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Koky chem > SC26 - Bulk and Surface Properties of Matter Including Nanoparticles > Flashcards

SC26 - Bulk and Surface Properties of Matter Including Nanoparticles Flashcards

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1
Q

SC26a - What are ceramics?

A

A range of durable compounds that change very little when heated

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2
Q

SC26a - What are the properties of ceramics?

A
  • Chemically unreactive hard and stiff brittle
  • Poor electrical and thermal conductors
  • High melting points

These properties are due to their giant ionic/covalent structures with strong bonds

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3
Q

SC26a - What are three examples of clay ceramics?

A
  • Bricks
  • Porcelain
  • China
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4
Q

SC26a - How are clay ceramics created?

A
  • When clay is heated to high temperatures, tiny crystals form and join together.
  • Bricks are decorated by adding a coloured substance before heating, or by moulding in patterns.
  • Porcelain and china are dipped into a ‘glaze’ and heated strongly.
  • This makes them hard, waterproof and smooth.
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5
Q

SC26a - How is glass created?

A

Melting sand and then allowing it to cool and then solidify

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6
Q

SC26a - What are the similarities and differences between glass and clay ceramics?

A
  • They both have similar properties because they both have giant structures
  • But, the atoms in glass aren’t arranged in a regular pattern to form crystals and so glass is transparent rather than opaque
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7
Q

SC26a - How is modern window glass created?

A

The float process:

  • Molten glass is poured onto a bath of molten tin.
  • As it spreads out, it is drawn away and cooled in a continuous process
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8
Q

SC26a - What are polymers?

A

Polymers are substances with high relative formula masses as they are formed by joining many monomers (smaller molecules) together

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9
Q

SC26a - What are some general properties of polymers?

A

Properties depend on structure and chemical composition, but generally:

  • Can be moulded into complex shapes
  • Strong
  • Chemically unreactive
  • Poor electrical and thermal conductors
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10
Q

SC26a - How can PVC be made softer?

A

By using plasticisers in its manufacturing.

This makes it more flexible

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11
Q

SC26a - What are some properties of metals?

A
  • Strong
  • Hard
  • Shiny
  • High melting points
  • Good electrical and thermal conductors
  • Malleable
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12
Q

SC26a - How can metals be made stronger?

A

Alloying: Mixing the metal with one or more other elements

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13
Q

SC26a - Why may a metal be electroplated?

A
  • To improve resistance to corrosion
  • To improve appearance
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14
Q

SC26b - What is a composite material?

A

A material that is made up of two or more materials, combined to make a material with improved properties

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15
Q

SC26b - How do the individual materials in a composite material relate to each other?

A
  • They often have contrasting properties
  • They can be separated out by physical means
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16
Q

SC26b - What are the reinforcement and the matrix?

A
  • The reinforcement is what you are binding together
  • The matrix is how you hold them together

(reinforcement is straw and matrix is the glue)

17
Q

SC26b - What is the difference between tensile and compressive strength?

A
  • Tensile: Resistance when stretched
  • Compressive: Resistance when squashed
18
Q

SC26b - What is wood a composite material of?

A

Cellulose fibres in a matrix of a polymer called lignin

19
Q

SC26b - How does the strength of wood differ depending on how you cut it?

A

It is stronger along the grains (parallel to lines of lignin) than across the grain (perpendicular to lines of lignin)

20
Q

SC26b - How is plywood strong from all angles?

A

It has an odd number of sheets of wood glued in right angles to the sheet below so that you are always cutting across and along the grain simultaneously

21
Q

SC26b - What is pykrite a composite of?

A

Reinforcement of ice in a matrix of wood pulp

22
Q

SC26b - What is concrete a composite of?

A

Reinforcement of sand and aggregate (small stones/gravel) in a matrix of cement (and water to help it set)

23
Q

SC26b - What is fibreglass a composite of, and why is it useful?

A
  • Reinforcement of thin glass in a matrix of resin polymer.
  • Glass fibres are brittle but with low density and high tensile strength
  • Resin is hardwearing but not strong.
  • Combining them makes fibreglass low density, strong and hardwearing
24
Q

SC26b - Why may concrete be ​reinforced with steel?

A
  • Concrete has a low tensile strength but high compressive strength
  • Steel is very dense and more expensive than concrete
  • Reinforced with steel it will have high tensile and compressive strength and also be cheaper and less dense than steel alone
25
Q

SC26c - What are bulk materials (give examples)

A

Materials consisting of a large number of atoms e.g:

Lumps and powder

26
Q

SC26c - What are nanoparticles?

A

Particles consisting of just a few hundred atoms

27
Q

SC26c - Compare the size of a nanoparticle to that of an atom and that of a cell

A

Atom: 0.1nm

Nanoparticle: 1-100nm

Bacterium cell: 1000nm

28
Q

SC26c - How are nanoparticles formed?

A

They largely occur naturally, but can be formed through manufacturing processes

29
Q

SC26c - What does it mean if a substance is nanoparticulate?

A

It consists of nanoparticles

30
Q

SC26c - What properties of nanoparticles make them useful?

A
  • Their small size
  • Their large Surface area : Volume ratio
31
Q

SC26c - What is nanoparticulate titanium dioxide used for and why?

A
  • It is used for (almost invisible) sunscreen
  • Titanium dioxide absorbs harmful UV radiation
  • When nanoparticulate, it is small enough to be transparent
32
Q

SC26c - How do stain resistant clothes work?

A
  • Nanoparticles on the clothes fibres have a really large Surface area : Volume ratio
  • This makes them useful as chemical catalysts
  • They catalyse the breakdown of stains, cleaning the clothes
33
Q

SC26c - What are the dangers of nanoparticles?

A
  • Their small size allows them to be breathed in or passed through cell-surface membranes
  • Their large SA:V allows them to catalyse harmful reactions and carry toxic substances
34
Q

SC26c - Why are the risks of nanoparticles not fully known?

A

Nanoparticulate materials haven’t been in use for very long

Koky chem (24 decks)

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