1) Of solids, liquids, and gases, the least common state of matter is the liquid state. a) Liquids 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 kineticmolecular theory of liquids include the following:
a) Liquids consist of tiny particles (ions, atoms, or molecules). b) Liquid particles are close together. c) Attractive forces (intermolecular or IM forces) between liquid particles are significant.
d) Liquid particles are in constant, random motion. e) Particles appear to vibrate around moving points and are closer (intermolecular forces) together than gas particles Particles in a liquid are more ordered than particles in a gas. f) The average KE of particles in the liquid state is generally lower than the average KE of those particles in the gas state.
3) Volume = a measure of the amount of space occupied by a sample of matter a) Liquids have a definite volume (which changes only slightly with changes in temperature and pressure). Explanation using KMT: Attractive forces keep particles close together (in definite volume)
4) Shape a) Liquids take the shape of their container (have no definite 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
5) Fluid = 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) Density = 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) Compressibility = the ability of a sample of matter to have its volume reduced under pressure a) Liquids are relatively incompressible. Explanation using KMT: Liquid particles are packed close together (there is not much room/empty space to push them closer)
8) Diffusion = the spontaneous mixing of two or more substances a) Liquids will diffuse through other liquids (if they will dissolve).
b) Diffusion is slower between liquids than between gases. Explanation using KMT: Gas particles move in constant, random motion and mix with each other while liquid particles are closely packed (attractive forces impede particle movement), constantly hitting each other, and changing paths.
9) Viscosity = resistance of a liquid to flow Ex: cold molasses High viscosity = thick; Low viscosity = runny Some liquids have a low viscosity while others have a high viscosity. 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
Ex: Look at the picture below. Which substance has the lowest viscosity? Which substance has the highest? A B C D E E A
10) Surface Tension= The energy required to increase the surface area of a liquid by a given amount; results from an uneven distribution of attractive forces.
It is a measure of the inward pull by particles in the interior. The stronger the attraction between particles, the greater the surface tension
1) Droplets 2) Objects float (water striders)
3) Capillary action = liquids ability to flow up thin tubes; going against gravity Ex: Water going up plant stems
4) Meniscus: Attract to container (H 2 O) Attract to each other (Hg)
1) Water is the most abundant liquid! 2) Water is a polar molecule: 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 highly polar. The water molecule has an unequal distribution of charge; so it is a polar molecule!
b) Electrons in each covalent bond spends more time close to the oxygen nucleus, giving oxygen a partial negative charge
c) Diagram of 5 water molecules. Notice that each water molecule can form 4 hydrogen bonds!
3) Water is a unique substance since the solid state (ice) is less dense than the liquid state. a) Because of the hydrogen bonding, the arrangement of the molecules in the solid crystalline structure take up more space, yet have the same mass; making ice less dense than liquid water.
Phase change = transitioning from one state of matter to another. Phase changes are physical changes & not chemical changes Occurs with a change of heat (form of energy). Heat energy is either absorbed or released Does NOT change the temperature!
Energy exchanges are not changes in kinetic energy so temperature remains constant. Heat energy is used to change the IM forces between the molecules The amount of energy will depend on the strength of the intermolecular forces.
Phase changes happen when certain points are reached Ex: freezing point = liquid turns into a solid Energy is released as the molecules bond to one another. When it gets colder, most solids shrink in size. Exceptions water expands!
Ex: Melting point = Solid turns into a liquid Ex: a cube of ice sitting on a counter. When a solid reaches the temperature of its melting point it can become a liquid. Energy is required! Added energy is used to break the IM forces between the molecules. Ex: water freezes and melts at 0 C
Ex: Condensation point = gas turns into a liquid When a gas reaches the temperature of its condensation point, it becomes a liquid. Energy is released from the gas particles!
1) 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!
2) 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!
Possible Changes of State: Name Change of State Melting Solid --> Liquid Sublimation Solid --> Gas Freezing Liquid -->Solid Example Ice --> water Dry ice --> CO 2 gas Water --> ice Vaporization Liquid --> Gas Liquid bromine --> bromine vapor Condensation Gas -->Liquid Deposition Gas --> Solid Water vapor --> water Iodine vapor --> Solid Iodine
Vapor = gas phase of a substance that is normally a SOLID or LIQUID at room temperature
C. Evaporation of a Liquid
1) Systems: a) Universe = everything b) System = the part of the universe on which attention is focused c) Surroundings = everything in the universe except the system (usually only concerned with the surroundings near the system)
d) Closed system = system in which matter cannot enter and leave the system (but energy can enter and leave) Ex: Flask with stopper e) Open system = system in which matter can enter and leave the system (also energy can enter and leave) Ex: Open beaker or flask
a) Vaporization = a general term for the process by which a liquid changes to a gas b) Evaporation = 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)
a) particles of a liquid are moving at different velocities and have different KE b) In order for a liquid particle to evaporate (escape into the vapor/gas state) it must: be at the surface of the liquid posses enough KE to overcome the attractive forces (IM forces) holding it in the liquid state
4) Some liquids evaporate more readily than other liquids. a) Volatile Liquid = a liquid that will evaporate readily Ex: Rubbing Alcohol b) Explanation using KMT: There are relatively weak forces 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) Nonvolatile Liquid = a liquid that will evaporate slowly Ex: water d) Explanation using KMT: There are relatively strong forces 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) Boiling = the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point. a) Vaporization occurs throughout b) Molecules in the interior of the liquid form water vapor bubbles c) Water vapor bubbles are less dense than the surrounding liquid and rise to the surface and escape from the liquid.
2) Boiling Point = the temperature at which the equilibrium vapor pressure of the liquid is EQUAL to the pressure exerted on the liquid by the surrounding environmental pressure(often atmospheric pressure). a) If atmospheric pressure is greater than the liquids equilibrium vapor pressure, the bubble will collapse.
3) Equilibrium Vapor Pressure = the pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature A vapor in equilibrium with its liquid contains gas/vapor particles that collide with a surface exerting pressure.
4) Different substances have different equilibrium vapor pressures at a given temperature. KMT Explanation: If equilibrium vapor pressure is high --> substance evaporates readily Substances with a high equilibrium vapor pressure (volatile) typically have weak attractive forces (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). Rubbing Alcohol
If equilibrium vapor pressure is low --> substance does not evaporate readily Substances with a low equilibrium vapor pressure (nonvolatile) typically have strong attractive forces (IM forces) 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
A liquid that boils at a LOW temp. and evaporates rapidly at room temp. is said to be volatile Ex: rubbing alcohol = 82.6 C Ethanol = 78.4 C Acetone = 56 C
As elevation increases (lower atmospheric pressure), boiling point decreases. Cooking time increases at high elevations because food does not get as hot. Ex: Water s boiling points: Sea level- 100 C Denver- 94 C Mt. Everest - 70 C
Ex: Making a cup of tea:
Evaporation: Is a surface phenomenon Particles escape from the surface of a nonboiling liquid and enter the gaseous state
Boiling: At the boiling point, the equilibrium vapor pressure is EQUAL to atmospheric pressure so bubbles form Vaporization occurs throughout Liquid will NOT boil if its equilibrium vapor pressure is lower than the atmospheric pressure!
1) Any vaporization (including evaporation) can be represented as follows: liquid + heat energy (endothermic process) vapor
2) Condensation can be represented as follows: vapor liquid + heat energy (exothermic process)
3) Equilibrium = a dynamic condition in which two opposing physical or chemical changes occur at equal rates in a given closed system
4) A liquid-vapor system at equilibrium can be represented as follows: liquid + heat energy vapor a) If the system is at equilibrium, 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).
a) Only liquid is present but particles begin to evaporate.
b) Evaporation continues at the same rate. There is a relatively low concentration of vapor. Vapor particles are condensing to liquid at a lower rate than evaporation.
c) Concentration of vapor has increased to the point at which the rates of evaporation and condensation are equal. Equilibrium has been reached; the number of particles leaving the liquid equals the number reentering the liquid.
1) 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 a) A stress is usually a change in concentration, temperature, or pressure. 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 concentration: In the equation: 2NO (g) + O 2(g) 2NO 2(g) If you add more NO (g) the equilibrium shifts to the right producing more NO 2(g) If you add more NO 2(g) the equilibrium shifts to the left producing more NO (g) and O 2(g)
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 = LEFT Reasoning = to consume some of the added NO
4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) + energy 2) Removal of O 2 (g) Shift = LEFT 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. RIGHT Equilibrium shifts to the The new equilibrium will contain more vapor particles. The new equilibrium will contain less liquid particles
1) Phase Diagram = a graph of pressure versus temperature that shows which phase a substance exists in under different conditions of temperature and pressure.
a) Can be used to predict what phase any substance will be in for any combination of temperature and pressure.
b) What phase of matter would carbon be in at 5000 C and 10 4 atm? Liquid
2) Triple Point = indicates the temperature and pressure conditions at which the solid, liquid, and gas (vapor) of a substance can coexist at equilibrium
Video w/ explanations: http://www.sciencechannel.com/tvshows/outrageous-acts-ofscience/videos/mysterious-chemicaltriple-point/ Same video w/out explanations: https://www.youtube.com/watch?v=r3zp9 Rj7lnc
3) Critical Point = indicates the critical temperature and critical pressure above which a substance cannot exist in the liquid state no matter what pressure is applied
4) What is the triple point of water? 0.0098 C, 6.0 X10-3 atm
5)What phase of matter would water be in at 1 atm and 375 C? GAS
6) What phase of matter would water be in at 0.75 atm and 50 C? LIQUID