Master Questions - Types of Substances Flashcards
Describe the structure of an ionic lattice
- Giant ionic lattice
- Regular arrangement of oppositely charged atoms in a grid
Explain why an ionic lattice has a high melting point
- Strong electrostatic attraction
- Between oppositely charged ions
- Requires lots of energy to overcome forces
Explain why an ionic compound conducts electricity when molten or dissolved but not when solid
When they’re molten or dissolved, ions are free to move around and carry charge
Describe examples of simple (covalent) molcecules
- 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
Explain why simple molecules have a low melting and boiling point
- Weak inter-molecular forces, which require little energy to be overcome
Explain why carbon dioxide has a lower boiling point then water
- 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
Describe the structure of different giant covalent structures
(diamond, graphite, fullerenes)
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
Explain why graphite conducts electricity but diamond does not
Graphite has delocalised electrons between layers, which are free to move and carry charge
In diamond, the outer electrons are shared in covalent bonds
Describe the structure of a metal
- Giant lattice
- Of positive ions
- Surrounded by a sea of delocalised electrons
Explain why metals have a high melting point
- There is a strong electrostatic attraction, between positive metal ions and delocalised electrons, which require lots of energy to overcome
Explain why metals conduct electricity
Sea of delocalised electrons which can move and carry charge
Describe the structure of a polymer
A large molecule formed from repeating units called monomers