Strength is the ability of a material to stand up to forces being applied without bending, breaking, shattering or deforming in any way. We often demonstrate the ‘strength’ of a material by performing a hand standing on a strong piece of timber (wood). It does not bend even under a certain weight. (see fig 8-1).

Elasticity is the ability of a material to absorb force and flex in different directions, returning to its original position. We often demonstrate the ‘elasticity’ of a material by springing up and down on a piece of steel rod (see fig 8-2).

Plasticity is the ability of a material to be changed in shape permanently. We often demonstrate the ‘plasticity’ of molten aluminum by pouring it into a mould. Once the aluminum has cooled down, it can be removed from the casting sand. It has a new shape.

Ductility is the ability of a material to change shape (deform) usually by stretching along its length. A person in fig 8-4 stretches the lead above his head. As it stretches it deforms (changes shape).

Toughness is a characteristic of a material that does not break or shatter when receiving a blow or under a sudden shock.

We demonstrate the ‘toughness’ of a material by hitting a piece or material to see if it will break or shatter. (See fig 8-5)

Hardness is the ability of a material to resist scratching, wearing and tearing and indentation. A person in fig 8-6 dressed in a kilt, slides along the floor to see if it will scratch. It will be considered to hard wearing if it resists scratching.