Material Properties

Question 1

malleability

Answer 1

the ability of a material to withstand deformation by compression (before it shows sign of cracking) e.g copper — malleability increases with temp. and therefore metals which need to be bent, rolled or extruded, are heated first

Question 2

ductility

Answer 2

the ability of a material to be drawn out, can be deformed under tensile stress, (ability to be stretched into a wire) e.g copper`

Question 3

toughness

Answer 3

the ability of a material to withstand sudden impact without fracture (can also refer to withstanding bending), opposite to brittle

Question 4

elasticity

Answer 4

the ability of a material to flex and bend when forces are applied and to regain normal shape and size when those forces are removed

Question 5

plasticity

Answer 5

the ability of a material to be permanently changed in shape by external forces e.g hammer blows, pressure, without cracking, metals and thermoplastic polymers tend to generally be more plastic when heated

Question 6

hardness

Answer 6

the ability of a material to resist abrasive wear, indentation or formation, important property of cutting tools e.g drills

Question 7

durability

Answer 7

the ability of a material to withstand wear and teach, weathering and the deterioration or corrosion this may cause, weathering can results in mechanical weakening

Question 8

stability

Answer 8

the ability of a material to resist changes in size and shape due to its environment, e.g timber tends to warp and rot due to changes in humidity, metals and some plastics deform subject to continual stress: these processes are known as ‘creep’

Question 9

strength

Answer 9

the ability of a material to withstand force without breaking or permanently bending

Question 10

tensile strength

Answer 10

the ability of a material to resit stretching or pulling forces

Question 11

compressive strength

Answer 11

the ability of a material to withstand pushing forces which attempt to crush or shorten the material

Question 12

bending strength

Answer 12

the ability of a material to withstand forces with attempt to bend the material

Question 13

shear strength

Answer 13

the ability of a material to resist sliding forces acting against each other

Question 14

torsional strength

Answer 14

the ability of a material to withstand twisting forces under torsion or torque

Question 15

magnetism

Answer 15

a property possessed by many elements, and is the product of the orientation of electrons about their atoms, only a few elements are strongly magnetic

Question 16

fusibility

Answer 16

the ability of a material to change into a molten or liquid state when heated to a certain temperature, i.e melting point, varies between materials but is essential to processes such as casting welding and soldering

Question 17

density

Answer 17

defined as mass per unit volume — relative density is the ratio of the density of the substance to that of pure water at a temperature of 4 degrees celsius

Question 18

electrical conductivity

Answer 18

all materials resist the flow of electricity to some extent - conductors offer a very low resistance to the flow of an electric current, e.g metals like copper, silver and gold

Question 19

electrical insulators

Answer 19

offer a high resistance to the flow of electricity — non-metals are generally good insulators but vary individually e.g ceramics, glass, nylon, PVC

Question 20

semi-conductors

Answer 20

slowed electric current to flow under certain conditions, e.g silicon and germanium in their pure state are poor conductors, but their electrical resistance can be altered by the addition of impurities

Question 21

meaning of thermal properties

Answer 21

the way in which a material reacts to heat

Question 22

thermal conductivity

Answer 22

relates to how heat travels through the material, measured in watts per metre per degree Celsius, copper + aluminium have high thermal conductivity

Question 23

thermal insulators

Answer 23

relates to materials with low value thermal conductivity, generally non-metals — used to prevent heat gains and losses e.g pan handles, loft insulation

Question 24

thermal expansion

Answer 24

materials generally expand when they get hot and shrink upon cooling, control mechanisms also used this effect e.g car thermostats, automatic kettles

Question 25

meaning of optical properties

Answer 25

refers to how materials react to light and heat by reflection, radiation and absorption

Question 26

opaque

Answer 26

does not allow light to pass through e.g house brick

Question 27

translucent

Answer 27

allows some light to pass through e.g photocopy paper

Question 28

transparent

Answer 28

allows light to pass through e.g glass