molecule The positive ions are pulled away by the negative pole of the solvent molecule 58
How Does a Solution Form? If an ionic salt is soluble in water, it is because the iondipole interactions are strong enough to overcome the lattice energy of the salt crystal. 59
23 The process of solute particles being surrounded by solvent particles is known as _____. answer A salutation B agglomeration C solvation D agglutination E dehydration 60
Energy Changes in Solution Three processes affect the energetics of solution: · separation of solute particles H1 Separation of solute molecules · separation of solvent particles · new interactions between solute and solvent. H 2 Separation of solvent molecules + H 3 Formation of solutesolvent interactions 61
Energy Changes in Solution Separated Separated solvent + solute The enthalpy change of the particles particles overall process depends on H for each of these ΔH 2 steps. Separated Solution can occur when Solvent + solute Enthalpy particles the process is endothermic ΔH 3 or exothermic. When heat ΔH 1 is released or when it is pulled in from the Solvent + Solute surroundings. Net exothermic ΔH solution process Why? Solution 62
Gibbs Free Energy Separated Separated Reactions, including solvent + solute particles particles solution, will occur spontaneously as long as the ΔH 2 change in Gibbs Free Energy Separated is negative. Solvent + solute ΔH 3 particles When the process, is ΔH 1 endothermic (heat is taken in from the surroundings), the Solution increase in enthalpy is offset ΔH solution Net by an increase in entropy. endothermic Solvent + Solute process 63
Solutions Just because a substance disappears when it comes in contact with a solvent, it doesn’t mean the substance dissolved. Dissolution is a physical change — you can get back the original solute by evaporating the solvent. If you can’t, the substance didn’t dissolve, it reacted. 64
Saturated Solutions In a saturated solution, the solvent holds as much solute as is possible at that temperature. _ _ + + _ _ Dissolved solute is in + + + dynamic equilibrium with _ + _ + _ _ + solid solute particles. + + _ 65
Unsaturated Solutions In an unsaturated solution, there is less solute dissolved in the solvent at that temperature. Solid solute is not in dynamic equilibrium with dissolved solute 66
Supersaturated Solutions In supersaturated solutions, the solvent holds more solute than is normally possible at that temperature. These solutions are unstable; crystallization can usually be stimulated by adding a “seed crystal” or scratching the side of the flask. Click here for a video on Rapid Crystallization 67
24 A saturated solution ________. answer A contains as much solvent as it can hold B contains no double bonds contains dissolved solute in equilibrium with undissolved C solute will rapidly precipitate if a seed crystal is added D E cannot be attained 68
25 An unsaturated solution is one that ______. answer A has no double bonds contains the maximum amount of solute possible, and is in B equilibrium with undissolved solute has less solute dissolved than the maximum solubility at that C temperature contains more dissolved solute than the solubility allows D E contains no solute 69
26 A solution with a concentration higher than the solubility is _____. answer A is not possible B is unsaturated C is supercritical D is saturated E is supersaturated 70
27 A supersaturated solution _________. answer A is one with more than one solute B is one that has been heated is one with more amount of solute than its solubility C must be in contact with undissolved solids D exists only in theory and cannot actually be prepared E 71
Factors Affecting Solubility Chemists use the axiom “like dissolves like." Solubity Solubility Alcohol in water in hexane CH 3 OH ∞ 0.12 methanol Polar substances CH 3 CH 2 OH tend to dissolve in ∞ ∞ ethanol polar solvents. CH 3 CH 2 CH 2 OH ∞ ∞ Nonpolar propanol substances tend to CH 3 CH 2 CH 2 CH 2 OH ∞ 0.11 dissolve in butanol nonpolar solvents. CH 3 CH 2 CH 2 CH 2 CH 2 OH ∞ 0.030 pentanol CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 OH ∞ 0.0058 hexanol solubility expressed in mol/100g solvent ∞ = completely miscible 72
Factors Affecting Solubility The more similar the intermolecular attractions, the more likely one substance is to be soluble in another. Glucose (which has hydrogen bonding) is very soluble in water, while cyclobutane (which only has dispersion forces) is not. Hydrogen bonding sites Glucose has Cyclobutanehas hydroxyl groups no polar OH groups and is highly and is essentially soluble in water insoluble in water 73
Factors Affecting Solubility Vitamin A Vitamin C soluble in nonpolar compounds soluble in water (like fats) 74
28 The phrase "like dissolves like" refers to the fact that _________. answer A gases can only dissolve other gases polar solvents dissolve polar solutes; nonpolar solvents B dissolve nonpolar solutes solvents can only dissolve solutes of similar molar mass C condensed phases can only dissolve other condensed phases D polar solvents dissolve nonpolar solutes and vice versa E 75
29 Which one of the following is most soluble in water? answer A CH 3 OH B CH 3 CH 2 CH 2 OH C CH 3 CH 2 OH D CH 3 CH 2 CH 2 CH 2 OH E CH 3 CH 2 CH 2 CH 2 CH 2 OH 76
30 Which one of the following is most soluble in hexane (C 6 H 14 )? answer A CH 3 OH B CH 3 CH 2 CH 2 OH C CH 3 CH 2 OH D CH 3 CH 2 CH 2 CH 2 OH E CH 3 CH 2 CH 2 CH 2 CH 2 OH 77
31 Which of the following substances is more likely to dissolve in CH 3 OH? answer A CCl 4 B Kr C N 2 D CH 3 CH 2 OH E H 2 78
32 Which of the following substances is more likely to dissolve in water? answer A HOCH 2 CH 2 OH B CHCl 3 C CH 3 (CH 2 ) 9 HCO D CH 3 (CH 2 ) 8 CH 2 OH E CCl 4 79
33 Which one of the following substances is more likely to dissolve in CCl 4 ? answer A CBr 4 B HBr C HCl D CH 3 CH 2 OH E NaCl 80
Temperature and Solubility A solubility chart can be used to determine the amount of solute that can be dissolved by a particular solvent at a range of temperatures. The line of a solubility chart represents a saturated solution. A point above the line represents a supersaturated solution at that temperature. 81
Temperature and Solubility A point above the line represents a supersaturated The line of a solubility chart represents a saturated solution at a specific temperature. solution. 82
34 The point on the graph represents a solution that is: answer A Unsaturated B Saturated C Supersaturated D Cannot be Determined 83
35 The point on the graph represents a solution that is: answer A Unsaturated B Saturated C Supersaturated D Cannot be Determined 84
36 The point on the graph represents a solution answer that is: A Unsaturated B Saturated C Supersaturated D Cannot be Determined 85
37 The point on the graph represents a solution that is: answer A Unsaturated B Saturated C Supersaturated D Cannot be Determined 86
38 The point on the graph represents a solution that is: A Unsaturated B Saturated C Supersaturated D Cannot be Determined answer 87
39 The point on the graph represents a solution answer that is: A Unsaturated B Saturated C Supersaturated D Cannot be Determined 88
40 The change in concentration show on the graph below is most likely due to (assume there is no phase change and the amount of water remains constant) answer More solute being added A to the solution at constant temperature B No extra solute added and the solution being cooled The solution heated, more C solute added, then the solution is cooled D None of the above 89
41 The change in concentration show on the graph below is most likely due to (assume there is no answer phase change and the amount of water remains constant) More solute being added A to the solution at constant temperature B No extra solute added and the solution being cooled The solution heated, more C solute added, then the solution is cooled None of the above D 90
42 The change in concentration shown on the graph below is most likely due to (assume there is no phase change and the amount of water remains answer constant) More solute being added A to the solution at constant temperature B No extra solute added and the solution being cooled The solution heated, more C solute added, then the solution is cooled None of the above D 91
Temperature and Solubility Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature. 92
Temperature and Solubility of gases The opposite is true of gases. Carbonated soft drinks are more “bubbly” if stored in the refrigerator. Warm lakes have less O 2 dissolved in them than cool lakes. 93
Gases in Solution The solubility of liquids and solids does not change appreciably with pressure. The solubility of a gas in a liquid is directly proportional to its pressure. In general, the solubility of gases in water increases with increasing molar mass. Larger molecules have stronger dispersion forces. 94
43 Increasing the temperature _____ the solubility of solids and ______ the solubility of gases in a liquid. answer A decreases, increases B doesn't affect, increases C increases, decreases D increases, increases E doesn't affect, doesn't affect 95
44 Increasing the pressure on a liquid _____ the solubility of solids and ______ the solubility of gases in a liquid. answer A decreases, increases B doesn't affect, increases C increases, decreases D increases, increases E doesn't affect, doesn't affect 96
45 Pressure has an appreciable effect on the solubility of __________ in liquids. answer A gases B solids C liquids salts D E solids and liquids 97
Expressing Concentrations of Solutions Recall that s olutions are homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the solvent. State of State of State of Solute Example Solution Solvent Gas Gas Gas Air Oxygen in Liquid Liquid Gas water Liquid Liquid Liquid Alcohol in water Liquid Liquid Liquid Salt in water Solid Solid Gas H 2 in Palladium Solid Solid Liquid Hg in Silver Solid Solid Solid Silver in Gold 98
Mass Percentage of solute mass of A in solution x 100% Mass % of solute A = total mass of solution 99
46 The concentration of urea in a solution prepared by dissolving 16 g of urea in 39 g of H 2 O is ______% by mass. A 29 B 41 answer C 0.29 0.41 D 0.48 E 100
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