SAC 1 Revision Flashcards
What is an Alloy
An alloy is when a metal and other substances are melted, mixed and cooled to form an alloy which creates a material with specific properties.
properties of alloys
Harder than pure metal and lower melting point.
What is annealing
Where metal is heated to a moderate temperature and allowed to cool slowly. The metal becomes softer with improved ductility. Large crystals form.
What is quenching
Where metal is heated to moderate temperature and cooled quickly. The metal is harder and brittle. Tiny crystals form.
What is tempering
Metal is quenched then heated at a lower temperature than it was quenched then allowed to cool. Metal becomes hard but less brittle. Intermediate size crystals form.
Properties of metals
They are high densities, good conductors of heat, good conductor of electricity and have a high melting point.
Properties of ionic compounds
Don’t conduct electricity in a solid state. High melting point, hard and brittle, generally soluble in water.
Properties on on non metallic substances
Low melting point, non-conductor of electricity, malleable, soluble in solvents.
Nobel Gases
are stable because they have a full valance electron shell.
Metallic bonding model
Cation (positive ions) Lattice held together by a sea of delocalized electrons
Difference between covalent and ionic bonding
Ionic bonding involves the transferring of electrons between a metal and non-metal while covalent bonding involves the sharing of electrons between 2 non-metals.
Benefits of alloys
Improved strength, Resistance to corrosion, Less malleable and reduced melting temperature.
What are substitutional alloys
The atoms of the element added replace some of the cations.
What are interstitial alloys
A small proportion of an element within significantly smaller atoms is added to a metal.
