Properties of Substances

1. Properties of Substances • Describe the types of bonding covered so far. • Describe the properties that are generally exhibited by substances because of the bonding present • Compare and contrast properties to evaluate the type of bonding a substance will have.

2. Properties of Substances Copy the following into your jotter and write below the table A to F and next to each letter write down the bonding it is most likely to have considering its properties: A) Discrete Covalent B) Metallic C) Covalent network D) Ionic F) Covalent molecule E) A cheeky wee metal

3. Types of bonding • ionic bonding – electrons are transferred from metal to non-metal atoms form positive and negative ions. These oppositely-charged ions are attracted to each other. In a giant lattice of oppositely charged ions [electrostatic attraction] • covalent bonding – electrons are shared betweennon-metal atoms. Two kinds discrete covalent bonding i.e. NH3 or CO2 strong bonds in the molecule [intra-molecular bonding] and weak forces of attraction between molecules [intermolecular bonding • metallic bonding – electrons become delocalized and form a sea of free electrons, which attracts positive metal ions.

4. + + + - - + + - - - + + + - - + + - - - + + + - - strong metallic bonds holds ions together Melting and boiling point: giant structures Substances with giant structures generally have high melting and boiling points because all the atoms are strongly bonded together to form a continuous 3D lattice or structure. A large amount of energy is needed to break these bonds. strong covalent bonds holds atoms together strong ionic bonds holds ions together

5. weak bonds between molecules strong bonds within molecules Melting and boiling point: molecules Simple molecular substances have low melting and boiling points because the forces that hold the molecules together are weak and easily broken. In general, the larger the molecule, the higher the melting and boiling point.

6. Images of the types of bonding

7. Ionic lattices and crystals The structure of the lattice means that the ionic compound forms a crystal. This has flat sides and straight edges. These are crystals of sodium chloride. All ionic compounds form lattices and crystals when solid.

8. Covalent network

12. Tragic videos but I felt sorry for them!

13. Predicting bonding

14. True or false?

15. Conductivity Experiment

16. + + + ions cannot move to carry a charge - - + + - - - + + + - - + + - - - + + + - - + + - - + ions are able to move and carry a charge + + - - - - + + - + - - + + - Conductivity – ionic substances Ionic substances cannot conduct electricity when solid because the ions are bonded together in the lattice. When liquid (molten) or dissolved, however, the ions are able to break free of the lattice.

17. Conductivity – covalent substances Substances with covalent bonding do not conduct electricity because all the outer electrons are fixed in shells. electrons unable to move and carry a charge The exception is graphite, which has free electrons between layers of carbon atoms.

18. metal ions Conductivity – metals Metals can conduct electricity because the sea of delocalized electrons between the metal ions are free to move anywhere in the structure. sea of electrons electrons free to move and carry an electrical charge

19. Bonding and electrical conductivity

20. Many ionic substances dissolve in water because water molecules have a slight electrical charge and can attract the ions away from the lattice. Simple molecular substances are usually insoluble in water but soluble in solvents such as petrol. Solubility Substances with giant covalent or metallic structures generally do not dissolve easily in water or other solvents. This is because dissolving involves breaking bonds, which needs lots of energy.

22. Strength Substances with giant structures are generally hard because a large amount of energy is needed to break ionic, covalent and metallic bonds. • Ionic substances are hard but brittle – when a force is applied, ions with like-charges are brought together. These repulse each other and cause the lattice to shatter. • Covalent substances are hard but brittle – the covalent bonds do not bend but break when enough force is applied. • Graphite is slippery because the weak forces between layers of carbon atoms can easily be broken. • Metals are hard but malleable and ductile – the delocalized electrons allow the metallic bonds to move.

23. - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + - - - - - - + + + + + + Ionic lattices In an ionic compound, millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds. This forms a giant 3D structure called an ionic lattice. - - - + + + - - - + + + - - - + + + - - - + + + - - - + + +

24. - - - - - - + + + + + + + + + - - - - - - - - - + + + + + + - - - - - - + + + + + + + + + - - - - - - - - - + + + + + + - - - - - - + + + + + + + + + force Ionic compounds are brittle – they shatter when they are hit. Strength of ionic compounds repulsion When the lattice is hit, a layer of ions is shifted so that ions with the same charges are lined up together. These like charges repel each other, thereby splitting the lattice.

25. strong bonds cause tight packing weak bonds cause loose packing Density The density of a substance depends on the type and strength of bonding and how the atoms/ions are arranged. Giant substances, especially metals, are dense because the atoms/ions are tightly packed together. Substances with simple molecular structures have lower densities. The weak forces between molecules cannot pull the molecules together tightly.

26. True or false?

27. Effect of structure on properties

28. Glossary covalent bond –A strong bond between two atoms in which each atom shares one or more electrons with the other. delocalized–Electrons that are free to move throughout a structure. In metals, they form a ‘sea of electrons’. ionic bond –The strong electrostatic force of attraction between oppositely charged ions. giant structure –A structure containing millions of atoms or ions bonded together. The structure extends in three dimensions until all available atoms or ions are used up. lattice –A 3D structure of closely packed atoms or ions. metallic bonding –The strong attraction between positive metal ions and a sea of electrons. molecule –A simple structure containing two or more atoms covalently bonded together.

29. Anagrams

30. The effect of bonding on properties

31. Comparing bonding – team game

32. Multiple-choice quiz