V. Physical Behavior of Matter

Matter is classified as a pure substance or as a mixture of substances Matter is classified as a pure substance or as a mixture of substances. (3.1q) Substances Mixtures Elements Diatomic Elements Compounds J Deutsch 2003

The three phases of matter (solids, liquids, and gases) have different properties. (3.1kk) J Deutsch 2003

Properties of Solids Regular geometric pattern in the arrangement of the molecules called a crystal lattice Molecules are close together and vibrate in place Molecules do not move from place to place Solids are not compressible Definite shape and definite volume J Deutsch 2003

Properties of Liquids Molecules can move around (fluid) Molecules are farther apart than in a solid Liquids take the shape of their container Not compressible No definite shape but do have definite volume The forces of attraction between the molecules are weaker in a liquid than they are in a solid. J Deutsch 2003

The forces of attraction between the molecules are very weak. Properties of Gases Molecules fill their container (spread out) Molecules are very far apart Molecules move in straight lines until they hit something (another molecule or wall of the container) No definite shape and no definite volume The forces of attraction between the molecules are very weak. J Deutsch 2003

Regents Question: 08/02 #16 Which statement correctly describes a sample of gas confined in a sealed container? (1) It always has a definite volume, and it takes the shape of the container. (2) It takes the shape and the volume of any container in which it is confined. (3) It has a crystalline structure. (4) It consists of particles arranged in a regular geometric pattern. þ J Deutsch 2003

Regents Question: 06/02 #12 Which 5.0-milliliter sample of NH3 will take the shape of and completely fill a closed 100.0-milliliter container? (1) NH3 (s) (3) NH3 (g) (2) NH3 (l) (4)NH3 (aq) þ J Deutsch 2003

Regents Question: 06/03 #16 In which material are the particles arranged in a regular geometric pattern? (1) CO2 (g) (2) NaCl(aq) (3) H2O(l) (4) C12H22O11 (s) þ J Deutsch 2003

All substances are homogeneous. A pure substance (element or compound) has a constant composition and constant properties throughout a given sample, and from sample to sample. (3.1r) All substances are homogeneous. J Deutsch 2003

Elements are substances that are composed of atoms that have the same atomic number. Elements cannot be broken down by chemical change. (3.1u) There are more than 100 different elements Elements are represented by chemical symbols The first letter of the symbol is always a capital letter the rest are lower case J Deutsch 2003 Nitrogen Neon A temporary symbol

Some elements are diatomic Some elements are diatomic. They come in pairs when not combined with other elements. H O N Cl Br I F Diatomic Elements Hydrogen Oxygen Nitrogen Chlorine Bromine Iodine Fluorine Neon is a monatomic element Nitrogen is a diatomic element J Deutsch 2003

Compounds are substances that are composed of two or more different elements chemically combined. The elements in a compound are in fixed proportions A compound can only be decomposed by chemical means Compounds are represented by chemical formulas Compounds are electrically neutral J Deutsch 2003

Using particle diagrams to represent elements, compounds and mixtures. Diatomic element J Deutsch 2003

Regents Question: 08/02 #6 Which species represents a chemical compound? (1) N2 (3) Na (2) NH4+ (4) NaHCO3 þ Compounds are made up of more than one type of element. (Look for more than one capital letter.) Compounds are electrically neutral. J Deutsch 2003

Regents Question: 06/03 #9 Which substance can be decomposed by a chemical change? (1) Co (2) CO (3) Cr (4) Cu þ J Deutsch 2003

Mixtures are composed of two or more different substances that can be separated by physical means. J Deutsch 2003

Regents Question: 06/02 #43 þ J Deutsch 2003

Regents Question: 08/02 #51 On a field trip, Student X and Student Y collected two rock samples. Analysis revealed that both rocks contained lead and sulfur. One rock contained a certain percentage of lead and sulfur by mass, and the other rock contained a different percentage of lead and sulfur by mass. Student X stated that the rocks contained two different mixtures of lead and sulfur. Student Y stated that the rocks contained two different compounds of lead and sulfur. Their teacher stated that both students could be correct. Draw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms. J Deutsch 2003

Regents Question: 08/02 #51 Answer Draw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms. Student X Student Y Rock A Rock B J Deutsch 2003

When different substances are mixed together, a homogeneous or heterogeneous mixture is formed. (3.1s) A homogeneous mixture is called a solution A solution in which something is dissolved in water is called an aqueous solution NaCl(aq) means that sodium chloride (table salt) is dissolved in water and is therefore a homogenous mixture. (aq) stands for aqueous An alloy is a solution of metals eg. brass, bronze J Deutsch 2003

Regents Question: 06/03 #15 Which of these terms refers to matter that could be heterogeneous? (1) element (2) mixture (3) compound (4) solution þ J Deutsch 2003

Two mixtures of Hydrogen (H2) and Neon (Ne) The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties. (3.1t) Two mixtures of Hydrogen (H2) and Neon (Ne) J Deutsch 2003

Chromatography, Filtration, Dissolving, Distillation, Crystallization Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the mixture. (3.1nn) Density and polarity Particle Size solubility Boiling Point Freezing Point Chromatography, Filtration, Dissolving, Distillation, Crystallization J Deutsch 2003

Regents Question: 01/04 #12 A bottle of rubbing alcohol contains both 2-propanol and water. These liquids can be separated by the process of distillation because the 2-propanol and water (1) have combined chemically and retain their different boiling points (2) have combined chemically and have the same boiling point (3) have combined physically and retain the different boiling points (4) have combined physically and have the same boiling point þ J Deutsch 2003

Density and polarity Particle size Boiling point J Deutsch 2003

Dissolved particles are too small to be trapped by a filter A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent. (3.1oo) Dissolved particles are too small to be trapped by a filter J Deutsch 2003

Regents Question: 08/02 #7 Which mixture can be separated by using the equipment shown? (1) NaCl(aq) and SiO2(s) (2) NaCl(aq) and C6H12O6(aq) (3) CO2(aq) and NaCl(aq) (4) CO2(aq) and C6H12O6(aq) þ (aq) stands for aqueous which means dissolved in water. Dissolved particles are too small to be trapped by the filter. J Deutsch 2003

Solubility of a nonvolatile solute depends on temperature. Solubility is the maximum amount of solute that a solvent can hold at a given temperature. An unsaturated solution is one in which the solvent can dissolve more solute A saturated solution is one in which the solvent has as much solute as it can hold A supersaturated solution is one in which there is more solute dissolved than a solvent can normally hold. Make a supersaturated solution by cooling a saturated solution Supersaturated solutions are unstable and will precipitate the excess solute when a seed crystal is added. As temperature increases, solubility of a solid increases. J Deutsch 2003

Table G shows the solubilities of some gases and some solids at various temperatures when dissolved in 100 grams of water. J Deutsch 2003

A solution which is on the line is saturated A solution below the line is unsaturated A solution above the line is supersaturated J Deutsch 2003

Add a test crystal to see if a solution is unsaturated, saturated or supersaturated. Unsaturated – the test crystal dissolves Saturated – the test crystal settles to the bottom Supersaturated – a large amount of crystals precipitate from the solution J Deutsch 2003

Regents Question: 06/02 #40 According to Reference Table G, which solution is saturated at 30°C? (1) 12 grams of KClO3 in 100 grams of water (2) 12 grams of KClO3 in 200 grams of water (3) 30 grams of NaCl in 100 grams of water (4) 30 grams of NaCl in 200 grams of water þ J Deutsch 2003

The solubility of a gas depends on temperature and pressure. As temperature increases, the solubility of a gas decreases As pressure increases, the solubility of a gas increases J Deutsch 2003

Which are gases? J Deutsch 2003

Regents Question: 08/02 #48 One hundred grams of water is saturated with NH4Cl at 50°C. According to Table G, if the temperature is lowered to 10°C, what is the total amount of NH4Cl that will precipitate? (1) 5.0 g (3) 30. g (2) 17 g (4) 50. g þ J Deutsch 2003

Regents Question: 01/03 #65-66 When cola, a type of soda pop, is manufactured, CO2 (g) is dissolved in it. A capped bottle of cola contains CO2 (g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO2 (g)? A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO2 (g)? As the pressure decreases, the solubility decreases. As the temperature increases, the solubility decreases. J Deutsch 2003

Oil and water are not miscible Like dissolves like (charged solutes dissolve in charged solvents, uncharged solutes dissolve in uncharged solvents) Nonpolar solutes dissolve in nonpolar solvents Polar solutes dissolve in polar solvents Ionic solutes dissolve in polar solvents (Nonpolar) (Polar) Dry cleaners use a nonpolar solvent to get rid of oil and grease Liquids that dissolve each other are called miscible liquids. J Deutsch 2003

Regents Question: 06/03 #42 Hexane (C 6 H 14 ) and water do not form a solution. Which statement explains this phenomenon? (1) Hexane is polar and water is nonpolar. (2) Hexane is ionic and water is polar. (3) Hexane is nonpolar and water is polar. (4) Hexane is nonpolar and water is ionic. þ J Deutsch 2003

Solubility Guidelines Not all substances are soluble in water Reference Table F lists solubility rules and exceptions to those rules. J Deutsch 2003

Soluble Not Soluble J Deutsch 2003

Regents Question: 08/02 #40 Which of the following compounds is least soluble in water? (1) copper (II) chloride (2) aluminum acetate (3) iron (III) hydroxide (4) potassium sulfate þ J Deutsch 2003

Regents Question: 06/03 #14 According to Table F, which of these salts is least soluble in water? LiCl (2) RbCl (3) FeCl2 (4) PbCl2 þ J Deutsch 2003

The concentration of a solution may be expressed as molarity (M), percent by volume, percent by mass, or parts per million (ppm). (3.1pp) Molarity Percent by mass Parts per Million M = moles solute % = grams solute x 100 ppm = grams solute x 1,000,000 Liters solution Grams solution Percent by volume % = liters solute x 100 Liters solution J Deutsch 2003

Regents Question: 06/02 #42 What is the molarity of a solution that contains 0.50 mole of NaOH in 0.50 liter of solution? (1) 1.0 M (3) 0.25 M (2) 2.0 M (4) 0.50 M þ Molarity = Moles Liters J Deutsch 2003

Regents Question: 08/02 #36 How many moles of solute are contained in 200 milliliters of a 1 M solution? (1) 1 (3) 0.8 (2) 0.2 (4) 200 þ J Deutsch 2003

Regents Question: 08/02 #49 What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution? (1) 0.015 (3) 1.5 (2) 0.15 (4) 15 þ Molarity = moles liters Na 1 x 23.0 = 23.0 I 1 x 126.9 = 126.9 149.9 g / mole 0.010M = x 1.0 L X = 0.010 moles 0.010 moles x 149.9 g/mole = J Deutsch 2003

Regents Question: 01/03 #40 Solubility data for four different salts in water at 60°C are shown in the table below. Which salt is most soluble at 60°C? (1) A (2) B (3) C (4) D Salt Solubility in Water at 60 °C A - 10 grams /50 grams H2O B - 20 grams /60 grams H2O C - 30 grams /120 grams H2O D - 40 grams/80 grams H2O þ J Deutsch 2003

Hint: 200 g of water was used – table G is for 100 g of water Regents Question: 01/04 #56-58 A student uses 200 grams of water at a temperature of 60°C to prepare a saturated solution of potassium chloride, KCl. Identify the solute in this solution. According to Reference Table G, how many grams of KCl must be used to create this saturated solution? This solution is cooled to 10°C and the excess KCl precipitates (settles out). The resulting solution is saturated at 10°C. How many grams of KCl precipitated out of the original solution? KCl 90 g Hint: 200 g of water was used – table G is for 100 g of water 60 g J Deutsch 2003

The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. The greater the concentration of particles, the greater the effect. (3.1qq) Solute Moles of particles per mole of solute C6H12O6 1 (Non-electrolytes do not separate into ions) NaCl 2 (1-Na+ and 1 Cl-) CaF2 3 (1-Ca2+ and 2 F-) H2SO4 3 (2-H+ and 1 SO42-) J Deutsch 2003

Regents Question: 06/03 #23 At standard pressure when NaCl is added to water, the solution will have a (1) higher freezing point and a lower boiling point than water (2) higher freezing point and a higher boiling point than water (3) lower freezing point and a higher boiling point than water (4) lower freezing point and a lower boiling point than water þ J Deutsch 2003

Regents Question: 01/04 #13 Compared to pure water, an aqueous solution of calcium chloride has a (1) higher boiling point and higher freezing point (2) higher boiling point and lower freezing point (3) lower boiling point and higher freezing point (4) lower boiling point and lower freezing point þ J Deutsch 2003

Energy can exist in different forms, such as chemical, electrical, electromagnetic, thermal, mechanical, and nuclear. (4.1a) Kinetic energy – the energy of motion Potential energy – the energy of position (stored energy) J Deutsch 2003

The amount of thermal energy contained in the molecules depends on how fast they are moving and how many molecules there are. The total kinetic energy of all the molecules combined is called thermal energy Thermal energy is a result of the Kinetic Energy of the molecules’ motion (molecules are always moving.) Which can melt more ice: a small cup of hot water or a swimming pool of cold water? J Deutsch 2003

Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. (4.2a) The Law of the Conservation of Energy states that energy can neither be created nor destroyed. J Deutsch 2003

Heat is transferred to different materials at different rates. The specific heat capacity (C) determines the rate at which heat will be absorbed. The specific heat capacity for water is 4.18J/g The quantity of heat absorbed (Q) can be calculated by: Q=mCT m=mass T=change in temperature J Deutsch 2003

Temperature is a measurement of the average kinetic energy of the particles in a sample of material. Temperature is not a form of energy. (4.2b) Two temperature scales used in chemistry are Celsius and Absolute The unit of temperature in the Celsius scale is the degree (ºC) The unit of temperature on the Absolute scale is the Kelvin (K) J Deutsch 2003

Regents Question: 06/02 #16 Which change in the temperature of a 1-gram sample of water would cause the greatest increase in the average kinetic energy of its molecules? (1) 1°C to 10°C (3) 50°C to 60°C (2) 10°C to 1°C (4) 60°C to 50°C þ J Deutsch 2003

To convert between absolute and Celsius temperature scales use K=ºC+273 J Deutsch 2003

The concept of an ideal gas is a model to explain the behavior of gases. A real gas is most like an ideal gas when the real gas is at low pressure and high temperature. (3.4a) J Deutsch 2003

Kinetic molecular theory (KMT) for an ideal gas states that all gas particles (3.4b): 1. are in random, constant, straight-line motion. 2. are separated by great distances relative to their size; the volume of the gas particles is considered negligible. 3. have no attractive forces between them. 4. have collisions that may result in the transfer of energy between gas particles, but the total energy of the system remains constant. J Deutsch 2003

Real Gases Molecules do take up space Molecules do attract each other Energy is lost during collisions Under conditions of high temperature and low pressure, real gases behave more like ideal gases Small molecules take up little space and have weaker forces of attraction and are closer to an ideal gas Hydrogen and helium are closest to being ideal gases J Deutsch 2003

Collision theory states that a reaction is most likely to occur if reactant particles collide with the proper energy and orientation. (3.4d) Anything that will increase the number of effective collisions will increase the rate at which the reaction will occur: J Deutsch 2003

Factors that affect the rate of a chemical reaction Temperature – higher temp – faster rate Molecules collide more often and with more energy Concentration – higher conc – faster rate Molecules collide more often Increasing the pressure on a gas increases the concentration of molecules – faster rate Surface are – smaller particles – faster rate More site for the collisions to occur Catalyst – changes the mechanism to lower the activation energy J Deutsch 2003

Regents Question: 08/02 #37 Increasing the temperature increases the rate of a reaction by (1) lowering the activation energy (2) increasing the activation energy (3) lowering the frequency of effective collisions between reacting molecules (4) increasing the frequency of effective collisions between reacting molecules þ J Deutsch 2003

Kinetic molecular theory describes the relationships of pressure, volume, temperature, velocity, and frequency and force of collisions among gas molecules. (3.4c) P1V1 P2V2 T2 T2 J Deutsch 2003

Ideal Gas Laws Boyle’s Law Charles’ law Indirect Relationship between pressure and volume Temperature remains constant PxV = constant Charles’ law Direct relationship between volume and temperature Pressure remains constant V/T = constant Temperature must be Absolute temperature (Kelvins) J Deutsch 2003

Graphing the gas laws As absolute temperature increases, pressure increases at constant volume Pressure Temperature As absolute temperature increases, volume increases at constant pressure Volume Temperature As pressure increases, volume decreases at constant temperature Volume Pressure J Deutsch 2003

Regents Question: 06/02 #14 Which graph shows the pressure-temperature relationship expected for an ideal gas? þ J Deutsch 2003

Avogadro’s Hypothesis Equal volumes of different gases at the same temperature and pressure contain an equal number of particles. (3.4e) Avogadro’s Hypothesis J Deutsch 2003

Regents Question: 06/02 #15 At the same temperature and pressure, which sample contains the same number of moles of particles as 1 liter of O2 (g)? (1) 1 L Ne(g) (3) 0.5 L SO2 (g) (2) 2 L N2 (g) (4) 1 L H2O(l) þ J Deutsch 2003

The concepts of kinetic and potential energy can be used to explain physical processes that include: fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and deposition. (4.2c) Add energy (endothermic) subliming melting boiling SOLID LIQUID GAS Remove energy (exothermic) freezing depositing condensing J Deutsch 2003

Regents Question: 06/03 #17 þ Which change is exothermic? (1) freezing of water (2) melting of iron (3) vaporization of ethanol (4) sublimation of iodine þ J Deutsch 2003

A change in phase is a change in Potential Energy, not Kinetic Energy Boiling Point Potential energy changes so temperature doesn’t Melting Point J Deutsch 2003

Energy and phase changes AB - solid warms up (KE inc/PE constant) BC- solid melts (KE constant/PE inc) CD – liquid warms up (KE inc/PE constant) DE- liquid boils (KE constant/PE inc) EF – gas warms (KE inc/PE constant) J Deutsch 2003

Regents Question: 06/02 #28 As ice melts at standard pressure, its temperature remains at 0°C until it has completely melted. Its potential energy (1) decreases (2) increases (3) remains the same þ J Deutsch 2003

Regents Question: 08/02 #54 A sample of water is heated from a liquid at 40°C to a gas at 110°C. The graph of the heating curve is shown in your answer booklet. a On the heating curve diagram provided in your answer booklet, label each of the following regions: Liquid, only Gas, only Phase change Liquid Only Gas Only Phase change J Deutsch 2003

Regents Question: cont’d b For section QR of the graph, state what is happening to the water molecules as heat is added. c For section RS of the graph, state what is happening to the water molecules as heat is added. They move faster, their temperature increases. Their intermolecular bonds are breaking, their potential energy is increasing. J Deutsch 2003

Regents Question: 01/02 #47 What is the melting point of this substance? (1) 30°C (3) 90°C (2) 55°C (4) 120°C þ J Deutsch 2003

The quantity of energy absorbed or released during a phase change can be calculated using the Heat of Fusion or Heat of Vaporization Melting (fusion) or freezing (solidification) Q=mHf where Hf is the heat of fusion (for water: 333.6 J/g) Boiling (vaporization) or condensing Q=mHv where Hv is the heat of vaporization (for water: 2259 J/g) J Deutsch 2003 Hf and Hv are given to Table B – m is the mass

Fusion refers to melting. Regents Question: 08/02 #24 In which equation does the term “heat” represent heat of fusion? (1) NaCl(s) + heat  NaCl(l) (2) NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)+ heat (3) H2O(l)+ heat  H2O(g) (4) H2O(l)+ HCl(g) H3O+(aq) + Cl –(aq) + heat þ Fusion refers to melting. J Deutsch 2003

Melting Point The temperature at which a liquid and a solid are in equilibrium The melting point for ice is 0ºC The melting point of a substance is the same as its freezing point J Deutsch 2003

Regents Question: 08/02 #5 þ K=C + 273 Given the equation: H2O(s) H2O(l) At which temperature will equilibrium exist when the atmospheric pressure is 1 atm? (1) 0 K (3) 273 K (2) 100 K (4) 373 K þ K=C + 273 J Deutsch 2003

Regents Question: 08/02 #18 The solid and liquid phases of water can exist in a state of equilibrium at 1 atmosphere of pressure and a temperature of (1) 0°C (3) 273°C (2) 100°C (4) 373°C þ J Deutsch 2003

Melting point is the same as freezing point Regents Question: 06/03 #41 The freezing point of bromine is (1) 539°C (2) –539°C (3) 7°C (4) –7°C See Table S Melting point is the same as freezing point Convert K to C (K=C+273) þ J Deutsch 2003

A physical change results in the rearrangement of existing particles in a substance. A chemical change results in the formation of different substances with changed properties. (3.2a) Physical Changes Changes in phase Melting Boiling Subliming Dissolving Chemical Changes Any chemical reaction Synthesis Decomposion Single Replacment Double Replacement Combustion (burning) J Deutsch 2003

Regents Question: 06/03 #18 Which type of change must occur to form a compound? (1) chemical (2) physical (3) Nuclear (4) phase þ J Deutsch 2003

Chemical and physical changes can be exothermic or endothermic. (4.1b) Potential energy decreases Releases energy H is negative Energy is on the right 2H2 + O2 2H2O + energy Endothermic Potential energy increases Absorbs energy H is positive Energy is on the left 2H2O + energy 2H2 + O2 PE PE J Deutsch 2003

From the leg to the cold pack (Hot to Cold) Regents Question: 06/02 #64-66 A hot pack contains chemicals that can be activated to produce heat. A cold pack contains chemicals that feel cold when activated. Based on energy flow, state the type of chemical change that occurs in a hot pack. A cold pack is placed on an injured leg. Indicate the direction of the flow of energy between the leg and the cold pack. What is the Law of Conservation of Energy? Describe how the Law of Conservation of Energy applies to the chemical reaction that occurs in the hot pack. Exothermic From the leg to the cold pack (Hot to Cold) Energy cannot be created nor destroyed. It can only be changed from one form to another. The heat produced in the hot pack was stored in the chemical bonds. J Deutsch 2003

Regents Question: 08/02 #41 According to Table I, which potential energy diagram best represents the reaction that forms H2O(l) from its elements? þ J Deutsch 2003

Activation Energy (Ea) is the energy needed to get a reaction started (reach the activated complex). J Deutsch 2003

Enthalpy (H) The heat of reaction H=PE products – PE reactants The value for H is the same in the forward and the reverse reaction. Only the sign is changed. Measured in kJ (kilojoules) + H – Endothermic – Energy absorbed - H – Exothermic – Energy released The large the value of H, the more energy absorbed or released Reference Table I gives H for many reactions J Deutsch 2003

Regents Question: 08/02 #14 þ Given the reaction: CH4 (g) + 2 O2 (g)  2 H2O(g) + CO2 (g) What is the overall result when CH4 (g) burns according to this reaction? (1) Energy is absorbed and H is negative. (2) Energy is absorbed and  H is positive. (3) Energy is released and  H is negative. (4) Energy is released and  H is positive. þ J Deutsch 2003

Regents Question: 08/02 #34 According to Table I, which salt releases energy as it dissolves? (1) KNO3 (3) NH4NO3 (2) LiBr (4) NaCl þ J Deutsch 2003

Regents Question: 08/02 #50 þ Given the reaction: 2 H2 (g) + O2 (g)  2 H2O(l) + 571.6 kJ What is the approximate H for the formation of 1 mole of H2O(l)? (1) –285.8 kJ (3) –571.6 kJ (2) +285.8 kJ (4) +571.6 kJ þ J Deutsch 2003

A catalyst lowers the activation energy to speed up a reaction Activated Complex With Catalyst J Deutsch 2003

Regents Question: 06/02 #55-56 Given the reaction: A + B  C Does the diagram illustrate an exothermic or an endothermic reaction? Endothermic State one reason, in terms of energy, to support your answer. On the diagram provided in your answer booklet, draw a dashed line to indicate a potential energy curve for the reaction if a catalyst is added. The potential energy of the products is higher than the reactants, Energy is absorbed. J Deutsch 2003

The structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure. (3.1jj) Solid Liquid Gas J Deutsch 2003

Dipole-Dipole attraction between polar molecules Intermolecular forces created by the unequal distribution of charge result in varying degrees of attraction between molecules. Hydrogen bonding is an example of a strong intermolecular force. (5.2m) Dipole-Dipole attraction between polar molecules J Deutsch 2003

Hydrogen bonds occur when hydrogen is bonded to a small, highly electronegative atom. N, O and F can have hydrogen bonds when hydrogen is bonded to it. Account for the unusual properties of water: High boiling point, surface tension, six sided snowflake J Deutsch 2003

Physical properties of substances can be explained in terms of chemical bonds and intermolecular forces. Ionic bonds are strong Hydrogen bonds are strong intermolecular forces Polar molecules exhibit attraction between the + and – sides of their molecules Bonds between nonpolar molecules are weak. The more protons in the molecule, the stronger these forces. J Deutsch 2003

Regents Question: 06/02 #13 The strongest forces of attraction occur between molecules of (1) HCl (3) HBr (2) HF (4) HI þ J Deutsch 2003

These properties include conductivity, malleability, solubility, hardness, melting point, and boiling point. (5.2n) The stronger the intermolecular forces, the higher the boiling point and melting point. The stronger the intermolecular forces, the lower the vapor pressure. See Table H J Deutsch 2003

Table H – the vapor pressure of four liquids at various temperatures. As temp inc, vapor pressure inc. J Deutsch 2003

Regents Question: 06/03 #40 According to Reference Table H, what is the vapor pressure of propanone at 45°C? 22 kPa 33 kPa 70. kPa (4) 98 kPa þ J Deutsch 2003

A liquid will boil when its vapor pressure equals the atmospheric pressure. Raising the temperature will increase the vapor pressure of the liquid Lowering the atmospheric pressure will lower the boiling point On top of a high mountain, water boils at a temperature below 100C J Deutsch 2003

Standard pressure is 101.3 kilopascals (kPa) or 1 atmoshpere (atm) The normal boiling point occurs when the atmospheric pressure is 101.3 kPa (standard pressure) The normal boiling point of ethanol is 80ºC. J Deutsch 2003

Regents Question: 08/02 #28 As the pressure on the surface of a liquid decreases, the temperature at which the liquid will boil (1) decreases (2) increases (3) remains the same þ J Deutsch 2003

Regents Question: 08/02 #30 As the temperature of a liquid increases, its vapor pressure (1) decreases (2) increases (3) remains the same þ J Deutsch 2003

Regents Question: 08/02 #44 The vapor pressure of a liquid is 0.92 atm at 60°C. The normal boiling point of the liquid could be (1) 35°C (3) 55°C (2) 45°C (4) 65°C þ The normal boiling point is the temperature at which a liquid boils when the atmospheric pressure is standard pressure (1 atm or 101.3 kPa) J Deutsch 2003

Regents Question: 01/03 #68 What is the vapor pressure of liquid A at 70°C? Your answer must include correct units. 700 mm Hg J Deutsch 2003

Regents Question: 01/03 #69 At what temperature does liquid B have the same vapor pressure as liquid A at 70°C? Your answer must include correct units. 113°C J Deutsch 2003

Regents Question: 01/03 #70 Which liquid will evaporate more rapidly? Explain your answer in terms of intermolecular forces. Liquid A will evaporate more rapidly because, at any temperature, it has the higher vapor pressure. J Deutsch 2003