SC13 Transition Metals, Alloys and Corrosion ✓
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SC13a - Describe some typical chemical properties of transition metals.
• Usually form coloured compounds (colour decided by the ion involved e.g. copper forms blue compounds) • Chemical catalysts
SC13a - Describe some typical physical properties of transition metals.
• Malleable • Ductile • Lustrous (when polished) • Good conductors of heat and electricity • High melting points and densities (compared to groups 1 and 2)
SC13a - Where are Transition Metals found, on the periodic table?
In the middle of the periodic table, between groups 2 and 3
SC13b - How does sacrificial protection work?
• A more reactive metal is attached to Iron or Steel. • The oxygen and water are going to react with the more reactive metal instead, protecting the iron and steel
SC13b - What is corrosion?
When a metal continuously oxidises over time becoming weaker
SC13b - What is oxidation in terms of electrons and oxygen?
The loss of electrons and/or the gain of oxygen
SC13b - What is rusting?
The corrosion of Iron when it reacts with oxygen and water
SC13b - What makes a metal more or less reactive?
• How easily its able to lose its outer shell electrons (this is a combination of how many there are and how far away from the nucleus they are)
SC13b - Which metals are typically involved in sacrificial protection?
Zinc or magnesium, protecting iron or steel from rusting
SC13b - How can rusting be prevented?
• Keeping air away by storing the metal in an unreactive atmosphere of nitrogen or argon • Keeping water away, e.g using a desiccant powder that absorbs water vapour • Painting, coating with plastic, oiling and greasing
SC13c - For what two main reasons may a metal be electroplated?
• To improve its appearance • To improve its resistance to corrosion or rusting • save money as use less precious metal
SC13c - What is galvanising?
• Galvanising can be used to protect iron or steel objects. The object is coated in a layer of zinc, the zinc stops water and oxygen reaching the initial metal and stops corrosion
SC13c - What process is used to electroplate a metal?
Electrolysis
SC13c - When electroplating, what would you use as the anode and cathode?
• Cathode will be the object you are plating • Anode will be the metal you are plating it with. • Electrolyte contains ions of plating material, so they move to the object and are deposited as metal atoms, as they are replaced by ions leaving the anode
SC13c - Which two methods can be used to galvanise an object?
Dipping it in molten zinc or electroplating
SC13d - What is an alloy?
A mixture of a metal with one or more other (not necessarily metal) elements
SC13d - Why are alloys stronger than pure metals [4 marks]
• In a pure metal all the atoms are the same size in a regular structure • This allows layers to slide over each other easily • In an alloy, the atoms are different sizes in an irregular structure • This means layers cannot slide over each other as easily
SC13e - Name some uses of gold copper and aluminium linked to their properties that suit its use.
Gold: • Memory chips - Good conductor of electricity • Jewellery - Lustrous Copper: • Wires - Ductile • Coins - Cheap and malleable Aluminium: • Overhead cables - Low density
SC13e - Name some uses of magnalium, brass and nitinol linked to their properties that suit its use.
Magnalium (Magnesium and aluminium): • Lightweight mechanical parts • Low density • High strength Brass (Copper and zinc): • Plug in points • Corrosion resistant • Good conductor of electricity Nitinol (Nickel and Titanium): • Braces and glasses frames • Shape memory allows it to have 2 shapes depending on pressure or temperature.
SC13c - Why are some high end electrical connectors plated with gold?
• To improve their resistance to corrosion