Presentation on theme: "States of Matter The Solid State"— Presentation transcript:
1States of MatterThe Solid StateParticles are tightly packed, very close together (strong cohesive forces)Low kinetic energy (energy of motion)Fixed shape and volumeCrystalline or amorphous structure
2The Liquid StateParticles are close to each other (making them mostly incompressible)Attractive forces keep molecules close, but not so close to restrict movement
3Gas particles move randomly and rapidly. The Gas StateGas particles move randomly and rapidly.Size of gas particles is small compared to the space between the particles.Gas particles exert no attractive forces on each other.Kinetic energy of gas particles increases with increasing temperature.3
5Pressure (P) is the force (F) exerted per unit area (A). Gases and PressureWhen gas particles collide with the walls of a container, they exert a pressure.Pressure (P) is the force (F) exerted per unit area (A).ForceFPressure==AreaA760. mm Hg760. torr1 atmosphere (atm) =14.7 psi101,325 Pa5
6Gas LawsMathematical relationships describing the behavior of gases with regard to mixing, diffusion, changes in pressure, changes in temperatureBoyle’s Law: Describes the relation between pressure and volume of a gas, under a constant temperaturePiVi = PfVfwhere i = initial condition and f = final condition
7Boyle’s Law: Inverse relation between Pressure and Volume
8Example:Freon-12, CCl2F2, is used in refrigeration systems. What is the new volume (L) of a 8 L sample of Freon gas initially at 50 mm Hg after its pressure is changed to 200 mm Hg at constant T?Set up a data tableConditions 1 Conditions 2P1 = 50 mm Hg P2 = 200 mm HgV1 = 8 L V2 = ?
92. Solve Boyle’s Law for V2: P1V1 = P2V2V = V1P1P2V2 = 8 L x 50 mm Hg = L200 mm Hg
10Learning CheckA sample of helium gas has a volume of 6.4 L at a pressure of atm.What is the new volume when the pressure is increased to 1.40 atm (T constant)?
11Solution P1V1 = P2V2 Solve for V2: V2 = V1P1 P2 V2 = L x atm = L1.40 atmVolume decreases when there is an increase in the pressure (Temperature is constant).
12Learning CheckA sample of oxygen gas has a volume of 12.0 L at 600. mm Hg. What is the new pressure when the volume changes to 36.0 L? (T and n constant.)
13Solution Conditions 1 Conditions 2 P1 = 600. mm Hg P2 = ? V1 = L V2 = LP2 = P1 V1V2600. mm Hg x L = mm Hg L
14Charles’ Law: Describes relation between temperature and volume of a gas, under constant pressure Vi/Ti = Vf/TfCharles’s Law: Direct relationship between Volume and Temperature
16Example:A balloon has a volume of 785 mL at 21°C. If thetemperature drops to 0°C, what is the new volume of theballoon (P constant)?Set up data table:Conditions 1 Conditions 2V1 = 785 mL V2 = ?T1 = 21°C = 294 K T2 = 0°C = 273 KBe sure that you always use the Kelvin (K)temperature in gas calculations!
172. Solve Charles’ law for V2 V1 = V2T T2V2 = V1 T2T1V2 = 785 mL x K = 729 mL294 K
18Learning CheckA sample of oxygen gas has a volume of 420 mL at a temperature of 18°C. At what temperature (in °C) will the volume of the oxygen be 640 mL (P and n constant)?
19Solution T2 = T1V2 V1 T2 = 291 K x 640 mL = 443 K 420 mL = 443 K – 273 K = 170°C
21Combined Gas Law: Describes relation between pressure, temperature and volume of a gas PiVi/Ti = PfVf/Tf
22Example:A sample of helium gas has a volume of L, a pressure of atm and a temperature of 29°C. At what temperature (°C) will the helium have a volume of 90.0 mL and a pressure of 3.20 atm (n constant)?1. Set up Data TableConditions 1 Conditions 2P1 = atm P2 = atmV1 = L (180 mL) V2 = 90.0 mLT1 = 29°C = 302 K T2 = ?
232. Solve for T2 P1 V1 = P2 V2T1 T2T2 = T1 P2V2P1V1T2 = 302 K x atm x mL = K0.800 atm mLT2 = 604 K – = °C
24Learning CheckA gas has a volume of 675 mL at 35°C and atm pressure. What is the volume(mL) of the gas at –95°C and a pressure of 802 mm Hg (n constant)?
25Solution Data Table T1 = 308 K T2 = -95°C + 273 = 178K V1 = 675 mL V2 = ?P1 = 646 mm Hg P2 = 802 mm HgSolve for V2V2 = V1 P1 T2P2T1V2 = mL x 646 mm Hg x 178K = mL mm Hg x 308K
26Pressure and temperature are directly related Gay–Lussac’s Law: Describes the relation between pressure and temperature of a gas, at a constant volumePressure and temperature are directly relatedPressureP= constant= kTemperatureTP1P2=T1T2Note: Temperature must be expressed in kelvins.26
28Avogadro’s Law: Equal volumes of gases measured at the same temperature and pressure contain equal number of moleculesVi/ni = Vf/nfwhere n = number of moles
29Avogadro’s Law Example: If 0.75 mole of helium gas occupies a volume of 1.5 L, what volume will 1.2 moles of helium occupy at the same temperature and pressure?Conditions 1 Conditions 2V1 = 1.5 L V2 = ?n1 = mole He n2 = 1.2 moles HeV1/n1 =V2/n2V2 = V1n2 n1 V2 = L x moles He = L0.75 mole He
30Ideal Gas Law: Describes relation between pressure, volume, temperature and the number of molecules in an ideal gas samplePV = nRTwhere R = universal gas constant ( L atm/K mol)
31Ideal Gas Law Example:A cylinder contains 5.0 L of O2 at 20.0°C and 0.85 atm. How many grams of oxygen are in the cylinder?P = 0.85 atm, V = 5.0 L, T = 293 K, n (or g =?)PV = nRT n = PVRT= (0.85 atm)(5.0 L)(mole K) = mole O2(0.0821atm L)(293 K)= mole O2 x g O2 = 5.8 g O21 mole O2
32Partial Pressure: Pressure an individual gas in a mixture would exert were it alone in the same containerDalton’s Law: Total pressure exerted by a mixture of gases equals the sum of the partial pressuresP(total) = P(gas 1) + P(gas 2) + P(gas 3) etc.
35Intermolecular Forces Intermolecular forces: attractive forces that exist between molecules.In order of increasing strength, these are:London dispersion forcesdipole–dipole interactionshydrogen bonding35
36London Dispersion Forces London dispersion forces: weak interactions due to the momentary changes in electron density in a molecule.Change in electron density creates a temporary dipole.The weak interaction between these temporary dipoles constitutes London dispersion forces.All covalent compounds exhibit London dispersion forces.The larger the molecule, the larger the attractive force, and the stronger the intermolecular forces.36
37Dipole-dipole interaction: attraction between positive end of one polar molecule and negative end of a different polar molecule
38Hydrogen bonding: Specific type of dipole-dipole force, between the partial positive charge on H and partial negative charge on an electronegative element such as O, N, F
40Intermolecular Forces: Boiling Point and Melting Point Boiling point: temperature at which a liquid is converted to a gasMelting point: temperature at which a solid is converted to a liquidThe stronger the intermolecular forces on a substance, the higher its boiling point and melting point are.40
41Examples of Intermolecular Forces and Boiling, Melting Points: 41
42Both molecules have London dispersion forces and nonpolar bonds. In this case, the larger molecule will have stronger attractive forces.42
43Evaporation: the conversion of liquids into the gas phase. Vapor PressureEvaporation: the conversion of liquids into the gas phase.Evaporation is endothermic—it absorbs heat fromthe surroundings.Condensation: the conversion of gases into the liquid phase.Condensation is exothermic—it gives off heat tothe surroundings.43
44Viscosity and Surface Tension Viscosity: a measure of a fluid’s resistance to flow freelyCompounds with strong intermolecular forcestend to be more viscous than compounds with weaker forces.Substances composed of large molecules tend to be more viscous, too, because large molecules do not slide past each other as freely.44
45Interior molecules in a liquid are surrounded by Surface tension: a measure of the resistance of a liquid to spread out.Interior molecules in aliquid are surrounded byintermolecular forces onall sides.Surface molecules onlyexperience intermolecularforces from the sides andfrom below.45
46The Solid State: Types of Solids Crystalline solid: has a regular arrangement of particles—atoms, molecules, or ions—with a repeating structure.There are four different types of crystalline solids— ionic, molecular, network, and metallic.46
47Ionic solid: composed of oppositely charged ions Crystalline SolidsIonic solid: composed of oppositely charged ionsMolecular solid: composed of individual molecules arranged regularly47
48Network solid: composed of a vast number of atoms covalently bonded together (SiO2). Metallic solid: a lattice of metal cations surrounded by a cloud of e− that move freely (Cu).4848
49They can be formed when liquids cool too quickly Amorphous SolidsAmorphous solid: has no regular arrangement of its closely packed particles.They can be formed when liquids cool too quicklyfor regular crystal formation.Very large covalent molecules tend to formamorphous solids, because they can become folded and intertwined.Examples: rubber, glass, and plastic.49