5 1 transition metals alloys and corrosion

Transition metals are located in the middle of the Periodic Table.

Properties of transition metals include:

A main use of transition metals is as catalysts.

The catalyst used in the Haber process is iron.

False. Transition metals form coloured compounds.

Corrosion is the destruction of materials by chemical substances in the environment which act on them over a period of time.

Rusting specifically refer to the corrosion of iron.

The word equation for the rusting of iron is: iron + water + oxygen ⟶ hydrated iron(III)oxide

Two conditions needed for rusting of iron to occur are water and oxygen.

Examples of barrier methods that can prevent rusting are:

Nail A will rust because it is exposed to oxygen AND water.

False. Galvanising is the method of coating iron with a layer of zinc.

Sacrificial protection is when a more reactive metal is intentionally allowed to corrode to protect the metal it is covering.

Zinc is used to protect iron from corrosion because it is more reactive than iron so will react more readily with oxygen.

Electroplating is process of coating the surface of one metal with a layer of a different metal.

False. In electroplating, the cathode is made from the object to be electroplated.

Uses of electroplating include:

The anode is the copper rod as the anode is the metal you are using the coat the other metal with.

At the anode, nickel atoms lose electrons to positive ions and move into the solution. They are attracted to the cathode (negative electrode) where they gain electrons to form nickel atoms which coats the spoon.

An alloy is a mixture of metals, where the metals are mixed together physically but are not chemically combined.

True. Alloys can also be made from metals mixed with non-metals such as carbon.

Alloys contain atoms of different sizes which distort the regular arrangement of atoms.

The increased hardness and strength of an alloy is caused by the different size atoms which distort the regular arrangements of atoms, preventing the layers from sliding over each other easily.

Advantages of using alloys over pure metals are:

False. Alloys are physical mixtures of metals, where the metals are not chemically combined.

Alloys often have greater strength / hardness, or resistance to corrosion / extreme temperatures compared to pure metals.

Uses of stainless steel include:

Mild steel can be used to make car bodies because it is soft and malleable.

The two main elements in steel alloys are iron and carbon.

Iron from a blast furnace is not that useful because it is too brittle.

The metal used to make food cans because it is non-toxic and resistant to corrosion / acidic food stuff is aluminium.

False. Aluminium is used for making aircraft and electrical wires (overhead cables).
Copper is used for water pipes.

Aluminium is a better choice than copper for overhead electrical cables because it is:

Copper is used for electrical wiring because it is a good conductor of electricity and ductile.

Aluminium and copper are used to make saucepans because they are:

The property of copper that means it can be shaped into saucepans is malleability.

True. Gold alloys are used to make jewellery.

Pure gold cannot be used to make jewellery because it is too soft and malleable.

False. Brass is an alloy of copper and zinc.

Two uses of brass are in plumbing and carpentry.