1) Of solids, liquids, and gases, the common state of matter is the liquid state.

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1 I. Properties of LIQUIDS: 1) Of solids, liquids, and gases, the common state of matter is the liquid state. a) can exist only within a relatively narrow range of temperature and pressure. 2) The kinetic-molecular theory (KMT) can be used to explain the behavior of liquids. Assumptions of the kinetic-molecular theory of liquids include the following: a) Liquids consist of tiny (ions, atoms, or molecules). b) Liquid particles are together. c) (intermolecular or IM forces) between liquid particles are significant. d) Liquid particles are in constant, random. Particles appear to vibrate around points and are (intermolecular forces) together than gas particles e) Particles in a liquid are ordered than particles in a gas. f) The average KE of particles in the liquid state is generally than the average KE of those particles in the gas state. 3) = a measure of the amount of space occupied by a sample of matter a) Liquids have a volume (which changes only slightly with changes in temperature and pressure). Explanation using KMT: Attractive forces keep particles close together (in definite volume) 4) a) Liquids take the shape of their container (have shape). Explanation using KMT: Attractive forces keep particles close together but particles are in constant motion (they are NOT bound together in fixed positions) Particles do not move away from each other but can slide/glide past each other 1

2 5) = a substance that can flow and therefore take the shape of its container a) Liquids (and gases) are fluids. Explanation using KMT: Attractive forces keep particles together but particles are in constant motion (they are NOT bound together in fixed positions) Particles do not move away from each other but can slide/glide past each other 6) = the ratio of mass to volume for a sample of matter a) Liquids have a relatively high density compared to gases. Explanation using KMT: Liquid particles are relatively close to each other (more particles in a particular volume, amount of space) 7) = the ability of a sample of matter to have its volume reduced under pressure a) Liquids are relatively. Explanation using KMT: Liquid particles are packed close together (there is not much room/empty space to push them closer) 8) = the spontaneous mixing of two or more substances a) Liquids will diffuse through other liquids (if they will dissolve). b) Diffusion is between liquids than between gases. Explanation using KMT: Liquid particles move in constant, random motion and mix with each other Diffusion is between liquids than between gases because: liquid particles are closely packed, constantly hitting each other, and changing paths attractive forces impedes particle movement 9) = resistance of a liquid to flow Ex: cold molasses viscosity = thick; Low viscosity = a) Some liquids have a low viscosity while others have a high viscosity. 2

3 Explanation using KMT: Substances with a high viscosity typically have strong attractive forces (IM forces) between the particles and substances with a low viscosity typically have weak attractive forces (IM forces) between the particles b) Ex: Look at the picture below. o Which substance has the lowest viscosity? o Which substance has the highest? 10) = a force common to all liquids, that tends to pull adjacent parts of a liquid s surface together. o Examples: (water striders) 3. = liquid climbing the tube Water going up plant stems 4. : Attract to container (H 2 O) Attract to each other (Hg) A. A Unique Liquid WATER! 1) Water is the most liquid! 2) Water is a : a) Because of the difference in electronegativity between the strongly electronegative oxygen atom and the less electronegative hydrogen atoms, the H-O covalent bonds in the water molecule are. The water molecule is not symmetrical; so it is a! b) Electrons in each covalent bond spends more time close to the nucleus, giving oxygen a partial negative charge 3

4 c) Diagram of 5 water molecules. Notice that each water molecule can form! 3) Water is a unique substance since the solid state (ice) is less dense than the liquid state. II. CHANGING STATES OF MATTER: All matter can change (move) from one state to another It may require or, but it can be done Phase changes happen when certain points are reached o A = liquid turns into a solid o When the pressure surrounding a substance goes up, the freezing point also goes up. It s easier to freeze the substance at higher pressures. When it gets colder, most solids in size. o There are a few which expand (water) but most shrink. A. What happens to particles when energy is added or subtracted? When energy is added, particles move! When energy is taken away, particles move! Ex: Solid Liquid- a cube of ice sitting on a counter. o Energy is! o When a solid reaches the temperature of its melting point it can become a liquid. Ex: water freezes at 0 C Ex: Gas Liquid excited gas atoms need to lose some energy! o Lower the surrounding temperature. o When the temperature drops, energy will be from the gas atoms o When a gas reaches the temperature of its condensation point, it becomes a liquid. 4

5 B. Melting vs. Freezing 1. : as temp increases, the particles collide with each other more often and with a greater force so they move further apart (less intermolecular forces); the ordered arrangement of the solid state breaks down solid has melted! 2. : in the liquid state there will be a temp. (and pressure) at which average energy of the particles become low enough that attractive forces will hold the particles together (increasing the intermolecular forces) in an orderly arrangement. The particles settle into an order arrangement and form a solid. liquid freezes! Possible Changes of State: Name Change of State Example Solid Liquid Solid Gas Liquid Solid Liquid Gas Gas Liquid Gas Solid Ice water Dry ice CO 2 gas Water ice Liquid bromine bromine vapor Water vapor water Iodine vapor Solid Iodine = gas phase of a substance that is normally a SOLID or LIQUID at room temperature 5

6 C. EVAPORATION OF A LIQUID: 1) Systems: a) = everything b) = the part of the universe on which attention is focused c) = everything in the universe except the system (usually only concerned with the surroundings near the system) d) = system in which matter cannot enter and leave the system (but energy can enter and leave) Ex: Flask with stopper e) = system in which matter can enter and leave the system (also energy can enter and leave) Ex: Open beaker or flask 2) Vaporization and Evaporation. a) = a general term for the process by which a liquid changes to a gas b) = the process by which particles escape from the surface of a non-boiling liquid and enter the gas state (evaporation is a type of vaporization) 3) Use KMT to explain the evaporation of liquids: a) particles of a liquid are moving at different and have different KE b) In order for a liquid particle to evaporate (escape into the vapor/gas state) it must: be at the of the liquid posses enough KE to the attractive forces (IM forces) holding it in the liquid state c) Picture representation of evaporation: 6

7 4) Some liquids evaporate more readily than other liquids. a) = a liquid that will evaporate readily Ex: Rubbing Alcohol b) Explanation using KMT: There are relatively of attraction (IM forces) between particles in a volatile liquid (less kinetic energy is required for a particle to break attractive forces (IM forces) and escape into the vapor state). c) = a liquid that will evaporate slowly Ex: water d) Explanation using KMT: D. BOILING There are relatively of attraction (IM forces) between particles in a nonvolatile liquid (more kinetic energy is required for a particle to break attractive forces (IM forces) and escape into the vapor state). 1) = the pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature a) A vapor in equilibrium with its liquid contains gas/vapor particles that with a surface exerting pressure. 2) Different substances have different equilibrium vapor pressures at a given temperature. a) KMT Explanation: If equilibrium vapor pressure is substance readily o Substances with a high equilibrium vapor pressure (volatile) typically have (IM forces) between the particles (less kinetic energy is required for a particle to break attractive forces (IM forces) and escape into the vapor state). Ex: Rubbing alcohol If equilibrium vapor pressure is substance does evaporate readily o Substances with a low equilibrium vapor pressure (nonvolatile) typically have (IM forces) 7

8 between the particles (more kinetic energy is required for a particle to break attractive forces (IM forces) and escape into the vapor state). Ex: water 3) occurs when a liquid s equilibrium vapor pressure is equal to the external pressure on the liquid (often atmospheric pressure). 4) = temperature at which equilibrium vapor pressure EQUALS atmospheric pressure a) Different liquids boil at different temperatures o A liquid that boils at a LOW temp. and evaporates rapidly at room temp. is said to be - Ex: rubbing alcohol, gas, hairspray b) Different elevations affect boiling points: o As elevation (lower atmospheric pressure), boiling point. o Cooking time at high elevations because food does not get as. - Sea level- 100 C - Denver- 94 C - Mt. Everest - 70 C o Ex: Making a cup of tea: 8

9 E. Evaporation vs. Boiling Evaporation: Is a phenomenon Particles escape from the surface of a liquid and enter the Boiling: o At the boiling point, the is EQUAL to so bubbles form o Liquid will boil if its equilibrium vapor pressure is than the atmospheric pressure! III. EQUILIBRIUM: A. A Liquid-Vapor System at Equilibrium 1) Any (including evaporation) can be represented as follows: liquid + heat energy vapor ( process) 2) can be represented as follows: vapor liquid + heat energy ( process) 3) = a dynamic condition in which two opposing physical or chemical changes occur at equal rates in a given closed system 4) A at equilibrium can be represented as follows: liquid + heat energy vapor a) If the system is at, vaporization and condensation will occur at equal rates but there will be no net change (net amount of liquid and vapor will not change - the number of particles leaving the liquid equals the number reentering the liquid). 9

10 5) A liquid-vapor system reaching equilibrium (refer to figure below): a) Only liquid is present but particles begin to. b) Evaporation continues at the rate. There is a relatively low concentration of vapor. Vapor particles are to liquid at a lower rate than evaporation. c) Concentration of vapor has increased to the point at which the rates of and are. Equilibrium has been reached; the number of particles leaving the liquid equals the number reentering the liquid. B. Le Chatelier s Principle 1) = When a system at equilibrium is disturbed by application of a stress, it attains a equilibrium position that minimizes the stress a) A stress is usually a change in,, or. b) A system at equilibrium stays at equilibrium unless a stress is applied. c) After a stress is applied to a system at equilibrium the system cannot reestablish the original equilibrium conditions. d) After a stress is applied to a system at equilibrium the system partially counteracts the stress and, in time, establishes a new equilibrium. e) Example involving change of : In the equation: 2NO (g) + O 2(g) 2NO 2(g) o If you add more NO (g) the equilibrium shifts to the producing more NO 2(g) 10

11 o If you add more NO 2(g) the equilibrium shifts to the producing more NO (g) and O 2(g) f) 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) + energy Determine the direction of the shift resulting from each applied stress and provide reasoning: 1) Addition of NO(g) Shift = Reasoning = to consume some of the added NO 2) Removal of O 2 (g) Shift = Reasoning = to replace the O 2 (g) g) Consider a liquid-vapor system at equilibrium represented as follows: liquid + heat energy vapor If temperature increases the forward reaction is temporarily favored until a NEW equilibrium is established. Equilibrium shifts to the The new equilibrium will contain vapor particles. The new equilibrium will contain liquid particles. 11

12 IV. Phase Diagram: 1) = way of representing the state of matter (solid, liquid, gas) of a substance in a closed system as a function of temperature and pressure 2) = indicates the temperature and pressure conditions at which the solid, liquid, and gas (vapor) of a substance can coexist at equilibrium 3) = indicates the critical temperature and critical pressure 4) = the temperature above which a substance cannot exist in the liquid state no matter what pressure is applied WATER PHASE DIAGRAM 5) What is the triple point of water? 6) At what point does water boil? 12

13 Liquids & Phase Changes Review Worksheet NAME: Period: Date: 1) Describe how liquid particles are different from solid particles? 2) is the spontaneous mixing of two or more substances. 3) Arrange the following in order of increasing viscosity at room temperature: tree sap, water, salad oil. 4) What can cause a phase change of matter? 5) Describe the general volume and shape of a liquid and use KMT to explain why a liquid exhibits these qualities. 6) What is surface tension? a. What are two examples of surface tension? 7) Condensation occurs when energy is (absorbed OR released). 8) Evaporation occurs when energy is (absorbed OR released). 9) Name each of the following changes of state: a) liquid to gas d) solid to liquid b) gas to liquid e) gas to solid c) solid to gas f) liquid to solid 10) What is the difference between the intermolecular forces during melting and freezing? Explain why. 13

14 11) How are boiling and evaporation alike? 12) How are boiling and evaporation different? 13) Which would you expect to be more volatile, water or rubbing alcohol? Explain. a. Which would boil first? 14) is the pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature. 15) How does a substance evaporate, if equilibrium vapor pressure is high? a. Explain using KMT. 16) How does a substance evaporate, if equilibrium vapor pressure is low? a. Explain using KMT. 17) What is the normal boiling point of water? 18) When does boiling occur? 19) What happens to the boiling point of liquids on top of Mt. Everest? Why? 14

15 20) is a dynamic condition in which two opposing physical or chemical changes occur at equal rates in a given closed system. 21) Describe a liquid-vapor system at equilibrium. (Don t forget the particles.) 22) What is Le Chatelier s principle? a. Describe the equilibrium that exists in an inflated balloon. How does pressing on a balloon to decrease its size demonstrate Le Chatelier s principle? 23) Answer the following questions using this chemical equation: C(s) + H 2 O(g) CO(g) + H 2 (g) a. If the concentration of C was increased, the system would shift to the b. If the concentration of CO was increased, the system would shift to the 24) Use the phase diagram below to answer the following questions: a. The area on the graph that represents the gas phase is: b. The area on the graph that represents the liquid phase is: c. The area on the graph that represents the solid phase is: d. When does the triple point occur? e. What happens to a substance as you move from point A to point B? A B f. What happens to a substance as you move from point C to point A? C g. What happens to a substance as you move from point B to point C? 15

16 Unit Learning Map (6 days): Liquids & Phase Changes Mrs. Hostetter Class: Academic Chemistry B -PA Standard: Explain the relationship between the physical properties of a substance and its molecular or atomic structure. Unit Essential Question(s): How can you describe several properties of liquids using KMT (kinetic molecular theory)? Optional Instructional Tools: Guided Notes Demos: surface tension, volatile liquids Lab Materials: Cold Boil Lab Le Chat. Lab Concept Concept Concept Concept Liquids Phase changes Lesson Essential Questions: Lesson Essential Questions: Lesson Essential Questions: Lesson Essential Questions: 1) How can you describe particle spacing and motion of a liquid? 1) What can cause a phase change of matter? 2) How can you describe a liquidvapor system at equilibrium. Vocabulary: Diffusion Viscosity Surface tension Vocabulary: Melting Freezing Sublimation Deposition Vaporization Condensation Vapor Closed System Open system Evaporation Volatile Liquid Nonvolatile liquid Equilibrium Vapor pressure Boiling point Le Chatelier s Principle Phase Diagrams Triple Point Vocabulary: Vocabulary: 16

17 Liquids & Phase Changes Vocabulary: 1) Diffusion = the spontaneous mixing of two or more substances 2) Viscosity = resistance of a liquid to flow 3) Surface Tension = a force common to all liquids, that tends to pull adjacent parts of a liquid s surface together 4) Melting = as temp increases, the particles collide with each other more often and with a greater force so they move further apart (less intermolecular forces); the ordered arrangement of the solid state breaks down solid has melted! 5) Freezing = in the liquid state there will be a temp. (and pressure) at which average energy of the particles become low enough that attractive forces will hold the particles together (increasing the intermolecular forces) in an orderly arrangement. The particles settle into an order arrangement and form a solid liquid freezes! 6) Melting = Solid Liquid, Ice water 7) Sublimation = Solid Gas, Dry ice CO 2 gas 8) Freezing = Liquid Solid, Water ice 9) Vaporization = Liquid Gas, Liquid bromine bromine vapor 10) Condensation = Gas Liquid, Water vapor water 11) Deposition = Gas Solid, Iodine vapor Solid Iodine 12) Vapor = gas phase of a substance that is normally a SOLID or LIQUID at room temperature 13) Closed system = system in which matter cannot enter and leave the system (but energy can enter and leave) 14) Open system = system in which matter can enter and leave the system (also energy can enter and leave) 15) Evaporation = the process by which particles escape from the surface of a non-boiling liquid and enter the gas state 16) Volatile Liquid = a liquid that will evaporate readily 17) Nonvolatile Liquid = a liquid that will evaporate slowly 18) Equilibrium Vapor Pressure = the pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature 19) Boiling Point = temperature at which equilibrium vapor pressure EQUALS atmospheric pressure 20) Le Chatelier s Principle = When a system at equilibrium is disturbed by application of a stress, it attains a new equilibrium position that minimizes the stress 21) Phase Diagram = way of representing the state of matter (solid, liquid, gas) of a substance in a closed system as a function of temperature and pressure 22) Triple Point = indicates the temperature and pressure conditions at which the solid, liquid, and gas (vapor) of a substance can coexist at equilibrium 17