C6.1 - Materials Flashcards by Rhea Rhea

Ceramics

Hard, non-metallic materials

Eg. Brick, china, porcelain, glass

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Structure of ceramics

Contain metals & non-metals

Combined to form giant ionic lattices / giant covalent structures

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Typical properties of ceramics due to their structure

high melting point
hard & stiff, but brittle
poor conducts of electricity / heat
unreactive (compounds are mostly oxides)

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How is glass made?

What is its structure?

Melting sand
Allowing it to cool & solidify

= irregular giant structure without crystals, usually transparent

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How are other ceramics (not glass) made

Heating clay to very high temps

Tiny crystals form, joined together by glass

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Why is china & porcelain coated in a glaze & reheated

To form a 
- smooth
- hard
- waterproof 
Surface

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Why is aluminium a good material (metal) for overhead electricity cables

good conductor of electricity
strong enough (doesn’t stretch / snap easily)
not too dense (lightweight)
corrosion resistant

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Compressive strength

Measure of how strong a material is when squashed

Low = squash easily

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Tensile strength

Measure of how strong a material is when stretched

Low = snap easily when stretched

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Why is porcelain a good material for insulators where cables are fixed on top of a structure (to stop current passing from cable to pylon)

high compressive strength
high electrical resistance (poor conductor of electricity)
but low tensile strength

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why would poly(propene) not be good for cable insulators

low tensile strength
low compressive strength
but poor conductor of electricity

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Composite material

Material made from 2 or more different materials, with different properties to those of the materials

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List composite materials

polyester-cotton
fibreglass
carbon fibre
concrete
steel-reinforced concrete
plywood

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How is polyester-cotton made

Weaving cotton thread with polyester fibre (artificial polymer)

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What properties does polyester-cotton have that make it good for clothes?
(Different from properties of polyester & cotton)

comfortable
hard-wearing
easy to wash & dry

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Resin

Substance that changes from liquid state to solid state because of chemical reactions

How are many composite materials made

Fibres embedded in a polymer resin

What are the properties of fibre & resin

Fibre

low density
high tensile strength

Resin

hardwearing
not strong

Properties of composite material made from resin & fibres

Examples of this composite material:

lightweight
strong
hard

Eg.

fibreglass (canoes, boats, surfboards)
carbon fibre (sports equipment, aircraft, cars)

Concrete

Composite material made from

aggregate (small stones)
sand
cement
water

Properties of concrete

Properties of steel

Concrete

high compressive strength
low tensile strength

Steel
- high tensile strength

Properties of steel-reinforced concrete

Embedding steel rods in concrete

high compressive strength (useful for foundations)

- high tensile strength (can carry heavy loads)

How is wood made and why is this a problem

long fibres lying side-by-side = grain

- stronger along grain than across grain

What is plywood

Why is it better than wood

Composite material
Thin sheets of wood glued together in layer
Grains in each layer at right angles to layer below

= resists bending in both directions (useful for floors/walls)

Pros & cons of using Poly(ethene) for hot drink plastic cups

+ cheapest - maximum usable temp too low, cant hold boiling water - low tensile strength

Pros & cons of using PET for hot drink plastic cup

+ highest tensile strength + highest melting point - maximum usable temp too low = can’t hold boiling water - most expensive

Pros of using poly(propene) for hot drink plastic cups | Why is it the best plastic

+ moderate tensile strength + high melting point + high maximum usable temp(>100ºC) = can hold boiling water

Life-cycle assessment (LCA)

Analysis of the impact of making, using & disposing of a manufactured product

An LCA should include data about:

- sustainability (use of raw material & energy) - environmental impact (waste products & pollution) - lifespan of product - if material can be recycled - disposal (how easily material decomposes)

Recycling

Processing a used material / object so its substances can be reused

Why is recycling important

- conserves limited raw materials & energy resources - reduces release of harmful substances into environment - reduces waste

What factors determine if a material should be recycled

- how easily waste can be collected & sorted - amount & type of by-products released by recycling - cost of recycling compared to disposal in landfill / incineration (burning) - amount of energy involved at each stage

How are materials recycled

- materials sorted - materials checked (contamination) - sorted waste shredded / crushed into smaller pieces - waste processed

How is metal processed during recycling

Melted by heating | Molten metal poured into moulds to produce new blocks (ingots)

How is paper processed during recycling

Mixed with water Cleaned Rolled & heated to make new paper

How is glass processed during recycling

Melted by heating | Moulded into new glass objects

How are polymers processed during recycling

Melted Formed into new objects Eg. - PET - poly(ethene) - poly(propene)