SC7 - Types of Substance ✓ Flashcards
SC7a - What is a compound?
Atoms of more than one element joined together by chemical (covalent) bonds
SC7a - Why do simple molecular compounds have low m.p/b.p?
- They are formed of covalent bonds
- While there are strong covalent bonds, the forces between molecules are weak meaning they require little energy to break
SC7a - Why aren’t simple molecular compounds able to conduct electricity?
- For something to be able to conduct electricity it must contain a charged particle that is free to to move.
- Covalent bonds aren’t based on charges tso it doesn’t meet these requirements
SC7a - What are polymers and monomers?
- Monomers are small simple molecules.
- When multiple of these join up in a chain, they form a polymer
SC7b - What are allotropes?
Different structural forms of the same element
SC7b - Describe the structure and properties of a fullerene?
- Fullerenes are spherical or tubular structures where each carbon atom is bonded to three others
- They have low m.p/b.p due to weak intermolecular forces
- They are also soft and slippery
- Can conduct electricity due to delocalised electron
SC7b - Describe the structure and properties of graphene?
- Flat shape that cna be rolled up
- Each carbon atom is bonded to threee others meaning there is a delocalised electron allowing conduction of electricity
- Low m.p/b.p
SC7b - Describe the structure and properties of graphite?
- High melting point due to strong covalent bonds
- Layers easily slide over eachother due to weak forces between them
- Three bonds per carbon atom
- Delocalised electron allows conduction of electricity
- Useful as a lubricant due to layers sliding
- Used for electrolysis as it is unreactive and cheap
SC7b - Describe the structure and properties of diamond?
- Tetrahedral structure
- Four bonds per carbon atom
- Electrical insulatro due to no free electrons
- High melting point due to strong covalent bonds
- Very strong due to tetrahedral structure
- Used for drills due to strength
SC7b - Whare are diamond and graphite examples of?
Giant molecular structures: Huge 3D netwroks of atoms linked by bonds
SC7c - What is metallic bonding?
- Metals are bonded in a giant lattice structure
- They are held together by the stron electrostatic forces of attraction that exist between the positive metal ions and the negative delocalised electons
- Strong electrostatic forces of attraction require a lot of energy to break giving them high m.p/b.p
- Delocalised electron allows it to conduct electricity
- They are also malleabele
SC7c - How are metals malleable?
- Mallebale means that it can change shape and bend without breaking
- Metals are a giant lattice structure of positive metal ions delocalised electrons
- When a force is applied to a metal, the layers slide over each other
- It doesn’t break because of the ‘sea’ of delocalised electrons holding the metal together by electrostatic forces
SC7c - Why are metals able to conduct electricity?
- To be able to conduct electricity, something must contain a charged particle that is free to move
- Since metals have a sea of deloclised electrons, it meets these two requirements
- When a potenital difference is applied, the electrons move to the positive side
SC7c - How does the electrical conductivity of a metal vary?
- As the charge of the ion increases, the number of delocalised electrons per atom increases.
- This increases the electrical conductivity
SC7d - What are the advantages and disadvantages of using dot and cross diagrams?
Pros:
- Shows how electrons are shared in covalent and ionic bonds
Cons:
- Do not show the structure formed
- Suggests that electrons are different
