Using Materials Flashcards

All 18 cards in this deck

What is corrosion?

The destruction of materials by chemical reactions with substances in the environment.
e.g. rusting of iron is an example of corrosion.

Which two substances must both be present for iron to rust?

Air (oxygen) and water.
If either is missing, the iron does not rust.

What are the steps to set up an experiment to show that both air and water are needed for rusting?
e.g. an iron nail in each of three boiling tubes

1. Tube 1: nail in air and water — rusts.
2. Tube 2: nail in boiled water with a layer of oil on top (no air) — no rust.
3. Tube 3: nail in dry air with a drying agent such as calcium chloride — no rust.

Name three barrier methods of preventing corrosion.

Greasing (oiling), painting and electroplating.
They stop air and water reaching the metal.

Why do aluminium objects not need protecting from corrosion?

Aluminium has an oxide coating that acts as a barrier, preventing contact between the metal and air/water.

What is sacrificial protection?
e.g. galvanising iron by coating it with zinc

Coating the metal with a more reactive metal, which corrodes instead of the metal underneath.
Zinc is more reactive than iron, so the zinc corrodes and the iron is protected.

Which metals are bronze and brass alloys of?

Bronze: copper and tin. Brass: copper and zinc.
e.g. bronze for statues and bells, brass for musical instruments and water taps.

What percentage of gold is in 24 carat gold and in 18 carat gold?

24 carat = 100% gold (pure); 18 carat = 75% gold.
Gold jewellery is usually an alloy of gold with silver, copper and zinc.

How do the properties of high carbon steel and low carbon steel differ?

High carbon steel is strong but brittle; low carbon steel is softer and more easily shaped.
e.g. high carbon steel for cutting tools, low carbon steel for car bodies.

True or false? Stainless steel rusts easily because it contains iron.

False. Stainless steels contain chromium and nickel, which make them hard and resistant to corrosion (e.g. cutlery).

What useful property do aluminium alloys have, and give a use.

They have a low density; used for aircraft bodies (also bicycle frames).

True or false? Two alloys made from the same two metals always have the same melting point.

False. Different proportions of the metals give different properties, including different melting points.

What is soda-lime glass made from, and what is borosilicate glass made from?

Soda-lime glass: sand, sodium carbonate and limestone heated together. Borosilicate glass: sand and boron trioxide, and it melts at a higher temperature than soda-lime glass.

What are the steps to make a clay ceramic?
e.g. a brick or a pottery plate

1. Shape the wet clay.
2. Heat it in a furnace (kiln) — this is called firing.

How can both low density (LD) and high density (HD) poly(ethene) be made from the same monomer, ethene?

By using different reaction conditions (different temperatures, pressures and catalysts).
HD poly(ethene) has unbranched chains that pack closer together, so it is denser.

What is the difference in structure between thermosoftening and thermosetting polymers?

Thermosoftening polymers are separate chains held by weak intermolecular forces, so they melt when heated; thermosetting polymers have cross-links between chains, so they do not melt.

What is a composite, and what are its two parts called?

A material made of two materials: a matrix (binder) surrounding and binding together fibres or fragments called the reinforcement.
e.g. carbon fibres (reinforcement) in polymer resin (matrix); also concrete and fibreglass.

True or false? Metals generally have higher melting points and conduct heat better than polymers.

True. That is why saucepans are made of metal but their handles are made of polymer.