Properties of Materials

0
587

Choosing the correct material for any particular task is essential for a manufacturing

activity.   Materials  are   divided   into:  Raw materials   (natural  and   artificial)   and

processed materials (artificial materials).  

Natural  materials  exist  in  nature,  and  we  use  them  as  they  are.  Examples  of  these

materials are wood, stone, sand, wool, etc. Natural resources are split into 3 categories:

animal, vegetable and mineral. In technical works, most of the materials are mineral and

often also vegetable  as in the case of wood. Every natural material has to be modified

for future use. For instance, wood has to be dried in order to remove the moisture. The

element iron has to be removed from the iron oxide mineral in a mineral oven and so

Thus, iron oxide or wood from a tree are raw materials that have to be converted

into elemental iron and wood pieces, which become processed materials. 

Processed materials can be obtained from other processed materials too. For example,

iron is used to get steel and steel is used to obtain stainless steel. But in all these objects,

where are the artificial objects? An artificial object is the one that has been created by

 

Properties of Materials

 Properties of materials can be divided mainly into physical and chemical properties. It’s

very important to define every property, including what the physical state (solid, liquid

or  gas)  of  a  material  is.  There  exists  a  fourth  state  that  is  not  very  common,  called

plasmatic state or plasma. All the properties defined in this lesson cannot be applied to

plasma.  

 

Extension activity: Find out further information about plasma, what its appearance is,

where it can be found, what differences exist     between plasma and the other physical

states, etc.  

Physical Properties

Density  refers  to  the  relation  between  the  mass  and  volume  of  a  solid.  Density  is

measured in Kg/m3, according to ISO units.

Dilation, contraction and Fusibility

Dilation: When material expands ( get bigger)due to heat

Contraction:  When material shrinks or contracts (gets smaller) due to heat 

Fusibility is the ability of a material to change into a liquid when heated to its melting

point. Examples of melting points

 

Iron melting point is 1535

Copper melting points 8083

 

 

Strength refers to the resistance of a solid to being bent, broken or having its form and

dimensions modified. To test the strength of a solid, try to deform it. Strength can be

studied under several conditions, such as the following: Compressive strength, tensile

strength,  Torque  or   torsion  and  Flexure  or   Bending.  According  to  the   degree  of

deformation,  solids  can  be  split  into  those  with  plastic  deformation  and  those  with

elastic  deformation.  In  the  first  case,  the  strength  is  enough  to  make  a  permanent

deformation.  Elastic  deformed  solids,  however,  return  to  their  original  forms  at  the

moment the forces being exerted are over.

 

Ductility is the ability of solid materials to be drawn out into wires. It typically occurs

in soft metals like copper, aluminum and tin.  

Malleability  is  the  ability  of  solid  materials  to  be  flattened  into  boards  and  plates.

Usually, ductility and malleability are properties found in the same kinds of materials.

 

Thermal and Electrical Conductivity: Both are the ability of heat or electricity to run

through the material, respectively.  In both cases, the materials can be good conductors

or  bad  conductors.  In  the  latter  case,  the  material  is  called  an  insulator.  Examples:

Copper is a good electrical and thermal conductor but polyethylene or Teflon is used as

an insulator.   

 

Optical properties

Optical properties describe how materials behave when light touches them. They can be

classified into:

a) Opaque: No light travels through them. e.g wood

b) Transparent: All light travels through them, and you can see what’s behind the

materials. e.g a glass window pane

c) Translucent: All light can travel through them but you cannot see what’s behind

them e.g frosted glass  

Sound Properties  

These properties refer to the ability of materials to conduct sound. Sound is a sort of

mechanical   vibration,    and   vibration    in   a    material   produces    transient   elastic

deformations. The behavior of a material in conducting sound depends on whether it’s

solid, liquid or gas because collisions between molecules are how sound is transmitted.  

Activity to think about: Could you speak on the moon?

 Chemical Properties

Oxidation: The change that occurs to most metals when in contact with oxygen

from air or water. Sometimes the oxidation becomes corrosion. 

Recyclability:  Materials  that  can  be  reused  to  make  new  ones  by  chemical

separation of their components are recyclable. Sometimes those materials that

are separated to be reused are simply used as fuel.

Toxicity: Materials which are harmful to the environment 

Biodegradability:    Materials    that    decompose    naturally    with   time    are

biodegradable. For example, an apple takes about 20 days to decompose, plastic

takes about 100 years, and glass takes about 400 years.  

LEAVE A REPLY

Please enter your comment!
Please enter your name here