1. Bonding & Properties of Substances
National 5 Chemistry
Topic 7
Bonding & Properties of Substances

2. ammeter or bulb
battery or lab pack
experiments help to find out if substances contain charged particles and whether these particles can move or not
conductivity

3. substances when molten or in solution
metal elements and carbon in the graphite form
ions free to move and carry the current
contain electrons which are free to move
ionic compounds
always conduct
substances
never conduct
contain electrons which are fixed in place
non-metal elements and non-metal compounds

4. physical properties ionic metallic covalent 3 main types
depends on the type of bonding present in a substance
physical properties

5. covalent bonding eg methane
a substance made up of two or more atoms joined together by covalent bonds
produces molecules
electrons shared in pairs
between non - metal atoms
covalent bonding

6. electrical conductivity
methane is a non – conductor of electricity
not attracted to electrodes in a cell
methane is made up of neutral molecules
electrical conductivity

7. melting and boiling point
methane is a gas at room temperature
so methane has a low melting point and boiling point
methane molecules only weakly attracted to each other
they need little energy to move around
melting and boiling point

8. solubility in polar solvents
methane is insoluble in water
so methane and water do not mix + -
methane molecules are not attracted by polar water molecules
solubility in polar solvents

9. solubility in non-polar solvents
so methane is soluble in benzene
methane molecules mix well with non-polar solvents like benzene
solubility in non-polar solvents

10. bigger molecules - 1 liquids solids
stearic acid
solids
sucrose (sugar)
hexane
ethanol
liquids
they have stronger forces of attraction between them, so melting and boiling points are higher
some covalent molecules are much bigger than methane
bigger molecules - 1

11. diamond
silica
they have very high melting and boiling points because all of the bonds have to be broken to move the atoms at all
some molecules (called macromolecules) are made up of a huge covalent network of atoms
bigger molecules - 2

12. ionic bonding positive metal and negative non-metal ions formedNa Cl
eg sodium and chlorine
electrons transferred from metal to non-metal atoms Na Cl
between metal and non-metal atoms Na Cl + -
ionic bonding

13. ionic compounds – melting & boiling point
it is a solid at room temperature
hence sodium chloride has high melting ( 801OC )and boiling points ( 1413OC )
sodium chloride is made of oppositely charged ions arranged in a crystal lattice
the ions attract each other strongly, so it takes a lot of energy to move them about
ionic compounds – melting & boiling point

14. electrical conductivity
an electrolyte
positive electrode
negative electrode - +
sodium chloride solution is an electrical conductor
molten sodium chloride is an electrical conductor
ions are free to move
ionic lattice can be broken up by melting or dissolving
electrical conductivity

15. + -
the polar water molecules are strong enough to pull the ions out of the lattice + -
the ionic lattice can be broken up by polar molecules like water + -
solubility 1

16. solubility 2 sodium chloride is soluble in water+
the ions become surrounded by water molecules -
sodium chloride is soluble in water
the compound dissolves
solubility 2

17. metallic bonding they hold the atoms together
the outer electrons are contributed to a shared ‘pool’ of electrons
delocalised electrons
metal atoms pack closely together
neither covalent nor ionic bonding will give metal atoms a full outer shell
between metal atoms
metallic bonding

18. delocalised electrons moving randomly and holding the atoms together
metallic bonding

19. electrical conductivity
metals are good conductors of electricity - +
they move towards the positive terminal
when a supply of electricity is connected
the delocalised electrons are not fixed in place
electrical conductivity

20. melting point metals have a lower melting point than ionic solids
metal ions in the lattice are not firmly fixed in place
they can be moved around without much difficulty
melting point

21. boiling point metals tend to have a high boiling point
they are held there by the delocalised electrons
it is difficult to remove the metal ions from the lattice
boiling point

22. ductility and malleability
because metal ions in the lattice are not firmly fixed in place
metals are ductile
easily drawn out into wires
ductility and malleability
easily beaten out into shape
metals are malleable

23. solubility chemical properties
the reactions of metals with water (and other substances like oxygen and acids)
many of them react with water
metals do not dissolve in water
solubility

24. more about ions - colour
chromate ions, CrO42-(aq) are yellow
permanganate ions, MnO4- (aq) are purple
copper(II) ions, Cu2+(aq) are blue
nickel(II) ions, Ni2+(aq) are green
some ions in aqueous solution have particular colours
more about ions - colour
many ions in aqueous solution are colourless
sodium Na+(aq)
potassium K+(aq)
sulphate SO42- (aq)
chloride Cl- (aq)

25. more about ions – colour of compounds
green
colourless
copper(II) chromate solution
blue
sodium chloride solution
copper(II) sulphate solution
can be predicted from ion colours
more about ions – colour of compounds

26. more about ions - migration
copper chromate gel (green)
positive ions will migrate (move) towards the negative electrode
more about ions - migration
negative ions will migrate (move) towards the positive electrode
contains Cu2+(aq) & CrO42-(aq) ions

27. more about ions – migration results
a blue colour appears around the negative electrode
a yellow colour appears around the negative electrode
CrO42- (aq) ions are negatively charged
Cu2+ (aq) ions are positively charged
copper chromate gel (green)

28. more about ions chemical changes
when an electric current passes through an electrolyte, it brings about
process called
electrolyte
electrolysis
a solution contain ions which conducts electricity
more about ions

29. copper(II) chloride solution
copper metal – Cu(s)
Cu e Cu
pick up 2 electrons
negative electrode
Cu2+(aq)
copper(II) chloride solution
Cl-(aq)
positive electrode
give away 2 electrons
2 Cl Cl e-
chlorine gas – Cl2(g)