using the earths resources 2

Life Cycle Assessments

used to assess the impact on the environment of getting and processing raw materials, making the product (and packaging), using and maintaining the product, and disposing of the product

Total energy in LCAs

The total energy needed to extract the material, make and distribute the product, and any transport are all counted

How LCAs are carried out

Listing all energy and material inputs and outputs into the environment, assessing the impact of these on the environment, and interpreting results to help decide on materials, processes, products or services

What LCAs provide

An estimate of the environmental impact of all the stages of a product’s life cycle

Limitations of LCAs

LCAs require subjective judgements of environmental impact so the results are often uncertain

Reducing use of resources

Reducing use, reusing and recycling materials reduces the use of limited resources, as well as energy, waste and environmental impacts

Conditions for rust

Rust can only occur when both air and water are present

Rust experiment

Iron is put into test tubes with only air, only water, and both present to show rusting conditions

Preventing corrosion

Using barriers like greasing, paint or electroplating

Sacrificial protection

Placing a more reactive metal on top so it reacts instead of the iron

Why alloys are harder

Alloys are harder than pure metals because they contain ions of different sizes

Bronze

Alloy of copper and tin, used to make statues and decorative items

Brass

Alloy of copper and zinc, used for musical instruments and hardware of taps

Gold alloys

Mixed with different metals like copper or silver so it doesn’t wear as easily, used in jewellery

Steel

Alloy of iron, carbon and other elements with controlled amounts to give different properties

Carbon steels

Cheap steels used for machinery and car bodies

High carbon steel

Strong and brittle

Low carbon steel

Soft and easily shaped

Chromium-nickel steels

Hard and resistant to corrosion, often used for cooking utensils (stainless steel)

Aluminium alloys

Low density and often used for military vehicles

Composite definition

Enhanced material made of reinforcement and matrix (which binds reinforcement)

Thermosoftening polymers

Melt when heated, low density (LD), made in high pressure and trace oxygen, polymer chains randomly branched, cannot pack closely together

Thermosetting polymers

Do not melt when heated, high density (HD), made with catalyst at 50°C and slightly raised pressure, straighter polymer chains, can pack closely together, stronger than LD polyethylene

Poly(ethene) production

Both LD and HD poly(ethene) are produced from the same monomer ethene

Borosilicate glass

Made from sand and boron trioxide, has a higher melting point

Soda-lime glass

Made by heating sand, sodium carbonate and limestone, more common