3.1.3.4 Bonding and Physical Properties

Question 1

What is fusion?

Answer 1

It is when a solid turns into a liquid by supplying more energy. This energy is needed to weaken the forces between molecules

Question 2

What is enthalpy?

Answer 2

The heat energy change

Question 3

What is vaporisation?

Answer 3

A liquid gaining energy and becoming a gas

Enthalpy change of vaporisation is the energy needed to do this

Question 4

What are crystals?

Answer 4

They are solids with a regular structure

Question 5

What are the types of crystals?

Answer 5

Ionic, metallic, molecular, macromolecular

Question 6

Ionic crystals

Answer 6

Have strong electrostatic attractions between oppositely charged ions = high melting points
Requires a lot of energy to seperate the ions

Question 7

Metallic crystals

Answer 7

Exist as a lattice of positive ions embedded in a sea of delocalised electrons
Strong metallic bonds causes high melting temperature

Question 8

Molecular crystals?

Answer 8

Consists of molecules held in a regular array by intermolecular forces
Covalent bonds within the molecules hold the atoms together but they do not act between the molecules
Intermolecular forces are weaker so they have lower melting points and low enthalpies of melting

Question 9

What is the structure of iodine?

Answer 9

Macromolecular crystal
Stong covalent bonds join ioding atoms to form I2
Iodine has a large number of electrons so van der waals forces are strong
Crystals are soft and break easily
Low melting temperature
Doesn’t conduct electricty

Question 10

What are macromolecular crystals?

Answer 10

When covalent bonds extend throughout the structure

High melting points

Question 11

Diamond

Answer 11

Macromolecular structure
Each carbon atom forms four covalent bonds with other carbon atoms
Tetrahedron with bond angles of 109.5
Very hard material
Very high melting point
Doesn't conduct electricity

Question 12

Graphite

Answer 12

Layers of flat trigonal pyramids
Carbons are held together by strong bonds
This creates a strong connection along the layers
This leaves a free electron in a p-orbital which becomes delocalised and carries charge
Weak Van der Waals forces between layers
Soft material
High melting temperature because of the covalent bonds
Conducts electricity along the layers

Question 13

What is the name of bromine bonding?

Answer 13

Simple molecular