Chapter 10: States of Matter

1. Chapter 10: States of Matter Concept Base: Chapter 1: Properties of Matter Chapter 2: Density Chapter 6: Covalent and Ionic Bonding

2. Covalent Vs. Ionic Bonding atoms combine to form ionic bondscovalent bonds (M + NM) (NM + NM) chemical bond – a mutual electrical attraction between the nuclei and valence electrons of two atoms that binds the atoms together

3. Ionic Bonding • ionic bond – when electrons are taken by one atom from another atom metal and a nonmetal NaCl cation and anion

4. Covalent Bonding covalent bond – when electrons are shared between two atoms • two nonmetals • No ions formed! (no electrons are taken) H-H .. .. O H H

5. There is another type of bond, not purely covalent and not purely ionic. Pure Covalent Nonpolar Covalent Polar Covalent Ionic

6. The Kinetic-Molecular Theory of Matter • In reality, all atoms are moving: vibrating, rotating, translating. • The only time something would NOT be moving is at ABSOLUTE ZERO, • (0 Kelvin or -273 oC).

7. The Kinetic-Molecular Theory of Gases • ideal gas – hypothetical gas that perfectly fits all the assumptions of the kinetic-molecular theory. • real gas – a gas that does not fit all the assumptions of the kinetic-molecular theory. Although an ideal gas does not exist, many gases behave nearly ideally if pressure is not very high and temperature is not very low.

8. The Kinetic-Molecular Theory of Gases • Gases consist of large numbers of tiny particles that are far apart relative to their size • Gases take up much more space than solids or liquids • Gases are easily compressed

9. The Kinetic-Molecular Theory of Gases • Collisions between gas particles and between particles and container walls are elastic collisions. • elastic collision – • a collision with no • loss of energy • inelastic collision – • a collision with some • loss of energy

10. The Kinetic-Molecular Theory of Gases • Gas particles are in continuous, rapid, straight-line, random motion. They therefore possess kinetic energy, which is energy of motion. • The KE that the molecules have as a gas overcomes any attractive forces that they might have.

11. The Kinetic-Molecular Theory of Gases • There are no forces of attraction between gas particles.

12. The Kinetic-Molecular Theory of Gases • The temperature of a gas depends on the average kinetic energy (energy of motion) of the particles of the gas

14. The Nature of Gases • Gases do not have a definite shape or volume • They completely fill any container because they have no attraction for the other molecules in the container (unlike liquids and solids).

15. The Nature of Gases • fluid – a nonsolid state of matter in which the atoms or molecules are free to move past each other, as in a gas or liquid (it flows) • In a gas or liquid, attractive forces are insignificant or weaker, thus the particles glide easily past one another and are called fluids.

16. The Nature of Gases • Gases have low densities.

17. The Nature of Gases • Gases can be compressed Thus, many more molecules can be inside a container under great amounts of pressure.

18. The Nature of Gases Gases diffuse readily into one another. Flasks are NOT connected. Valve is opened to connect the flasks.

19. The Nature of Gases diffusion – the spontaneous movement of particles of gas caused by random motion effusion – process by which gas particles pass through a tiny opening due to pressure being exerted upon them

20. KE = ½mv2 • Gas molecules move at different speeds or velocities, depending on • the temperature at which the molecules are • the molar mass of the molecules The higher the MM, the slower they move.

21. Check for Understanding • What kind of states of matter can be poured? • Which molecules are moving faster, water at 50oC or water at 20oC? • Which state(s) of matter can be compressed to great extents?

22. Intermolecular Forcespages 203-207 – Chapter 6 • intermolecular forces - attractive forces between molecules • These forces vary in strength, however are generally much weaker than covalent bonds (not intermolecular). • The stronger the intermolecular force the closer the molecules get to one another, thus perhaps creating a solid versus a liquid, etc.

23. What do you think? • Now that we learned about intermolecular forces, what do you think an intramolecular force is? Give two examples. Intramolecular Forces > Intermolecular Forces (stronger than)

24. Dipole-Dipole Forces • dipole – a molecule or a part of a molecule that contains both partial positive and partial negative regions A dipole is created when there is a large difference in electronegativity.

25. Dipole-Dipole Forces The partial positive end is attracted to the partial negative end.

26. Dipole-Dipole Forces • Compare ICl to Br2 because they have approximately the same molar mass ICl BP = 97oC Br2 BP = 59oC What makes ICl have a higher BP? 162 g/mol 160 g/mol

27. Dipole-Induced Dipole Attraction

28. Dipole-Induced Dipole Attraction Water molecule that is polar Nonpolar molecule that has become polar This is called an induced dipole which is only temporary.

29. Ion-Induced Dipole Attraction

30. Ion-Induced Dipole Attraction This is called an induced dipole which is only temporary.

31. What do you think? Looking at the previous intermolecular forces, do you think it would be possible to have an ion-dipole attraction? Explain.

32. Hydrogen Bonds F-H (HF) O-H (H2O) N-H (NH3) • All of these bonds have a large difference in electronegativity, thus creating a large dipole, or a highly polar bond. • These highly polar bonds have a very strong attraction. • These very strong attractions are called hydrogen bonds.

33. Demonstrate water kit

34. Hydrogen Bonds Hydrogen Bonding in Water

35. Hydrogen Bonding in Water • Because of the hydrogen bonding in water, an open, rigid structure is formed when freezing. • As a solid, there is more hydrogen bonding than as a liquid. • Dice at 0oC = 0.917 g/mL • Dwater at 0oC = 1.000 g/mL

36. Hydrogen Bonds Hydrogen Bonding in Acetic Acid HC2H3O2

37. Hydrogen Bonds • Compare H2O to H2S H2O BP = 100oC H2S BP = -61oC • Compare NH3 to PH3 NH3 BP = -33oC PH3 BP = -88oC What makes H2O and NH3 have higher boiling points?

38. HydrogenBonds • Snowflakes are large ice crystals that have a unique shape. The shape reflects the rigid position of the hydrogen bonding of the solid.

41. London Dispersion Forces • Nonpolar molecules will also exhibit a weak attraction for one another. • The constant motion of electrons within a molecule can create a temporary dipole, or London dispersion force, that attracts to another temporary dipole.

42. London Dispersion Forces London forces are dependent upon the motion of electrons. Therefore, the more electrons, the greater the London forces. molar mass­ London forces ­

43. London Dispersion Forces London forces are dependent upon the motion of electrons. Therefore, the more electrons, the greater the London forces.

44. London Dispersion Forces London forces are dependent upon the motion of electrons. Therefore, the more electrons, the greater the London forces.

45. London Dispersion Forces London forces are dependent upon the motion of electrons. Therefore, the more electrons, the greater the London forces.

46. London Dispersion Forces London forces are dependent upon the motion of electrons. Therefore, the more electrons, the greater the London forces. This attraction is called a London dispersion force. How permanent is this attraction?

47. Check for Understanding Compare Cl2, Br2, and I2 and arrange them according to the strength of their London forces. What are their states of matter at room temperature? WHY?

48. Intermolecular Forces Strength of Intermolecular Forces from Highest to Lowest • hydrogen bonding • dipole-dipole attraction • London dispersion forces van der Waals forces

49. Check for Understanding • What physical property directly correlates with the strength of the London dispersion forces? What types of molecules have the strongest intermolecular forces? What do you think accounts for NH3, ammonia, having a boiling point 130oC higher than CH4, methane?

50. Comparison of Boiling Points