Metals Flashcards
(2 cards)
Why are alloys stronger and harder than pure metals?
The atoms of the elements added to the pure metal in the alloy have a different size than the atoms of the metal, and these atoms of the added elements disrupt the orderly layered arrangement of the metal atoms. This causes layers of metal atoms to be unable to slide past one another, causing alloys to be stronger and harder than pure metals.
Zinc is used to make galvanised iron and galvanised steel which protects the iron or steel object from rusting. Why is zinc a more suitable choice than copper to prevent iron from rusting?
Zinc is more reactive than iron while copper is less reactive than iron. If the outer layer/coating of zinc around the iron is scratched off, zinc can still prevent iron from rusting as it will corrode preferentially in place of iron and act as a sacrificial metal. (zinc transfers electrons to iron as it is more reactive).
However, since copper is less reactive than iron, if the outer layer of copper is scratched off and the iron is exposed, the copper will not corrode preferentially in place of iron and this causes the iron to rust as it is exposed to oxygen and water.
