Metals

Question 1

Hardening

Answer 1

• steel 0.8% carbon, high carbon steel, heat to bright red (800°C)
• quench - (Rapid cooling) in salt water/oil
-steel is now hard but brittle this is needed for wear resistance of cutting tools

Question 2

Tempering

Answer 2

• heat to blue, purple, gold, straw
• quench in water
• this leaves most of the hardness but removes brittleness

Question 3

Carburising

Answer 3

• increasing carbon content of mild steel : 0.4% carbon
• get cheap steel, heat and soak it in a carbon rich powder to increase the carbon content, will have an increased carbon Layer around it. This is called case hardening and is cheaper than buying 0.8% carbon steel.

Question 4

What metals rust

Answer 4

Ferrous metals

Question 5

What 3 common ways protest steel from rust

Answer 5

Paint (hammerite), galvanising and electroplating

Question 6

What is galvanising

Answer 6

It is a process where steel is dipped into a bath of molten zinc

Question 7

What is the green oxide coating that forms on copper

Answer 7

Copper oxide / verdigris

Question 8

What property of mild steel makes it easy to sort from other metals during recycling

Answer 8

It’s magnetic

Question 9

Why is it considered essential to recycle aluminium

Answer 9

Because recycling aluminium saves more than 90% of the energy that would be needed to create a new piece.

Question 10

Why did copper replace lead as the material used to make water pipes

Answer 10

Lead compounds in water were toxic therefore contaminating the water so they were replaced by copper pipes which don’t react with water