1. IMF’s, Solids, and Liquids
Mr. Kinton Honors Chemistry

2. Recall What do you remember about solids and their structure?
What about liquids and their structure?
Intra-particle forces: Ionic, Covalent, and Metallic bonds

3. Intermolecular Forces
The forces that exist between molecules
Weaker than Intra-particle forces
Determine the properties of liquids such as boiling point
Low boiling point=weaker IMF’s
High boiling point=stronger IMF’s
Same holds true for solids and their melting point

4. Types of Intermolecular Forces
There are 3 types of intermolecular forces in neutral molecules:
London-Dispersion forces
Dipole-dipole forces
Hydrogen Bonding
The 3 are referred to as the van der Waals forces
Each are electrostatic in nature

5. London Dispersion Forces
Caused by electrons repelling one another
Creates a temporary dipole
Strongest in larger molecules
Polarizability: the ability of an atoms electric field to be distorted
Exist in all molecules

6. Dipole-Dipole Forces
Positive end of one molecule is near the negative end of another molecule
Only effective when polar molecules are near each other
Dipole-Dipole forces occur between only polar molecules

7. Hydrogen Bonding
Special type of attraction between a Hydrogen atom and either a F, O, or N atom of an adjacent molecule
Causes higher than usual melting/boiling points
Strongest intermolecular force

8. Ion-Dipole Force Attraction between an ion and a polar molecule
Increases based on charge of the ion or the dipole moment
Important in the formation of solutions

9. Melting/Boiling Points

10. IMF Flow Chart

11. Classification of Matter
Solids
Liquids
Definite shape and volume Rigid, not compressible Molecules are held tightly together Definite molecular arrangement
Definite volume
Takes shape of container
Not compressible
Molecules close together but move rapidly

12. Classification of Matter
Gases
Key Terms
Also known as vapor Does not have a definite shape and volume Can be compressed Molecules are far apart Move at a fast pace
Atoms: small building blocks of matter Molecules: two or more atoms joined together

13. You Try! Classify the following as a solid, liquid, or gas: Oxygen
Hand Soap
Eraser
Nacho Cheese
Gold
Chlorine

14. Vapor Pressure
Vapor Pressure – the pressure exerted by a gas in the space above a liquid or solid (must have a constant value At any temperature the movement of particles into the gas phase occurs continuously. As time passes the number of particles in the gas phase increases, thus increasing the chances that a particle will be recaptured by the surface of the liquid (or solid.) Eventually the number of particles escaping equals the number recaptured.

15. Dynamic Equilibrium
Dynamic equilibrium is the condition in which two opposing processes are occurring simultaneously at equal rates.
A liquid and its vapor are in equilibrium when evaporation and condensation occur at equal rates.
The equilibrium vapor pressure of a liquid is the pressure exerted by its vapor when the liquid and vapor states are in dynamic equilibrium. Also called vapor pressure

16. Vapor Pressure and Temperature
Vapor pressure increases with higher temperature. Higher temperature equals more energy and therefore the more particles escaping the surface. Temperature – A measure of the average kinetic energy of the particles in a substance.

17. Vapor Pressure and Volatility
Volatility – The ability of a substance to evaporate. Substances that are extremely volatile will evaporate more quickly. (Ex: gasoline, alcohols) These substances have weak forces holding the particles together. Substances with high volatility have a high vapor pressure (at room temperature) and therefore have a _____ (low/high) boiling point.

18. Melting Point
The melting point and the freezing point of a substance are always equal The melting point occurs at the point where the vapor pressure of the solid and the liquid are equal.

19. Boiling Point
A liquid boils when its vapor pressure equals the external pressure acting on the surface of the liquid. Boiling point increases with increasing external pressure Normal boiliing point – The boiling point of a liquid at standard pressure (1 atm = 760 torr.)

20. Vapor Pressure Graph At what temperature will water boil at 320 torr?
What is the normal boiling point for diethyl ether?
How low must the pressure be for ethanol to boil at 40 Celsius?

21. Phase Diagrams
Phase diagram: plot of pressure vs. Temperature summarizing all equilibria between phases.
Given a temperature and pressure, phase diagrams tell us which phase will exist.
Any temperature and pressure combination not on a curve represents a single phase.

22. Phase Diagram

23. Phase Diagrams
Curves of a phase diagram:
Vapor-pressure curve: (line AB)the equilibrium between the liquid and the gas phases. Generally as pressure increases, temperature increases.
Curve AC: the equilibrium between the solid and gas phase; the variation in the vapor pressure of the solid as it sublimes at different tempertures.
Melting point curve: (line AD) the equilibrium between the solid and liquid; the change in melting point of the solid with increasing pressure.

24. Phase Diagrams Points of a phase diagram:
Triple point: temperature and pressure at which all three phases are in equilibrium. All three phases exist at this point.
Critical point: critical temperature and pressure for the gas. Beyond this point the liquid and gas phases become indistingushable.
Normal melting point: melting point at standard pressure (1 atm, 760 torr, kPa). Always located on the melting point curve
Normal boiling point: boiling point at standard pressure (1 atm, 760 torr, kPa). Always located on the vapor-pressure curve.

25. Phase Diagrams of H20 and CO2
As pressure increases, the solid phase is favored if the solid is more dense than the liquid.

26. Solutions Are they substances or mixtures?
IMF’s interact between the solute and the solvent
Solute: substance being dissolved
Solvent: substance doing the dissolving

27. How do Solutions form
Attractive forces between solute and solvent are comparable to the individual forces
Solvation: when ions are separated and surrounded by a solvent
Hydrations: solvation when water is the solvent
This is a physical change

28. Energy Of Solution Formation

29. Energy Changes Exothermic Endothermic
heat is released to the surroundings
Spontaneous
Feels warm
heat is absorbed from the surroundings
Can be spontaneous
Feels cold

30. Entropy The amount of disorder in a system
Processes that increase entropy tend to occur spontaneously
Solution formation is favored when entropy increases

31. Solutions and Solubility
Solubility: amount of solute needed to form a saturated solution in a solvent
Saturated: solution that is in equilibrium with undissolved solute
Unsaturated: less solute is dissolved than possible in a solution
Supersaturated: occurs when a solution is heated, more solute is added, then cooled

32. Solubility Curves

33. Factors Affecting Solubility
Solute-Solvent Interactions
Pressure Effects
Temperature Effects

34. Solute-Solvent Interactions
Increase when there are stronger attractions between solute and solvent
Hence “like dissolves like”
Miscible: liquids that mix in all proportions
Immiscible: liquids that do not dissolve each other

35. Pressure Effects Only impacts gases in solution
Increasing pressure causes an increase in gas concentration

36. Temperature Effects
Increase in temperature causes an increase in solid solubility
Increase in temperature causes a decrease in gas solubility

37. Ways of Expressing Concentration
Qualitatively
quantitatively
Dilute: relatively small concentration
Concentrated: large concentration of solute
Mass percentage
Mole fraction
Molarity
Molality

38. Colligative Properties
Properties that depend on the concentration of solute particles
As the number of solute particles increase so do the colligative properties as well
4 Colligative Properties
Vapor Pressure
Boiling-Point Elevation
Freezing-Point Depression
Osmosis

39. Vapor Pressure Pressure exerted by a vapor in a closed container
Nonvolatile: no measurable vapor pressure
Volatile: has a measurable vapor pressure
Adding a nonvolatile will lower the vapor pressure

40. Boiling Point Elevation/Freezing Point Depression
Based on the presence of nonvolatile in the solution
Adding a nonvolatile increases the boiling point, but lowers the freezing point
Adding an electrolyte increases the effect

41. Osmosis
Net movement of solvent toward a solution with higher concentration
Stops when the osmotic pressure can stop the movement of the solvent