1. Chapter 5: States of matter

2. solid states but totally different structures:

3. The kinetic model of matter What is matter? Matter is anything that takes up space and has mass.  With a fixed volume and a definite shape – Solid.  With a fixed volume but an indefinite shape – Liquid  With no fixed volume and no definite shape – Gas Atoms and molecules are moving all the time, slowly in a solid (vibration) and fast in a gas. Let’s look at this in more detail. The 3 “States of Matter”

4. Which picture is which state? Liquid GasSolid

5. The states of matter Solid - the particles in a solid are:  close together, touching  in a regular arrangement or lattice  not able to move freely, but simple vibrate in their fixed positions. Liquid - the particles in a liquid are:  closely together; fixed volume  in an random arrangement  able to move around Gas - The particles in a gas are:  Spread far apart from each other  Able to move randomly  Able to move freely

6. Melting point Boiling Point Change between the states

7. State at r.t.p?  Five types of structures are found in elements and compounds: 1. Simple atomic like Argon 2. Simple molecular like CO 2 3. Giant ionic like NaCl 4. Giant metallic like Fe 5. Giant molecular like SiO 2 NaCl and diamond have different structures although they are both solids at r.t.p

8. The gas state Gas molecules (or atoms) are moving rapidly and therefore have kinetic energy. If we study gas behavior we need to make a few assumptions:  The Gas molecules move rapidly and randomly in their space  The distance between the molecules is much larger than the diameter of the molecules  There is no attraction or repulsion between the molecules  All collisions are elastic – no energy loss in collisions  The temperature relates to the kinetic energy of the molecules

9. Kinetic theory of gases  The gas molecules move rapidly and randomly in the space they occupy;

10. Kinetic theory of gases  The distance between the gas molecules is much greater than then the diameter of the molecules so the volume of the molecules in negligible;

11. Kinetic theory of gases  There are no forces of attraction or repulsion between the molecules;

12. Kinetic theory of gases  All collisions between molecules are elastic;

13. The relation between volume and pressure Boyle’s law: Volume x Pressure = constant

14. Gas properties Boyle’s law: PxV = constant at Isothermal conditions (T is held constant) We say: “the volume of a gas at a constant temperature is inversely proportional to the pressure”

15. The relation between volume and Temperature Charles’ law: Volume / Temperature is constant at Isobaric conditions (p is held constant) We say: “the volume of a gas is at constant pressure is proportional to its temperature”

16. Gas properties Isobaric process = p is held constant We say: “the volume of a gas is at constant pressure is proportional to its temperature”

17. The general gas equation symbol:unit:SI-unit PressurepPaN/m 2 VolumeVm 3 m 3 TemperatureTC/KK No. of molesnmolmol Gas constantRJ K -1 mol -1 ?

18. Try try:  A flask of volume 2.0 dm 3 was found to exert a pressure of 200 kPa at a the temperature of 20 ℃. Calculate the number of moles inside the flask. Ideal gas equation: pV = nRT p is the pressure of the gas in pa V is the volume of the gas in m 3 T is the temperature, in K, of the gas; n is the number of moles of gas; R is the gas constant. 8.31 J K -1 mol -1

19. Real gases vs. Ideal gases The equation and theory applies to the “ideal world” which for most (all) gases does not apply. This means there is a certain error in the calculations or a difference in “measured value” and “calculated value”. But why?  There is always attraction between molecules  We can not ignore the volume of the molecules At very high Temperature and very low Pressure gases approach “ideal gas behavior”

20. Question: Consider the ideal behavior of a gas. Then: 1. Kinetic energy is lost when gas atoms/molecules collide 2. Kinetic energy is lost when the temperature is lowered 3. We volume of the gas atoms/molecules has to be negligible in the volume they occupy 4. Ar behaves more ideally than HF does a) 1 and 2 are correct b) 2 and 3 are correct c) 2,3 and 4 are correct d) 3 and 4 are correct

21. Calculating relative molecular masses Remember?? n = m/M r with: n = no. of moles m = mass in grams M r = relative molecular mass in gmol -1 Now we use pV = nRT And we replace n by m/M r and we get a new gas equation:

22. Try try:  A flask of volume 2.0 dm 3 was found to contain 5.28g of a gas. The pressure in the flask was 200 kPa and the temperature was 20 ℃. Calculate the relative molecular mass of the gas.

23. Practice makes perfect: Consider Ideal gas behavior in a closed system. Which gas has a density of 1.630 g dm -3 at at 298 K and 101 kPa? a) Ne b) Ar c) Kr d) Xe Consider Ideal gas behavior in a closed system. Which gas has a density of 2.893 g dm -3 at 298 K and 101 kPa? a) Cl 2 b) I 2 c) HCl d) He

24. Real gases vs. Ideal gases The equation and theory applies to the “ideal world” which for most (all) gases does not apply. This means there is a certain error in the calculations or a difference in “measured value” and “calculated value”. But why?  There is always attraction between molecules  We can not ignore the volume of the molecules At very high Temperature and very low Pressure gases approach “ideal gas behavior”

25. An experiment gives us an “experimental value” A NaOH + HNO 3 → NaNO 3 + H 2 O B K 2 O + 2HCl → 2KCl + H 2 O C Ba(NO 3 ) 2 + H 2 SO 4 → BaSO 4 + 2HNO 3 D Zn + H 2 SO 4 → ZnSO 4 + H 2

26. The liquid state Thermal energy change to ?? energy

27. From solid to liquid When we heat a solid:  The energy transferred to the solid makes the particles vibrate more vigorously  The forces of attraction between the particles weaken  The solid changed to liquid  This change is called melting

28. From liquid to solid When we cool down a liquid:  The kinetic energy decreases and movement of molecules reduces  The forces of attraction between molecules will increase  The liquid will become solid  The change is called freezing

29. From liquid to gas When we heat a liquid:  The energy transferred to the liquid makes the particles move faster  The forces of attraction between the molecules weaken  The liquid evaporates even below the boiling point  Eventually the liquid boils, when the pressure in the liquid is the same as the surrounding  This process is called (e)vaporation

30. From gas to liquid When we cool down a gas:  The molecules loose kinetic energy so they move around lee quickly  The molecules experience increasing forces of attraction  The gas becomes a liquid  We call this process condensation

31. Vapour pressure vaporization Vapour pressure: Vaporization and condensation

32. waterethanol Which pressure will be higher? A)Pressure 1 B)Pressure 2 C)There is no difference Pressure 1Pressure 2 Vapour pressure in closed cups

33. water Which pressure will be higher? A)Pressure 1 B)Pressure 2 C)There is no difference 20 °C50 °C Pressure 1Pressure 2

34. The solid state NaCl and diamond have different structures although they are both solids at r.t.p The regular repeating arrangement of ions, atoms or molecules is called a crystal lattice.

35. The ionic lattices  3-D of alternating positive and negative ions  Ionic lattice or giant ionic structure

36. Cl - Chloride ion Na + Sodium ion Oppositely charged ions held in a regular 3-dimensional lattice by electrostatic attraction The arrangement of ions in a crystal lattice depends on the relative sizes of the ions

37. Each Na + is surrounded by 6 Cl¯ (co-ordination number = 6) and each Cl¯ is surrounded by 6 Na + (co-ordination number = 6). Oppositely charged ions held in a regular 3-dimensional lattice by electrostatic attraction The arrangement of ions in a crystal lattice depends on the relative sizes of the ions

38. Each Na + is surrounded by 6 Cl¯ (co-ordination number = 6) and each Cl¯ is surrounded by 6 Na + (co-ordination number = 6). Oppositely charged ions held in a regular 3-dimensional lattice by electrostatic attraction The arrangement of ions in a crystal lattice depends on the relative sizes of the ions

39. Melting point very highA large amount of energy must be put in to overcome the strong electrostatic attractions and separate the ions. Strength Very brittleAny dislocation leads to the layers moving and similar ions being adjacent. The repulsion splits the crystal. Electricaldon’t conduct when solid - ions held strongly in the lattice conduct when molten or in aqueous solution - the ions become mobile and conduction takes place. SolubilityInsoluble in non-polar solvents but soluble in water Water is a polar solvent and stabilises the separated ions. Much energy is needed to overcome the electrostatic attraction and separate the ions stability attained by being surrounded by polar water molecules compensates for this The ionic lattices

40. Solid state  The types of structures are found in solids 1. Giant ionic like NaCl, MgO, CaCO 3 2. Giant metallic like Fe, Cu, etc. 3. Giant molecular like SiO 2, diamond 4. Simple molecular like I 2 and C 60 5. Hydrogen bonded like ice C 60, Graphene, NaCl and diamond have different structures although they are all solids at r.t.p

41. BRITTLE IONIC LATTICES ++ + + ++ ++ - - - - -- - - + + ++ IF YOU MOVE A LAYER OF IONS, YOU GET IONS OF THE SAME CHARGE NEXT TO EACH OTHER. THE LAYERS REPEL EACH OTHER AND THE CRYSTAL BREAKS UP.

42. IONIC COMPOUNDS - ELECTRICAL PROPERTIES SOLID IONIC COMPOUNDS DO NOT CONDUCT ELECTRICITY Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONS ARE HELD STRONGLY TOGETHER MOLTEN IONIC COMPOUNDS DO CONDUCT ELECTRICITY Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONS HAVE MORE FREEDOM IN A LIQUID SOLUTIONS OF IONIC COMPOUNDS IN WATER DO CONDUCT ELECTRICITY DISSOLVING AN IONIC COMPOUND IN WATER BREAKS UP THE STRUCTURE SO IONS ARE FREE to move around

43. The ionic lattices  They are hard to scratch, because of strong attractive forces keeping the ions together  Also they are brittle, so easy to brake  High melting points and boiling points  Many are soluble in water  Only conduct electricity when molting (liquid state) or dissolved in water

44. Metallic lattices Sea of electrons surrounding the positive ions

45. Metallic lattices Sea of electrons surrounding the positive ions

46. MALLEABLE CAN BE HAMMERED INTO SHEETS DUCTILE CAN BE DRAWN INTO RODS AND WIRES As the metal is beaten into another shape the delocalised electron cloud continues to bind the “ions” together. Some metals, such as gold, can be hammered into sheets thin enough to be translucent. Metallic properties

47. Special metal: Alloys  Alloy is a mixture of two or more metals or a metal with a non-metal  Example is “brass” which is copper + zinc  Why is brass stronger?  Aluminium is often used  Another one is “bronze”

48. Simple molecular lattice  Substances with a simple molecular structure like I 2 can form crystals  Low melting point because only very little energy is needed to overcome the weak van der Waals forces  Ice is water in the solid state, where hydrogen bonding forms the crystalline lattice Lattice of I 2 Crystals of water

49. Giant molecular structures  Covalently bonded structures with 3-D network  Name: Giant molecular structures or giant covalent structures  We discuss 3: Graphite, Diamond and Silicon(IV) oxide

50. Many atoms joined together in a regular array by a large number of covalent bonds GENERAL PROPERTIES MELTING POINT Very high structure is made up of a large number of covalent bonds, all of which need to be broken if atoms are to be separated ELECTRICAL Don’t conduct electricity - have no mobile ions or electrons but... graphite conducts electricity STRENGTH Hard - exists in a rigid tetrahedral structure Diamond and silica (SiO 2 )... but Graphite is soft Giant molecular structures

51. MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each carbon is joined to four others in a rigid structure Coordination Number = 4 ELECTRICAL NON-CONDUCTOR No free electrons - all 4 carbon electrons used for bonding Diamond

52. MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH SOFT each carbon is joined to three others in a layered structure Coordination Number = 3 layers are held by weak induced dipole-dipole interactions can slide over each other ELECTRICAL CONDUCTOR Only three carbon electrons are used for bonding which leaves the fourth to move freely along layers layers can slide over each other used as a lubricant and in pencils Graphite

53. DIAMONDGRAPHITE

54. MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each silicon atom is joined to four oxygens - C No. = 4 each oxygen atom are joined to two silicons - C No = 2 ELECTRICAL NON-CONDUCTOR - no mobile electrons Silicon(IV) oxide

55. Carbon particles  Carbon is a very useful element in the so called “nano” science  In the right form is can be very strong (think about diamond)  There are a few “allotropes” of carbon we will look in more detail. GraphiteDiamondFullerenesNanotubesGraphene

56. Conserving materials