SC7 - Types of Substance ✓ Flashcards Preview

Edexcel GCSE Chemistry COPY > SC7 - Types of Substance ✓ > Flashcards

Flashcards in SC7 - Types of Substance ✓ Deck (17)
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1

SC7a - What is a compound?

Atoms of more than one element joined together by chemical (covalent) bonds

2

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

3

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

4

SC7a - What are polymers and monomers?

  • Monomers are small simple molecules.
  • When multiple of these join up in a chain, they form a polymer

5

SC7b - What are allotropes?

Different structural forms of the same element

6

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

7

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

8

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

9

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

10

SC7b - Whare are diamond and graphite examples of?

Giant molecular structures: Huge 3D netwroks of atoms linked by bonds

11

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

12

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

13

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

14

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

15

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

16

SC7d - What are the advantages and disadvantages of using metallic models?

Pros:

  • Shows it is held in a lattice
  • Explains properties such as eletical conductivity

Cons:

  • Doesn't show the ions to be constantly vibrating

17

SC7d - What are the advantages and disadvantages of using 3D ball and stick diagrams?

Pros:

  • They show the structure that is formed
  • They show the number of bonds per atom

Cons:

  • The atoms are too far apart
  • There aren't actually any 'sticks'