Transition Metals, Alloys & Corrosion Flashcards
All 24 cards in this deck
Where are the transition metals found in the periodic table?
In the central block, between Group 2 and Group 3.
State four typical properties of transition metals.
High melting point, high density, they form coloured compounds, and the metals and their compounds show catalytic activity.
True or false? Most of the metals in the periodic table are transition metals.
True. The transition metals form the large central block of the table.
True or false? The compounds of transition metals are usually colourless.
False. Transition metal compounds are typically coloured, e.g. iron(III) chloride is coloured.
How do the typical properties of Group 1 metals differ from those of transition metals?
Group 1 metals have lower melting points and lower densities, form white/colourless compounds and are not used as catalysts.
In terms of its position in the periodic table, why would you expect platinum to act as a catalyst?
Platinum is a transition metal, and catalytic activity is a typical property of transition metals.
What happens to a metal when it corrodes?
The metal is oxidised (it reacts with oxygen to form an oxide).
True or false? Iron will rust if it is left in completely dry air.
False. Both oxygen (air) and water are needed for iron to rust.
Name three barrier methods used to prevent iron rusting, and say how a barrier works.
Painting, oiling/greasing and coating with plastic; the barrier excludes oxygen and water from the iron surface.
How does sacrificial protection stop iron from rusting?
e.g. iron galvanised with a layer of zinc
A more reactive metal is oxidised in preference to the iron; the zinc corrodes instead of the iron because zinc is more reactive than iron.
Give two reasons why a metal object is electroplated with gold.
To improve its appearance and to increase its resistance to corrosion.
What are the steps to set up the electroplating of a metal object?
e.g. plating a steel spoon with silver
- Object = negative electrode (cathode): the steel spoon.
- Plating metal = positive electrode (anode): silver.
- Electrolyte = solution of a salt of the plating metal: silver nitrate solution.
What is an alloy?
A mixture of a metal with one or more other elements.
Using a model of layers of atoms, why is an alloy usually stronger and harder than the pure metal?
e.g. brass compared with pure copper
The alloy contains atoms of different sizes, which disrupt the layers so they cannot easily slide over each other; zinc atoms are larger than copper atoms, so brass is harder than pure copper.
True or false? In a pure metal the layers of atoms can easily slide over each other.
True. All the atoms are the same size, so the regular layers slip easily, making pure metals softer.
True or false? An alloy is a compound formed when two metals react together.
False. An alloy is a mixture, not a compound.
Why is iron alloyed with other metals to make alloy steels?
Pure iron is too soft and corrodes easily; alloy steels are harder, stronger and can be made more resistant to corrosion.
Which metal is added to iron to make stainless steel, and what is stainless steel used for?
Chromium (often with nickel); it resists corrosion, so it is used for cutlery, sinks and chemical plant.
Which properties of aluminium make it suitable for aircraft bodies and overhead power cables?
Low density, resistant to corrosion, and a good conductor of electricity (and its alloys are strong).
Which properties of copper make it suitable for electrical wiring and water pipes?
It is a very good conductor of electricity, ductile, and unreactive with water.
Which properties of gold make it suitable for jewellery and electrical contacts?
It is very unreactive so does not corrode or tarnish, it is shiny, and it conducts electricity well.
Which metals make up brass, and give one use of brass.
Copper and zinc; used for taps, door fittings and musical instruments because it is harder than pure copper.
Which metals make up magnalium, and why is it useful?
Aluminium and magnesium; it has a low density but is stronger than pure aluminium, so it is used in aircraft parts.
Which properties would you look for in a data table when choosing a metal for an aircraft body?
Low density, high strength and good resistance to corrosion.