Ch. 8 – phases: gases,liquids,and solids

I. Gases

1.Pressure Barometer measures atmospheric pressure Manometer measures contained gas pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm =760 mm Hg =760 torr 无液气压计；无液晴雨表

2. Ideal Gas 理想气体 There are no forces of attraction between the gas molecules in an ideal gas. The volume of an ideal gas particle is insignificant when compared with the volume in which the gas is contained. Gas molecules are in constant motion, perfect elastically colliding with one another and with the walls of their container. *Real gas tends to be ideal at low pressure and high temperature

克拉伯龙方程 PV = nRT The Ideal Gas Equation P = pressure of the gas(atm) V = volume of the gas (L) n = number of moles of gas T = absolute temperature of the gas (K) R = gas constant 8.31441 J/(mol·K) 0.0821 Latm/(molK)

3. Laws of Ideal Gas P V T

A. Avogadro’s Law Equal volumes of gases contain equal numbers of moles at constant temp & pressure true for any gas V n

V1/n1=V2/n2 ρ1/M1= ρ 2/M2 Avogadro’s Law: At same Temperature and Pressure V1/n1=V2/n2 at STP (P = 1atm = 760 torr, T = 273K), volume of any 1 mole gas = 22.4L. ρ1/M1= ρ 2/M2

B. Boyle’s Law The pressure and volume of a gas are inversely related at constant mass & temp PV = k P V

Boyle’s Law : if the n and temperature are constant P1V1 = P2V2

C. Charles’ Law The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure V T

Charles’s Law: if the n and pressure is constant V1/T1=V2/T2

D. Gay-Lussac’s Law The Pressure and absolute temperature (K) of a gas are directly related. at constant mass & volume P T

Gay-Lussac’s Law: if the n and volume is constant P1/T1=P2/T2

Ex1: A gas occupies 473 cm3 at 36℃. Find its volume at 94 ℃. V1/T1=V2/T2 V2 = 562 cm3

Ex2: PV = nRT L mol Latm/molK K P = 3.01 atm Calculate the pressure in atmospheres of 0.412 mol of He at 16 ℃ & occupying 3.25 L. R = 8.31441 J/(mol·K) 0.0821 Latm/(molK) PV = nRT P(3.25)=(0.412)(0.0821)(289) L mol Latm/molK K P = 3.01 atm

4. Two More Laws

A. Graham’s Law of Diffusion&Effusion

B. Dalton’s Law of Partial Pressure The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases. When a H2 gas is collected by water displacement, the gas in the collection bottle is actually a mixture of H2 and water vapor.

Dalton’s Law of Partial Pressure Ptotal = P1 + P2 + ...

EX3： A gas mixture contains three times as many moles of O2 as N2. Addition of 0.30 mol of argon to this mixture increases the pressure from 1.2 atm to 1.5 atm. How many moles of O2 are in mixture? (A) 0.3 (B) 0.6 (C) 0.9 (D) 1.2 (E) 1.125 √

III Liquids & Solids

1.Liquids vs. Solids IMF Strength Fluid Density Compressible Diffusion Stronger than in gases Y high N slower than in gases SOLIDS Very strong N high extremely slow

2. Liquid Properties Surface Tension 表面张力 attractive force between particles in a liquid that minimizes surface area

3. Types of Solids 晶体Crystalline - repeating geometric pattern covalent network metallic ionic covalent molecular 非晶体Amorphous - no geometric pattern decreasing

Ⅳ. Phase Changes

The transformation of a matter from one phase or state to another one by heat transfer and/or change of pressure.

Evaporation 蒸发 molecules at the surface gain enough energy to overcome IMF Volatility 挥发性 measure of evaporation rate depends on temp & IMF

Vapor Pressure 饱和蒸汽压 The pressure exerted by these molecules as they escape from the surface. When the liquid or solid phase of a substance is in equilibrium with the gas phase, the pressure of the gas will be equal to the vapor pressure of the substance. It depends only on itself property and surrounding temperature.So, for a same substance, as temperature increases, the vapor pressure of a liquid will increase. When the vapor pressure of a liquid increases to the point where it is equal to surrounding atmospheric pressure, the liquid boils.

Patm b.p. IMF b.p. Boiling Point 沸点 temp at which v.p. of liquid equals external pressure depends on Patm & IMF Normal B.P. - b.p. at 1 atm Patm b.p. IMF b.p.

Sublimation 升华 solid  gas v.p. of solid equals external pressure EX: dry ice, mothballs, solid air fresheners

A. Heating Curves

change in KE (molecular motion) depends on heat capacity Temperature Change change in KE (molecular motion) depends on heat capacity KE kenetic energy分子动能 Heat Capacity energy required to raise the temp of 1 gram of a substance by 1°C Heat and changes in phase：Q=mc △T The specific heat of water = 4.18 Jg oC

PE potential energy分子势能 Phase Change change in PE (molecular arrangement) temp remains constant PE potential energy分子势能 Heat of Fusion (Hfus) energy required to melt 1 gram of a substance at its m.p.

Heat of Vaporization (Hvap) energy required to boil 1 gram of a substance at its b.p. usually larger than Hfus…why?

C. Phase Diagrams 相图 水的相图

Phase Diagrams