A-level Physics (Advancing Physics)/Metals
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There are several physical properties of metals you need to know about:
Contents |
[edit] Electrical Conductivity
Metals consist of positive metal ions in a 'soup' or 'sea' of free (delocalized) electrons. This means that the electrons are free to move through the metal, conducting an electric current.
[edit] Stiffness
The charge between the negatively charged electrons and the positively charged ions holds the ions together, making metals stiff.
[edit] Ductility
Since there are no permanent bonds between the ions, they can move about and slide past each other. This makes metals ductile.
[edit] Toughness
Metals are tough for the same reason as they are ductile; they can slide past each other while still remaining together. So, instead of breaking apart, they change shape, resulting in increased toughness. This effect is called plasticity.
[edit] Elasticity
When a metal is stretched, it can return to its original shape because the sea of electrons which bonds the ions together can be stretched as well.
[edit] Brittle
The opposite of Elasticity; A material is likely to crack or shatter upon impact or force.
[edit] Questions
1. Would you expect a metal to have more or less conductivity than a semiconductor? Why?
2. How can the stress-strain graph for a metal be explained in terms of ions in a sea of electrons?
3. As a metal heats up, what happens to its conductivity? Why?
