Lesson States of Matter: Liquids and Solids

Nội dung text: Lesson States of Matter: Liquids and Solids

1. States of Matter: Liquids and Solids 1. Comparison of Gases, Liquids, and Solids 2. Phase Transitions 3. Phase Diagrams 4. Properties of Liquids: Surface Tension and Viscosity 5. Intermolecular Forces; Explaining Liquid Properties Pres enta tion of Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 1
2. States of Matter  Comparison of gases, liquids, and solids. – Gases are compressible fluids. Their molecules are widely separated. – Liquids are relatively incompressible fluids. Their molecules are more tightly packed. – Solids are nearly incompressible and rigid. Their Pres molecules or ions enta are in close contact tion of and do not move. Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 2
3. Changes of State  A change of state or phase transition is a change of a substance from one state to another. gas boiling condensation sublimation liquid condensation or Pres deposition enta tion melting freezing of Lect ure solid Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 3
4. Vapor Pressure  Liquids are continuously vaporizing. – If a liquid is in a closed vessel with space above it, a partial pressure of the vapor state builds up in this space. – The vapor pressure of a liquid is the partial pressure of the vapor over the Pres liquid, measured at equilibrium at a given enta tion temperature. of Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 4
5. Vapor Pressure  The vapor pressure of a liquid depends on its temperature. – As the temperature increases, the kinetic energy of the molecular motion becomes greater, and vapor pressure increases. – Liquids and solids with relatively high vapor pressures at normal temperatures are said to be Pres volatile. enta tion of Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 5
6. Ilustration of Vapor Pressure Who’s this? Budda (air pressure) will keep the liquid water down while the heat vaporizes the Budda surface water. Water Pres enta tion of Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 6
7. Ilustration of Vapor Pressure When the vapor Water pressure exceeds Then Budda rises Pres enta the air pressure, and vapor bubblestion of Budda cannot keep form throughout theLect And it boils!ure the liquid water liquid. Outl ines down. , 11– PH 101: PHYSICAL CHEMISTRY 7
8. Boiling Point  The temperature at which the vapor pressure of a liquid equals the pressure exerted on the liquid is called the boiling point. – As the temperature of a liquid increases, the vapor pressure increases until it reaches atmospheric pressure. Pres enta – At this point, stable bubbles of vapor form tion of within the liquid. This is called boiling. Lect ure – The normal boiling point is the boiling point Outl ines at 1 atm. , 11– PH 101: PHYSICAL CHEMISTRY 8
9. Freezing Point  The temperature at which a pure liquid changes to a crystalline solid, or freezes, is called the freezing point. – The melting point is identical to the freezing point and is defined as the temperature at which a solid becomes a liquid. – Unlike boiling points, melting points are affected Pres enta significantly by only large pressure changes. tion of Lect ure Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 9
10. Heat of Phase Transition  To melt a pure substance at its melting point requires an extra boost of energy to overcome lattice energies. – The heat needed to melt 1 mol of a pure substance is called the heat of fusion and denoted Hfus. Pres – For ice, the heat of fusion is 6.01 kJ/mol. enta tion of Lect ure H2O(s) → H2O(l); Hfus = 6.01 kJ Outl ines , 11– PH 101: PHYSICAL CHEMISTRY 10