Chemistry

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Name three examples of giant covalent structures
Diamond, graphite and silica
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Describe the structure of diamond
Each carbon atom is joined to 4 other carbon atoms
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Melting point of diamond?
High. 3500 degrees
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Does it conduct electricity
No, it doesn't contain any free electrons
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Appearance of a diamond
Transpant/crystalline
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Uses of a diamond
Gemstones, cutting glass and drill bits
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Structure of graphite
It is carbon where the carbon atoms form layers. Each carbon atom is joined to three other carbon atoms allowing the fourth to become a delocalised electron
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Does graphite conduct electricity
Yes, it contains delocalised electrons allowing it to conduct electricity
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How is graphite soft?
It allows the layers to slide over eachother and become malleable and ductile because there are no covalent bonds between them
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What is graphite used for?
Pencils and lubricant
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Where is silica found?
In sand
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What is it's structure similar to?
Diamond
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What is it's melting point like?
The structure is hard because of having no free electrons meaning that is has a high melting point
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What is different between a diamond and silica?
Diamond contains only carbon atoms, whereas, silica contains silicon and oxygen
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What else can carbon form?
Fullerenes
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What are fullerenes?
Cages and tubes with different numbers of carbon atoms
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Name the spherical fullerenes
Buckministerfullerene
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What is it used for?
Delivering drug systems into the body, found in lubricants and as a catalyst
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Name another fullerene
Nanotubes
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What are nanotubes useful for?
Reinforcing structures where lightness and strength is needed
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Do nanotubes conduct electricity?
Yes and they are used in semi-conductors
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What is the diameter of a nanotube?
Very small with diameter of 10,000 times less than a strand of human hair
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Strength of nanotubes:
Extremely strong with a very low density. Usually used in electronic circuits
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What are nano-tubes made from?
Graphene layers which are rolled into tubes
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What has graphene shown?
It is the strongest material ever tested and has the best electrical conductor
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Do the individual atoms have the same properties as bulk materials?
No this is demonstrated by diamond, graphite, carbon nanotubes and graphene all being from carbon atoms but not having the same properties
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What properties do smart materials have?
They are able to react to changes within the environment
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Name some examples of what they react to?
Temperature, light, pressure, pH and electricity
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The change is.....
Reversible and repeatable
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What is a shape memory alloy/polyamer?
A material that can be heated above a certain temperature so a material can return back to their original shape
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What can shape memory alloys be used for?
To start sprinklers in a fire alarm, controlling hot water valves and adjusting spectical frames
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Name two colour changing materials and how they work
Thermochratic materials change with temperature and photochromic materials change with light intensity
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What do polyamer gels do?
Absorbing/expelling water and swell/shrink due to changes in pH, temperature and concentration
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What are they used for?
Nappies, contact lenses and wound dressing
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What do electroluminescent materials do?
Give out light when an electrical current is applied to them
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Other cards in this set

Card 2

Front

Describe the structure of diamond

Back

Each carbon atom is joined to 4 other carbon atoms

Card 3

Front

Melting point of diamond?

Back

Preview of the front of card 3

Card 4

Front

Does it conduct electricity

Back

Preview of the front of card 4

Card 5

Front

Appearance of a diamond

Back

Preview of the front of card 5
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