Structure and properties of substances

Question 1

Bonding of metals

Answer 1

Metallic bonding - a lattice of positive kernels in a sea of delocalised electrons (Free Electron Model)

Question 2

Property 1 :

Answer 2

conduction of electricity - electrons are free to move, so when a potential difference is applied current is created.

Question 3

Property 2 :

Answer 3

heat conduction - the delocalised electrons begin to vibrate when heat is applied and that spreads quickly throughout the metal lattice, this causes a transfer of energy and conduction of heat.

Question 4

Property 3 :

Answer 4

high melting point - the strong electrostatic attraction between the metal nuclei and the sea of delocalised electrons require a large amount of heat to break the bonds (high melting point because to melt it, the bonds need to be broken)

Question 5

property 4 :

Answer 5

shiny - the delocalised electrons can readily vibrate when in contact with light, these vibrations result in the emission of the energy on the visible spectrum which is reflected giving metals a shiny appearance

Question 6

Property 5 :

Answer 6

malleable (bendable) and ductile (able to be made thin) - because of the free flowing lattice, when force is applied the electrons are able to slip over each other without braking the bond - this allowing for the metal to be re-shaped without breaking apart

Question 7

Diagram contents :

Answer 7

• grain A
• grain B
• grain boundary
• foreign substance
• dislocation between grain A and B
• vacant site (same size or bigger than an atom

Question 8

what is a slip :

Answer 8

A slip is when an electrons slides over each other, this can create a grain boundary which stops the electrons from moving (makes the metal stronger, but the metal becomes brittle and will not bend but rather brake).

Question 9

alloy :

Answer 9

two metals are melted together, this creates many grain boundaries and strengthens the metal but makes it more brittle.

Question 10

covalent bonds :

Answer 10

• do not conduct electricity (no potential difference can be created because no electrons are free flowing)
• low melting and boiling points (inter-molecular forces are weak)

Question 11

Graphite and diamond :

Answer 11

• both carbon, but bonded differently

- carbon has weak intermolecular bonds, but strong intramolecular bonds

Question 12

Ionic bonding :

Answer 12

there is a lattice of positive and negative ions held together by electrostatic forces

Question 13

i Property 1 :

Answer 13

very high melting point (the electrostatic forces need to be overcome, and that requires a very high temperature

Question 14

i Property 2 :

Answer 14

brittle (the ions are held into specific positions, this stops the ions are repulsive when being shifted - so the lattice falls apart)

Question 15

i Property 3 :

Answer 15

conductive when molten (when molten there is a sea of delocalised electrons allowing for potential difference, and therefore current flow)