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GCSE Edexcel Separate Chemistry > SC7 Types of Substances > Flashcards

SC7 Types of Substances Flashcards

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1
Q

What are giant covalent structures?

A

Structures wherein many covalent bonds have been used to join the substance together

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2
Q

What are the properties of giant covalent substances?

A
  • high melting and boiling points
  • no conduction of electricity
  • insoluble in water
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3
Q

Why do giant covalent substances have high melting and boiling points?

A

They are solids at room temperature, which tells us that the covalent bonds that hold them together are strong and need lots of energy to break

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4
Q

Why can’t giant covalent substances conduct electricity?

A

They carry no overall charge, so they can’t conduct electricity

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5
Q

Why are giant covalent substances insoluble in water?

A

Giant covalent substances can’t form strong attractions with water, so they can’t dissolve in it

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6
Q

What are some examples of allotropes of carbon?

A
  • Diamond
  • graphite
  • graphene
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7
Q

Describe the structure and bonding of diamonds

A
  • each carbon atom is joined to four other carbon atoms through a covalent bond
  • form a regular tetrahedral structure
  • no free electrons
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8
Q

Describe the properties of diamond

A
  • high melting and boiling points
  • doesn’t conduct electricity
  • hard
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9
Q

What are some of the uses of diamond?

A
  • used to cut hard things
  • worn as jewellery
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10
Q

Describe the structure and bonding of graphite

A
  • each carbon atom is joined with three other carbon atom
  • carbon atoms form a hexagonal layered structure
  • layers have weak forces of attraction between them, which means that it can easily slide over each other
  • each carbon atom has one un-bonded outer electron
  • these are the free electrons, and they are delocalised
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11
Q

Describe the properties of graphite

A
  • slippery
  • high melting and boiling points
  • can conduct electricity due to the delocalised electron
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12
Q

What is graphene?

A

A single layer of graphite

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13
Q

What are fullerenes?

A

Molecules of carbon with hollow shapes. Their structures are based on hexagonal rings of carbon atoms.

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14
Q

State two examples of a fullerene

A
  • nanotubes
  • Buckminster balls
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15
Q

What are the properties of a fullerene?

A
  • low melting and boiling points
  • soft
  • slippery
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16
Q

Define polymer

A

A large molecule which is consists of many identical smaller molecules known as monomers

17
Q

What are carbon nanotubes?

A

Cylinder fullerenes with a high length to diameter ratios

18
Q

What are the properties of graphene?

A
  • can conduct electricity due to the delocalised electrons
  • strong
  • high melting point
19
Q

Describe the properties of a Bucky Ball

A
  • consists of weak intermolecular forces which need little energy to overcome
  • lower melting points compared to diamond or graphite
20
Q

Describe the properties of a nanotube

A
  • high tensile strength, so they are strong in tension and can resist being stretched
  • strong
  • can conduct electricity
21
Q

Explain the state most polymers are in at a room temperature

A

They are in a solid state because the intermolecular forces are relatively strong

22
Q

Describe some common properties of metals

A
  • solids with high melting
  • shiny
  • malleable
  • high density
  • good conductors of heat and electricity
23
Q

Describe some common properties of non-metals

A
  • solids, liquids or gases with low melting points
  • not usually shiny when solid
  • brittle
  • low density
  • poor conductors of heat and electricity
24
Q

Describe the structures of graphite and diamond.

A

Graphite
- Giant molecular structure.
- Each carbon atom is bonded to three others.
- Weak intermolecular forces between layers.
- strong covalent bonds between atoms in a layer.
Diamond
- Giant molecular structure.
- Each carbon atom is bonded to four others.
- Strong covalent bonds between atoms.
- High boiling and melting points.

25
Q

Explain the properties of fullerenes including C60 and graphene in terms of their structures and bonding.

A

Graphene
- Each carbon atom is covalently bonded to three other carbon atoms.
- Very strong and flexible.
- Conducts electricity as electrons are free to move.
Fullerene
- Has carbon atoms arranged in pentagons as well as hexagons.
- Conducts electricity as they have delocalised electrons.
- Are soft when in solid state as they have weak intermolecular forces.

26
Q

Explain, in terms of structure and bonding, why graphite is used to make electrodes and as a lubricant, whereas diamond is used in cutting tools.

A
  • Graphite has weak intermolecular forces between layers, so they can slide off each other.
  • Graphite has free electrons which carry a charge, allowing it to conduct electricity.
  • Diamond has strong covalent bonds between atoms.
  • Diamond also has high melting and boiling points
27
Q

Describe the structure and bonding of metals

A

The electrons in the outermost shell ‘leave’ the atom, forming positive ionic lattice in a sea of delocalised electrons

28
Q

Why are metals malleable?

A

Layers of ions can slide over each other without breaking when a force is applied

29
Q

What is metallic bonding?

A

The electrostatic attraction between the metal ions and the sea of delocalised electrons

30
Q

Why can metals conduct electricity?

A

The delocalised electrons move through the lattice when a voltage is applied. This carries the charge forming an electric current

31
Q

What is a bonding model?

A

A description of how a chemical bond is formed and/or the structure produced by atoms

32
Q

What does a dot and cross diagram show?

A
  • how the ionic bonds are formed
  • the ratio in which atoms react
33
Q

What are the limitations of a dot and cross diagram for ionic compounds?

A
  • doesn’t show the ionic lattice
  • doesn’t show the ionic bonds
34
Q

What are the limitations of a chemical formula as a bonding model?

A
  • doesn’t show charges
  • doesn’t show arrangement of atoms
35
Q

What are the limitations of a 2d diagram?

A
  • doesn’t show how bonds were formed
  • doesn’t show the other layers
36
Q

What are the limitations of a 3d diagram?

A
  • doesn’t show the attraction between the molecules
  • isn’t to scale
37
Q

What are the limitations of a ball and stick model?

A

It doesn’t show
- the sticks are actually forces
- how covalent bonds are formed

38
Q

What are the limitations of the space filling model?

A
  • we don’t know which elements are which
  • doesn’t show how the covalent bonds were formed
39
Q

What are the limitations of a dot and cross diagram for covalent bonds?

A

It doesn’t show:
- relative sizes of the molecules
- intermolecular forces

GCSE Edexcel Separate Chemistry (23 decks)

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