Master Questions - Types of Substances

Question 1

Describe the structure of an ionic lattice

Answer 1

• Giant ionic lattice

- Regular arrangement of oppositely charged atoms in a grid

Question 2

Explain why an ionic lattice has a high melting point

Answer 2

• Strong electrostatic attraction
• Between oppositely charged ions
• Requires lots of energy to overcome forces

Question 3

Explain why an ionic compound conducts electricity when molten or dissolved but not when solid

Answer 3

When they’re molten or dissolved, ions are free to move around and carry charge

Question 4

Describe examples of simple (covalent) molcecules

Answer 4

• Simple molecules contain only only a few atoms held together by covalent bonds
• An example is carbon dioxide which contains one atom of carbon bonded with two atoms of oxygen

Question 5

Explain why simple molecules have a low melting and boiling point

Answer 5

• Weak inter-molecular forces, which require little energy to be overcome

Question 6

Explain why carbon dioxide has a lower boiling point then water

Answer 6

• Carbon dioxide has very weak inter-molecular forces
• Water has stronger inter-molecular forces between molecules called hydrogen bonds, which require more energy to be overcome

Question 7

Describe the structure of different giant covalent structures
(diamond, graphite, fullerenes)

Answer 7

Diamond - Each carbon is bonded to 4 other carbon atoms, forming a giant covalent structure

Graphite - Each carbon is contently bonded to 3 other carbon atoms, forming layers which are held together by weak inter-molecular forces

Fullerenes - Molecules of carbon atoms with hollow shapes. Their structures are based on hexagonal rings of carbon atoms joined by covalent bonds

Question 8

Explain why graphite conducts electricity but diamond does not

Answer 8

Graphite has delocalised electrons between layers, which are free to move and carry charge
In diamond, the outer electrons are shared in covalent bonds

Question 9

Describe the structure of a metal

Answer 9

• Giant lattice
• Of positive ions
• Surrounded by a sea of delocalised electrons

Question 10

Explain why metals have a high melting point

Answer 10

• There is a strong electrostatic attraction, between positive metal ions and delocalised electrons, which require lots of energy to overcome

Question 11

Explain why metals conduct electricity

Answer 11

Sea of delocalised electrons which can move and carry charge

Question 12

Describe the structure of a polymer

Answer 12

A large molecule formed from repeating units called monomers