Topic 2

Question 1

What is ionic bonding ?

Answer 1

Ionic bonding is the electrostatic attraction between positive and negative ions

It is a relatively strong attraction

Question 2

How are ionic compounds held together ?

Answer 2

• They are held together in a giant lattice
• Its a regular structure that extends in all directions in a substance
• Electrostatic attraction between positive and negative ions hold the structure together

Question 3

State properties of ionic substances

Answer 3

• high melting and boiling point (strong electrostatic forces between oppositely charge ions)
• Do not conduct electricity when solid (ions in fixed positions)
• Conduct electricity when molten or dissolved in water - ions are free to move

Question 4

How are ionic compounds formed ?

Answer 4

Reaction of a metal with a non-metal

Question 5

What is covalent bond ?

Answer 5

Covalent bond is a shared pair of electrons between two atoms

Question 6

Describe the structure and properties of simple molecular covalent substances

Answer 6

• Do no conduct electricity (no ions)
• Small molecules
• Weak intermolecular forces, therefore: low melting and boiling points

Question 7

How do intermolecular forces change as the mass/size of the molecules increases ?

Answer 7

They increase. That causes melting and boiling points to increase as well (more energy needed to overcome these forces)

Question 8

What are polymers ?

Answer 8

Polymers are very large molecules (>100s , 1000s of atoms) with atoms linked by covalent bonds

Question 9

What are giant covalent substances? Give examples

Answer 9

• Solids , atoms covalently bonded together in a giant lattice
• High melting and boiling points - strong covalent bonds
• Mostly don’t conduct electricity (no delocalised electron)
• Diamond , graphite , silicon dioxide

Question 10

Describe and explain the properties of allotropes of carbon - Diamond

Answer 10

• Four, strong covalent bonds for each carbon atom
• Very hard (strong bonds)
• Very high melting point (strong bonds)
• Does not conduct electricity (no delocalised electrons)

Question 11

Describe and explain the properties of allotropes of carbon - Fullerenes

Answer 11

• hollow shaped molecules
• based on hexagonal rings but may have 5 or 7 - carbon rings
  -The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.

Question 12

Describe and explain the properties of allotropes of carbon - Graphite

Answer 12

• three covalent bonds for each carbon atom
• layers of hexagonal rings
• high melting point
• layers free to slide as weak intermolecular forces between layers; soft, can be used as lubricant
• conduct thermal and electricity due to one delocalised electron each carbon atom

Graphene - a single layer of graphite

Question 13

Describe and explain the properties of allotropes of carbon - Nanotubes

Answer 13

• cylindrical fullerene with high length to diameter ratio
• high tensile strength (strong bonds)
• conduct electricity (delocalised electrons)

Question 14

What is metallic bonding ?

Answer 14

Forces of attraction between delocalised electrons and nuclei of metal ions

Question 15

Describe properties of metals

Answer 15

• high melting/boiling points (strong forces of attraction)
• good conductors of heat and electricity (delocalised electrons)
• Malleable , soft (layers of atoms can slide over eachother whilst maintaining the attraction forces)

Question 16

What are alloys ? Why are they harder than pure metals?

Answer 16

Mixture of metals with other elements , usually metals

Different sizes of atoms distorts the layers , so they cant slide over each other, therefore alloys are harder than pure metals

Question 17

What are the limitations of the simple model?

Answer 17

There are no forces between spheres and atoms , molecules and ions are solid spheres - this is not true

Question 18

What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?

Answer 18

The strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance . The stronger the forces between the particles the higher the melting point and boiling point of the substance

Question 19

A pure substance will melt or boil at …? What about the mixture?

Answer 19

A fixed temperature

A mixture will melt over a range of temperatures

Question 20

What are the three states of matter ?

Answer 20

Solid, liquid , gas

Question 21

Characteristics of polymers

Answer 21

Most polymers are solids at room temp
The intermolecular forces of attraction bettwen polymer molecules are strong
Polymers have a high meting point