F’orm WS6. 3. IA Name PHASES OF’ MATTER Date Period a Heating a substance in a given phase generally causes the temperature to increase. This causes the particles to move faster and collide harder. Harder, faster collisions cause particles to rebound harder moving them further apart. Larger distances between particles weakens the forces of attraction between them. When the forces of attraction are weak enough, the distance between the particles increases markedly and the phase changes. As a result, a solid melts and a liquid evaporates. The reverse happens when a substance cools. As the particles slow down and the collisions weaken, the particles move closer together increasing the forces of attraction between the particles. As a result, a gas condenses and a liquid freezes. At normal atmospheric pressures, some substances change directly from a solid to a gas. This change is called sublimation. This is what occurs when ice cubes shrink in the freezer, or when a wash dries on a clothesline on a cold winter day. Some substances, such as (s)j, never pass through a liquid phase at standard pressure 2 dry ice [C0 [101.3 kPaJ. A gas can also change directly to a solid. This is called deposition. Answer the questions below based on your reading and on your knowledge of chemistry. 1. In the space below are the labels solid, liquid, and gas. Draw arrows between them to represent phase changes. Label each arrow with the name of the phase change it represents. Two examples are done for you. Also, draw an arrow labeled temperature to show the direction in which temperature is increasing. Solid Liquid as Melting 2. I. Under what conditions does a solid melt 9 Why? fL 3. Under what conditions does gas conden i iib 1 d-cj /‘/e 1J ? Why? Ui’k ,f (Continued I’) e y (fpe4 ) >J ‘// t / 3 Cf Form WS6, 3. 1A nLt,rf: Phase Changes PHASES OF MATTER 4. Page 2 Why do substances change phase as the temperature changes? Refer to the distance between particles and the force of f Le_ attraction between them in your answer. L / aJ 5. eh% fh., pci’ k o it f/r(/,Vt ,ti, _, .. •,— — To the right is a graph showing the relationship between temperature, pressure, and phase for a substance. Answer the questions below based on the graph. a. Draw a dotted line going across the graph at a pressure where sublimation 0 could occur. Label it “a.” b. Draw a solid line going across the graph at a pressure where melting and vaporization could occur. Label it “b.” c. Under normal conditions, carbon dioxide gas turns directly into a solid as it is cooled. What could be done to make carbon dioxide form a liquid? (kj Liquid - tJ I 6. Under normal conditions, butane is a gas. In butane lighters, the gas is put under pressure and it forms a liquid. Explain why a gas liquefies under pressure even with Ut cooling it. Ottir ) — / o 7. r//io’ What would happen to a liquid at a constant temperature as the pressure is reduced? Why? b : 0 I i 1rvL jj’ N / P ’ 3 -k t 1ff / ‘C 8. © Evan P. Silberstein, 2003 ) nii’f: Form WS6,3.313 Name PHASES OF MATTER Date Period Vajr rrsur’ An open glass of water left standing around will eventually evaporate even with out being heated. When water evaporates, it changes from a liquid to a gas called water vapor. Water vapor takes up more space than an equal mass of liquid water. As a result, in a closed container, the vapor that forms can exert a significant amount of pressure. This pressure is known as vapor pressure. Even in an open container, the vapor is confined by the air pressing down on it. Some of it collects at the surface and exerts pressure, Occasional high energy molecules at the water’s surface escape. That is why the water eventually evaporates. But for a water to expand arid form vapor bubbles throughout the liquid as it does when it boils, the vapor has to exert as much pressure as the blanket of air confining it. As a liquid is heated, more of it turns into vapor, and the vapor pressure increases. When the vapor pressure reaches atmospheric pressure, the liquid boils. Under greater external pressure, the liquid boils at a higher temperature. Let me ou The graph below shows the vapor pressures of four common liquids as a function of temperature. Refer to the graph to answer the questions that follow. 1. Which ofthe substances above has the lowest boiling point? 2. Which ofthe substances above has boilingpointof l0O°C9 Vapor Pressur of Four Uqulds Il 7)14 I 1.? ‘4 (O €4 On — e 3. 4. Which ofthe substances above has the highest boiling point? Which ofthe substances above has the highest vapor pressure at 40°C? 5. Which of the substances above will boil at 79°C? . 6 6Z . 7 ri’. I - ‘ ,, I 4fVI : :: : :: 7 e - I lid I - i: ¶1 4- I 2’ 1 at d - } 6 I I [€4 - At what temperature will alcohol boil when the atmospheric pressure is 50 kPa? At what atmospheric pressure will propanone boil at 20°C? : 25 50 15 100 mmo.rtu. •c €4 f At what atmospheric pressure will water boil at 90°C? Which of the substances above has the lowest vapor pressure at 70°C? 10. As the pressure decreases, the boiling point of water (a) increases, (b) decreases, (c) remains the same. What is the vapor pressure of water at 60°C? © Evan P. Silberstein, 2003 125 irvq: Form WS6.3.2A Name PHASES OF MATTER Date Period Curv As a substance is heated, its particles begin to move faster and spread apart. The speed of the particles is related to their kinetic energy. The relative position of the particles is related to their potential energy. As solids, liquids, and gases are heated, most of the energy that is absorbed is converted to kinetic energy, and the temperature goes up. But as a substance melts or vaporizes, its particles spread out tremendously. As a result, the energy absorbed produces changes in the potential energy of the particles, so the temperature does not change as the phase changes. For that reason, the freezing point and the melting point of a substance are the same. Base your answers to the following questions on the graph below which shows 10.0 kg of a substance that is solid at 0°C and is heated at a constant rate of 60 kilojoules per minute. What is the temperature at which the substance can be both in the solid and the liquid phase? 2. L—J. 3. 5W K During which lettered intervals is the internal potential energy of the substance increasing? During which lettered intervals is the kinetic energy of the particles increasing? How much heat is added to the substance from the time it stops melting to the time that it begins to boil? 0°C ‘4- B 2 0°C 14U 0 I : EZEEEE7EEZEEE 80 6O———— 0 4 - 8 . 12 Time 16 20 in minutes , )(; What is the total heat needed to melt the substance (starting at time 0)? /t/f °1(T 6. = 2 What is the total heat needed to vaporize the substance (starting at time 0)? / 1 ‘/ 0 7. What is the heat of vaporization of the substance? 8. During which lettered intervals is the substance solid? 9. During which lettered intervals is the substance in the liquid phase? 10. During which lettered intervals is the substance in the vapor phase? 1iOt ii. What is the temperature at which the substance can be both in the liquid and the vapor phase? © Evan P. Silberstein, 2003 24 ?tr(: Form WS8 . 1.. 3A Name SOLUTtONS Date ii Period @li ai Gas A factory releases clean, warm water into a stream. The stream becomes severely polluted as a result. How does this happen? Fish living in the water depend on dissolved oxygen in order to breathe. Like other gases, oxygen molecules tend to spread out. In order to dissolve them, it is necessary to confine them. Heat speeds the molecules up and makes them spread out more—exactly the opposite of what is needed to dissolve them. As a result, heat drives the oxygen out of the water, causing the fish to die. The dead fish begin to decay. Growing decay bacteria deplete the water of oxygen even further. In this way, clean warm water can pollute a stream. The process of dissolving gases is opposite to the process of dissolving solids because of the differences between gases and solids. ,.. P•. - Answer the questions below based on your reading above and on your knowledge of chemistry. 1. A warm can of soda is dropped and bounces down a flight of stairs. When it is opened, carbon dioxide gas coming out of solution causes it to spray all over. Explain the affect of each of the following: a. 1 The fact that the soda was warm. 7 /%..J,:)j b. The fact that the soda was dropped and bounced down a flight of stairs. Y P 1 7’I — (O c. The fact that the can was opened. fr IF (o F 2. When a gas dissolves, the particles need to be confined. Vhat do the particles of a solid need to do in order to dissolve? Nt J h fPri.J 3. Sugar is added to a hot cup of coffee and stirred. The sugar dissolves. Explain the affect of each of the following: L a. The factat the coffee was hot. b. The fact that the coffee was stirred. K Continue i’ t c ,,/ iu.3t,r(: Form WS8.1.3A Dissolving Solids and Gases SOLUTIONS 4. Page 2 Which dissolves faster, a teaspoon of sugar or a sur cube? Why? WOIrtj7J frC 1/YJ ffrJ I 5. A solid is added to water and stirred. Some of it dissolves, but not all. What happens to the rate at which the solid is dissolving between when it was first added and when it stopped dissolving? Explain. (HINr. Equilibrium!) Vcjt (fJ j (‘/,r4 h*J 6. The table below lists four factors that may effect the rate at which solids and gases dissolve. Fill in the table by indicating if the rate of dissolving increases, decreases, or is not effected. Then explain why. Affect on Rate of Solution for: Factor Solid Solutes Gaseous Solutes Crushing L Stirring Increasing the amount of dissolved soMe Increasing Temperature / © Evan P. Silberstein, 2003 _______________________________________ _______________ _____ ____________ ____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _ _ _ _ _____ _____ _____ _____ _____ _____ _____ _____ _ _____ _ (?rL3rf Porm WS8 1. 2A . Name SOLUTIONS Date Period iutlicJ Cuvv The solubility of solid solutes generally increases as temperature increases, while the solubility of gaseous solutes generally decreases as temperature increas es. A solution that holds as much solute as can dissolve at a given temperature is saturated. A solution that can dissolve more solute at a given temperature is unsaturated. A solution that holds more solute than can dissolve at a given temperature is supersaturated. The amount of solute that is needed to form a saturated solution at various temperatures can be graphed. This is what is shown in Table G. The values in Table G are based on solute dissolved in 100 of water. g Since water has a density of 1 g/mL, the graph can be considered to be based on 100 mL of water. A 200 niL sample of water would be able to dissolve twice as much at each temperature. 1bt. G Solublilty Curve 140 130 / - 1 KN0 120 110 .3 Suporsted• \ / S Unsaturated— Answer the questions below by referring to Table G. I 1. The compound which is the most soluble at 20°C is 2. The compound which is the least soluble at 10°C is 4° 30 24 - - 3. The compound which is the least soluble at 80°C is 4. The number of grams of potassium nitrate needed to saturate 100 mL of water I at7O°Cis I ‘ )‘) 0102030405060103090100 Thmp.rw. (CC) c 1 5. The formulas of the compounds which vary inversely with the temperature are 7 co- and 1v1-i HdI 6. One hundred mL of a sodium nitrate solution is saturated at 10°C. How many additional grams are needed to saturate the solution at 50°C? Sc 7. One hundred mL of a saturate KCI solution at 80°C will precipitate 10 grams of salt when cooled to what temperature? t4 8. The o salts that have the same degree of solubili at 70°C are < 3 and \/c /eb, 9. The salt with a solubility is least affected by a change in temperature is 10. The salt that has the greatest increase in solubility in the temperature range between 30°C and 50°C is 11. The number of grams of sodium nitrate that must be added to 50 mL of water to produce a saturated solution at 50°C is 12. A saturated solution of potassium chlorate is made at 10°C by dissolv ing the correct mass of salt in 100 mL of water. /1— When the solution is heated to 90°C, how many grams must be added to saturate the solution? Continue _____ _____ _____ Lbrf: Form W58, 1 .2A Solubility Curves SOLUTIONS Page 2 13. At what temperature do saturated solutions of sodium chloride and potassium chloride contain the same mass of solute O 6 per 100 mL of water? 7) 14. A saturated solution of potassium nitrate is prepared at 60°C using 200 mL of water. Lf the solution is cooled to 30°C, how many grams will precipitate out of the solution? I ‘- 5 //I 15. How many more grams of ammonia can be dissolved in 100 mL of water at 10°C than at 90°C? 16. A saturated solution of sodium nitrate in 100 mL of water at 40°C is heated to 50°C. The rate of increase in solubility 05/tO 1 grams per degree is / /“ 17. Thirty grams of KCI is dissolved in 100 mL of water at 45°C. The numbe r of additional needed to make the solution saturated at 80°C is 2o © Evan P. Silberstein, 2003 grams of KCI that would be ___________ ______ fli3t,rrf: Form WS8. 2. IA Name SOLUTIONS Date Period Fijit C’cat,i@ The directions on a can of condensed soup say to mix the can of soup with one can of water. What would happen to the flavor if it were mixed with two or three cans of water instead? When two substances are mixed, the amount of one compared to the amount of the other is known as the concentration, Adding extra water makes the concentration of the soup lower than what is called for in the recipe—and it tastes it! There are several ways of measuring concentration—mass per unit volume, percentage by mass, percentage by volume, and parts per million (ppm). See the examples below: Concentration ppm Mass of solute( g) Volume of Solvent or Solution(mL) percent mass = = 25g 100. ml = . / , mass sotute; mass (solution) mass(solute) x 1,000,000ppm inass( solution) Sample Problem About 0.0047 g of ammonia are dissolved in 20.0 g of water. Express this in parts per million. Sample Problem What is the concentration of a solution prepared by dissolving 25 g of KNO 3 in 100. mL of water? Concentration = Step 1: Find the mass of the solution 20.0 g + 0.0047 g = 20.0047 g Step 2: Divide the mass of the solute by the mass of the solution and multiply by 1,000,000 ppm. 0.0047g ppm 1,000,000ppm = 235ppm 20.0047g 0.25k percent volume 100% Sample Problem What is the percent by mass of a solution containing 12.3 g of caffeine dissolved in 100.0 g of water? Step 1: Find the mass of the solution 100.0 g + 12.3 g 112.3 g = volume (solute) x 100% vo’ume j5OtUtIOfl) Sample Problem What is the percent by volume of a solution containing 18.2 mL of glycerine (CH ) dissolved in 85.0 mL of 3 O 6 water? Step 1: Find the volume of the solution. 18.2 mL + 85.0 mL = 103.2 mL Step 2: Divide the mass of the lute by the mass of the solution and multiply by 100 % I 2.3g percent mass— x 100% = 11.0% I 12.3g Step 2: Divide the volume of the solute by the volume of the solution and multiply by 100% 182mL percent volume = x 100% = 17.6% I 03.2mL Continue ir tr: Form WSB.2. IA Finding Concentration SOLUTIONS Page 2 Answer the questions below based on the sample problems. 1. What is the concentration of 45 mL of a solution containing 9.0 g of KCIO ? 3 61 C/ 6. If 19 mL of alcohol are dissolved in 31 mL of water, what is the percentage by volume of alcohol? 11L /_ / _ 2. A solution is prepared by mixing 20.0 g of NaNO 3 with 100. mL of water. What is the percentage mass of the solution? (Assume density of water is I /mL) $) I i air? 3’ /()1o/ jj 7. If 0.002 g of PbCI 2 are dissolved in 2.0 L of water, how many parts per million are dissolved? (Assume density of water is I 3 3. A 250. mL sample of air at STP contains approximately 52.5 mL of 0 (g). What is the percentage of oxygen in 2 7 2S u o k( 8. If 15 g of KNO 3 are dissolved in 235 g of water, what is the percentage of solute by mass? i 5J Kt’]c2 IIu7OL 4. A polar solvent is prepared by mixing 27.5 mL of propanone with 222.5 mL of water. What is the percentage by volume of propanone in the mixture? / r 9. What is the percentage by mass of a solution prepared with 34 g of KI and 126 g of water? - 5. How many parts per million of sulfur dioxide are there in a solution containing 0.065 g of sulfur dioxide in 5,000 mL of water? (Assume density of water is I ‘mL) / q ç 10. What is the concentration of a solution made with 0.056 g of CO,(g) and 200 mL of water? ooc6cOL ) kt © Evan P. Silberstein, 2003 ,L. Form WS8.2.2A Name SQL UT I ON S Date Period larL( One of the most useful measures of concentration in chemistry is molari ty (M). Molarity is the number of moles of solute per liter of solution. A two molar (2 M) solution contain s two moles of solute per liter of solution. moles(solute) M L(solution) Recall that the number of moles is determined by dividing the number ofgrams by the gram formula mass (GFM). There are a number of formulas for calculation that come from these relationships: g GFMx L • moles = MxL • g = M x GEM x L A two molar solution Below are some sample problems that show how to apply these formulas. Sample Problem I Find the molarity of 100. mL of a solution that contains 0.25 moles of dissolved solute. Sample Problem 2 Find the molarity of 500. mL of a solution that contains 4.9 g of dissolved sulfuric acid (H SOj. 2 Step 1: Convert all volumes to liters 0.OOIL = 0.IOOL lmL Step 1: Find the GFM x 7 H =1 xl S =32 x4 0 =16 = 7 32 = 64 98 Step 2: Convert all volumes to liters 00O1L 500.mL = 0.500L lmL Step 3: Substitute values into the correct equation = g 49g GFW x L 01 (98 Xo.5oo L) Step 2: Substitute values into the definitional equation = mot = 0.25mo1 = 2iM L O.IOOL 4.- = Sample Problem 3 How many moles of solute are dissolved in 250. mL of a 3.0 M solution? Sample Problem 4 How many grams of sodium 3 carbonO C 2 ) ate(Na are needed to prepare 250 mL of a 0.10 NI solution? Step 1: Convert all volumes to liters 0.OO1L 2SftmLx =0250L I ,nL Step 2: Substitute values into the correct equation mo! = 11 x L = (30”X025OL) 0.75mo1 Step 1: Find the GFM Na = 23 C =12 0 =16 -4 2 x x 3 = 46 =12 =48 106 Step 2: Convert all volumes to liters 0.00 IL 250.mL x = 0.250L lmL Step 3: Substitute values into the correct equation g = A-f x L x GFM = (0.10”yrX1O6,,,)(0.250L) = 2.7g .rjf,rf: Eorm WS8 .2. Molarity SOL(JT IONS Page 2 Answer the questions below based on the reading and the sample problems on the previous page. I. Determine the molarity of 500. mL of a solution with 0.35 mol of dissolved so 6. What is the molarity of 300 mL of a solution that contains 0.60 mol of dissolved ammonia? O. 2. A 200. tnL samp’e of a solution contains 4.0 g ofNaOH. What is its molarity? x 3DOL- 7. What is the molarity of 5.0 L of a solution containing 200. g of dissolved CaCO ? 1 I /i\4’1 3. How many grams of KNO 1 are needed to prepare 25 mL of a 2.0 M solution? 4. How many moles of MgSO 4 are contained in 50. mL of a 3.0 M solution? 5. How many grams of CaCI 2 a 0.75 M solution? 8. How many grams of NaCI are needed to prepare 500. mL of a 0.400 M solution? 9’ 5?CL. ).M yt O U7SL 3,D,.JMdO I2O3 Oto5oLx 7 L. 4) It O 2 Oj 9. How many moles of solute are contained in 3.0 L of a 1 .5 M solution? 9, OL // 10. What is the molarity of 750 mL of a solution that contains 40.0 g of dissolved CuSO ? 3 O,t0L x © Evan P. Silberstein, 2003 (3?’) 3 rf: Form WS8.3.IA N a me SOLUT IONS Date OaiS iaW Pc r i od rie8 After a winter storm, people spread salt on the walks to help melt the ice. Salt reduces the freezing point of water, Actually, any soluble solute Thes are reduces the freezing point of water by interfering with crystallization. salty and In coldi this way, antifreeze keeps the water from freezing in an automobile radiator. This phenomenon is called freezing point depression. Antifre eze is left in the radiator during the summer. It also prevents the radiator from boiling over by raising the boiling point. Dissolved solute reduces the vapor pressure, raising the boiling point. This is called boiling point elevation. The amount the freezing point > Vapor pressure ezaited by water • Vapor oressure ex.ited by sdut is depressed or the boiling point is raised depends on the concentration of dissolved Dad misinterprets freezing point depression. solute. The higher the concentration of dissolved solute is, the greater the effect on the boiling point or the freezing point is. Only the concentration of the particles of dissolved solute is important. The nature of the solute is not. A mole of dissoLved sugar has exactly the same effect on the freezing point and boiling point of 1,000 g of water as a mole of antifre eze because it contains the same number of particles. Ionic compounds dissoc iate producing more particles per mole. One mole of dissolved sodium chloride, for example, produces one mole of aqueous sodium ions and one mole of aqueous chloride ions for a total of two moles [NaCl(s) —f Na(aq) + Cl(aq)J. One mole of dissolved sodium chloride, therefore, has twice the effect on the boiling and freezin g points of 1,000 g of water as one mole of dissolved sugar. It is not the nature of the solute that matters, but only the concentration of dissolved particles that determines how large the change in freezing point or boiling point will be. Properties of a solutio n, such as this, which are dependent only on the number of particles in solution, and not on their nature are called colligative properties. Answer the questions below based on your reading and on your knowledge of chemistry. 1. Why ai boiling pot elevation and freezing point depression consid ered colligative properties? 9oJ1 --—; I c,’-, 2. Why is salt put on icy roads and sidewalks in e winter? c) /oi’i • I i I’ezj 3. I-low will the boiling points of pure water and sea water compare? Why? Continue V’ IV cJ Ji I e _ _ _ _ _____ _ _____ ___ F. itrç: E’o rrn WS 8 3 LA . Understanding Colligative Properties . SOLUTIONS Page 2 Solve the following boiling point elevation problems and the freezing point depression problems as shown in the sample problems below. [NOTE: At standard pressure, I mol of dissolved particles will elevate the boiling point of 1,000 g of water by 0.52°C and will depress the freezing point of 1,000 g of water by 1.86°C1 Sample Problem Find the boiling point of a solution containing 1,000 g of water and 2 mol of dissolved NIgF,. Sample Problem Find the freezing point of a solution containing 1,000 g of water and 30 g of dissolved antifreeze 4 11 (C ) 2 0 . Step 1: Determine the number of moles of solute particles 2MgF,(s) —‘ 2Mg (aq) i- 4F(aq) mol =6 2 Step 1: Determine the number of moles of solute particles 12x2 C 24 g = 30g mol = — 0.Smol I-I i’t— ‘ GFM 60’, 0 = l6x2= 60 Step 2: Multiply the freezing point depression per mole by the number of moles of solute to find the freezing point depression FPD = I .86dIrnol x 0.5 mol 0.93°C Step 3: Subtract the freezing point depression from 0°C FP = 0°C —0.93°C =—0.93°C — Step 2: Multiply the boiling point elevation per mole by the number of moles of solute to find the boiling point elevation BPE 0,52/molx 3 mol°3.l2°C Step 3: Add the boiling point elevation to 100°C BP= l00°C+3.12°C= 103.12°C A 4. One mole of dissolved particles elevates the boiling point of 1,000 g of water by 0.52°C. At standard pressure, what will the boiling point of a solution be if it contains 1,000 g of water and: a. I mol of antifreeze 2 (C 0 4 H ,)? b. I mol of salt (NaCI)? c. I mol of ethanol 2 (C O 5 H H)? d. 2 mol of glycerol 3 (C ) 0 6 K ? e. 2 mol of CaCI,(aq)? 4 3. . f. 5 mol of sucrose 1 O 2 H 2 (C, ) ? 2 g. I mol of KNO (aq)? 3 h. 3 mol of 3 Ba(N ( 2 ) aq)? 0 i. 40 g of NaOH(aq)? j. 270 g of glucose 6 (C ) O 2 H ? 4 s/,.../ /, 0 Y , C / 5. One mole of dissolved particles depresses the freezing point of 1,000 g of water by 1.86°C. At standard pressure, what will the freezing point of a solution be if it contains 1,000 g of water and: a. 1 mol of glucose O 12 (C1) 6 ? 1 b. I mol of BaCl(aq)? c. 2 mol of methanol 3 (CH O H)? d. 3 mol of glycerol 3 (C 0 6 H j? e. 2 mol of 4 CuS ( aq)? O I fri b 0 3 12 S .T t f. 4 mol of sucrose O 2 H 12 (C ) 1 ? , g. 3 mol of KNO (aq)? 3 h. 2 mol of salt (NaC1)? i. 150 j. of KHCO (aq)? 3 ØOJZL-. I, 7a-..i 180 g of glucose (C )? O 2 H 6 I, © Evan P. Silberstein, 2003 2 ‘ /I b:6i