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GCSE Chemistry Unit 2 > Bonding, Structure and Properties > Flashcards

Bonding, Structure and Properties Flashcards

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1
Q

What are the properties of metals? (9)

A
  • high lustre
  • grey
  • ductile
  • malleable
  • high melting/boiling point
  • high density
  • sonorous
  • good conductors
  • insoluble in water
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2
Q

What are the properties of ionic compounds? (4)

A
  • high melting/boiling point
  • conducts electricity when molten or aqueous
  • brittle
  • are soluble in water
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3
Q

What are the properties of simple molecular covalent substances? (3)

A
  • low melting/boiling point
  • does not conduct
  • insoluble in water
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4
Q

What are the properties of giant covalent substances? (4)

A
  • high melting/boiling point
  • (diamond) does not conduct
  • (graphite) conducts when solid
  • insoluble in water
  • strong structure (particularly diamond)
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5
Q

Describe the structure of metals (2)

A

Lattice of cations in a sea of delocalised electrons

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6
Q

Why are metals good conductors?

A

Sea of delocalised electrons - are free to move around the lattice of cations, so they can easily transfer electricity and heat.

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7
Q

Why are metals malleable/ductile?

A

They are a lattice of cations - when force is applied the layers of metal atoms slide over one-another.

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8
Q

Why do metals have a high melting/boiling point?

A

The metallic bond is strong and requires a lot of energy to be broken. It is the force of attraction between the delocalised electrons and the cations.

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9
Q

What is the trend in melting points of metals as you move from group 1 to group 3 of the periodic table. And why?

A

The melting points increase from group 1 to group 3. Because group 3 has 3 delocalised electrons per atom so there is a stronger force of attraction between the cations and the electrons and a stronger metallic bond that requires more energy to break.

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10
Q

What is ionic bonding represented with?

A

Dot and Cross diagrams

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11
Q

What is an ionic compound made up of?

A

A metal and a non-metal

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12
Q

In ionic bonding, what type of ions do metals form?

A

positive ions (cations)

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13
Q

In ionic bonding what types of ions do non - metals form?

A

negative ion (anion)

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14
Q

What happens in ionic bonding in terms of electronic structure? (3)

A
  • Metals transfer their electrons to non-metals.
  • The metals lose electrons to gain a full outer shell, to be more stable.
  • The non - metals gain electrons to have a full outer shell, to be more stable.
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15
Q

How would you create a dot and cross diagram for ionic bonding?

A

1) Find the elements electronic structure
2) Find how many electrons they gain/lose & what ions they form
3) Find the ratio needed
4) Draw the outer shell of the atoms (label the atoms) with the electronic structure in brackets below.
5) Circle the electron the atom is losing and draw an arrow to the place in the other atom where it will go.
6) Draw the ions in brackets with the charge on the outside and electronic structure in brackets below.
7) There will be nothing the metal ion but the non-metal ion will have a full outer shell of dots and crosses.

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16
Q

What is an ionic bond? (1)

A

A strong electrostatic force of attraction between the positively charged metal ions and negatively charged non-metal ions.

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17
Q

Describe the structure of an ionic compound (1)

A

Giant ionic lattice (a lattice of cations and anions)

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18
Q

Explain why ionic compounds have a high melting/boiling point (2)

A

Ionic bonds are strong and require a large amount of energy to break them. The ionic bond is the force of attraction between the cations and anions in the giant ionic lattice.

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19
Q

Why are ionic compounds soluble in water?

A

Polar water molecules surround and attract the cations and anions in the giant ionic lattice, breaking the bonds and pulling ions into the solution.

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20
Q

Explain why ionic compounds conduct electricity when aqueous or molten. (2)

A
  • When molten the ions are free to move to conduct the electric current
  • When aqueous the ions are separated and free to move to conduct the electric current.
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21
Q

How does the charge of ions in ionic compounds affect boiling/melting points? (2)

A
  • The greater the charge on the ions, the greater the electrostatic force/ stronger the ionic bond.
  • Stronger ionic bonds, require more energy to break them, leading to higher melting/boiling points.
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22
Q

What are covalent compounds made up of?

A

non-metals

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23
Q

What are the two types of covalently bonded substances? (2)

A
  • Giant covalent substances
  • Simple covalent substances (Simple molecular substances)
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24
Q

How are covalent bonds formed?

A

Covalent bonds are formed when non-metal atoms share one or more pairs of electrons to attain a full-outer shell of electrons, to be stable.

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25
Q

Describe how to draw a dot and cross diagram for covalent bonding. (5)

A

1) Find the electronic configuration of each atom.
2) establish how many electrons each atom needs to have a full outer shell.
3) draw the outer shells overlapping each other (like a Venn diagram).
4) use dots for one elements electrons and crosses for the others.
5) place electrons in the overlapping sections o that each outer shell is full.
6) Write the bond notation below (e.g. 0=C=0)

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26
Q

What is a covalent bond?

A

The force of attraction between shared electrons and the nuclei of atoms.

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27
Q

What is a triple covalent bond?

A

When three pairs of electrons are shared between the atoms to achieve a full outer shell

28
Q

What is a double covalent bond

A

When 2 pairs of electrons are shared between the atoms to achieve a full outer shell.

29
Q

Are covalent bonds between atoms strong?

A

Yes

30
Q

Why do simple covalent/ simple molecular substances have low melting/boiling points? (2)

A
  • Simple molecular substances have weak intermolecular forces between molecules that require a low amount of energy to break
  • so they have low melting/boiling points.
31
Q

Why do simple covalent/simple molecular substances not conduct electricity when solid or molten? (3)

A

-They have no free moving electrons,
- ions
- and the molecules have no overall charge in any state of matter
so they cannot conduct electric charge.

32
Q

What does allotrope mean?

A

Different physical forms of the same substance

33
Q

What are all of the giant covalent structures you need to know about? (5)

A
  • diamond
  • graphite
  • fullerenes
  • carbon nano-tubes
  • graphene
34
Q

What do diamond and graphite both have very high melting points?

A

They both contain strong covalent bonds between carbon atoms

35
Q

Why does graphite have brittle, lubricating, conductive properties when diamond does not? And why is diamond harder than graphite?( 3)

A
  • Each carbon atom in diamond is strongly bonded to 4 others
  • Whilst, each carbon atom in graphite forms only 3 strong bonds
  • so the graphite carbon atoms’ 4th electron is delocalised
36
Q

What are fullerenes?

A

Cage structures made entirely of carbon atoms

37
Q

What is the most widely known fullerene?

A

Buckminster fullerene

38
Q

What is the structure of Buckminsterfullerene?

A

Its’ molecules are spherical and contain 60 carbon atoms

39
Q

What are fullerenes used for? (or rather research is being led into these uses at the moment) (3)

A
  • drug delivery systems in the body
  • lubricants
  • catalysts
40
Q

What are the important properties of nano-tubes? (3)

A

They are:
- conductors/semi-conductors
- high strength
- low density

41
Q

Explain why nano-tubes are conductors/semi-conductors in terms of structure?

A

Each carbon atom forms 3 covalent bonds with other carbon atoms. So the 4th electron is delocalised and free to carry electrical charge.

42
Q

Explain why carbon nano-tubes have high strength?

A

The bonds present between the carbon atoms are strong covalent bonds.

43
Q

Explain why carbon nano-tubes have very low density?

A

They are hollow tubes, made of a single sheet of graphene (one layer of carbon atoms), so they are very light.

44
Q

are carbon nano-tubes of a larger or smaller scale than carbon fibres?

A

Much smaller scale

45
Q

What has graphene been shown to be? (2)

A
  • The strongest material ever tested
  • The best electrical conductor
46
Q

Claims have been made that graphene will transform technology in the future. How have these fared, as of yet?

A

At the moment there are no commercially available ‘graphene products’

47
Q

Do individual atoms have the same properties as bulk materials?

A

NO

48
Q

What materials/substances demonstrate that individual atoms do not have the same properties as bulk materials?

A
  • diamond, graphite, fullerenes,
    carbon nano-tubes and
    graphene (all contain only carbon atoms, but have different properties)
  • nano-scale silver particles and bulk silver (they have different properties)
49
Q

What are the properties of nano-scale silver particles? (3)

A
  • antibacterial
  • antiviral
  • antifungal
50
Q

What are the uses of nano-scale silver particles? (5)

A
  • plasters
  • antiseptic sprays
  • refrigerator linings
  • socks
  • deodorant sprays
51
Q

Why are nano-scale titanium dioxide particles used in some sun screens? (2)

A

They:
- absorb and reflect UV light
- transparent

52
Q

What are the uses of nano-scale titanium dioxide particles? (2)

A
  • sun screens
  • self-cleaning glass
53
Q

Why are nano-scale titanium dioxide particles used in self-cleaning windows? (2)

A

They:
- catalyse breakdown of dirt in the presence of UV light
- cause water to spread out in a thin film, rather than forming droplets

54
Q

Are nano-scale particles/nanomaterials safe? (2)

A
  • nanomaterials currently used have been tested to ensure they cause no damage to individuals or the environment
  • the long-term effects are as yet, unknown
55
Q

What are the possible risks associated with use of nano scale particles of silver and titanium dioxide?

A

some people are concerned that nano scale silver (deodorants) and titanium dioxide (sun screens) are applied to the skin and can therefore be easily absorbed into the body.

56
Q

What are the 5 SMART materials you need to know about?

A
  • thermochromic pigments
  • photochromic pigments
  • polymer gels
  • shape memory alloys
  • shape memory polymers
57
Q

What is a SMART material?

A

A material whose properties change when a change occurs in their environment. This change is also reversible.

58
Q

How do thermochromic pigments change in response to their environment?

A

They change colour with changing temperature

59
Q

How do photochromic pigments change in response to their environment?

A

They change colour with changing light intensity

60
Q

How do polymer gels change in response to their environment?

A

They absorb/expel water and swell/shrink (up to 1000 times their volume) due to changes in pH or temperature.

61
Q

How do shape memory alloys change in response to their environment?

A

They regain original shape when heated

62
Q

How do shape memory polymers change in response to their environment?

A

They regain original shape when heated.

63
Q

Uses of thermochromic pigments? (2)

A
  • Baby thermometer
  • revealing images on mugs
64
Q

Uses of photochromic pigments? (1)

A
  • photochromic sunglasses
65
Q

Uses of polymer gels? (2)

A
  • nappies
  • artificial snow
66
Q

Uses of shape memory polymers? (2)

A
  • Car bumpers
  • Surgical structures
67
Q
A

GCSE Chemistry Unit 2 (2 decks)

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