2011 HL Section B question 4 (Thermal Equilibrium Diagram)

Question 1

Explain allotropy

Answer 1

the property of some chemical elements to take 2 or more different forms

Question 2

Explain interstitial solid solution

Answer 2

Parent metal atoms are bigger than atoms of alloying metal

smaller atoms fit into spaces between larger atoms

Question 3

difference between amorphous and crystalline structures

Answer 3

Amorphous structures have no pattern

crystalline structures have a pattern

Question 4

Discuss the degree of brittleness in body centered cubic structures (bcc) and the degree of brittleness in face centred cubic structures (fcc)

Answer 4

The bcc structure has an atom in the center and an atom in the corner of the cube which makes it brittle

in the the fcc structure the atoms are tightly packed, making it tougher

Question 5

Outline the various stages of solidification as a metal cools

Answer 5

As the metal reaches cooling point small particles cool first

solidification takes place in a pattern called dentrithic growth

each small particles grows to form a crystal or a grain

crystals grow together to form a solid