Metals, Alloys and Corrosion (1)
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What are transition metals?
the central block of metals in the middle of the periodic table
What are the properties of transition metals? (8)
• hard • strong • shiny • malleable • conduct heat and electricity well • high melting points (with the exeption of mercury) • high densities • colourful (when in a compound) (boldened properties are not the same as typical properties of metals)
What are some uses of copper? and why is it used for these purposes? (2)
• Water pipes - it is malleable and corrosion resistant • Electrical wires - it is a good electrical conductor
What is a general use of all transition metals?
catalysts
Why are alloys stronger and harder than pure metals?
Pure metals have a regular arrangement of identical ions so layers can slide over each other and are malleable. As different elements have different sized atoms, adding an element will disrupt the layers of pure atoms, making it more difficult for them to slide over each other.
What are some specific properties of iron? and why is this important?
• soft • easily shaped this makes it too bendy for most uses
What elements are added to iron to make low-carbon steel? what are the properties of this alloy? (1) and what is it used for? (1)
(iron) + carbon 0.1-0.3% it is easily shaped it is used for car bodies
What elements are added to iron to make high-carbon steel? what are the properties of this alloy? (3) and what is it used for? (2)
(iron) + carbon 0.22-2.5% it is very strong, inflexible and brittle it is used for blades for cutting tools and bridges
What elements are added to iron to make stainless steel? what are the properties of this alloy? (2) and what is it used for? (2)
(iron) + carbon + chromium + nickel (sometimes) it is corrosion-resistant and hard it is used for cutlery and containers for corrosive substances
What are some uses of steel? (8)
• bridges • engine parts • cutlery • washing machines • pans • ships • tools • cars
What are some common alloys? (5)
• steel • brass • bronze • gold alloy • magnalium
Tell me about brass. and give two uses. • materials? • appearance? • malleability?
• an alloy of copper and zinc • gold-like appearance • quite malleable it is often used in water taps and door fittings
Tell me about gold alloys. and give a use. • materials? • hardness?
• an alloy of gold and a combination of zinc, copper and silver • hard it is used to make jewellery
Tell me about magnalium. and give two uses. • materials? • strength? • relative weight? • corrosion resistance?
• an alloy of aluminium and magnesium • strong • lightweight • corrodes less easily than pure aluminium it is used to make parts of an aeroplane and fireworks
Define corrosion.
the reaction of metals with the oxygen and water in their environment
What is the general equation for corrosion.
metal + water + oxygen -> hydrated metal oxide
What are the two main ways of preventing corrosion?
• Creating a barrier • Sacrifical method
How does creating a barrier work to prevent corrosion? and what are a few different ways of doing this? (4)
it keeps oxygen, water or both away from the metal to prevent corrosion • painting the metal • coating the metal in plastic • electroplating • oiling or greasing
What is electroplating? and how does this work?
A process that uses electrolysis to coat the surface of one metal with another metal. The cathode is the object that is going to be electroplated and the anode is a bar of the metal that will end up coating the surface of the object. The electrolyte is a solution containing the metal ions of the metal that is being plated on the object.
What are two uses of electroplating?
• Coating cutlery and cooking utensils for protection. • Improving the appearance of jewellery by coating it with a metal like gold or silver.
What is sacrificial protection of corrosion? and how does it work?
this involves placing a more reactive metal with the metal the water and oxygen react with this ‘sacrificial’ metal instead of the other metal in the object you’re protecting