Materials The main substance from which all the things are made of, is called material. Materials can be natural: like wood, cotton or human made: like plastic. There are more than 3,00,000 types of materials available today, and the no. is still increasing as scientist are creating new materials. Main categories of materials are: wood, glass, metals, semiconductors, ceramic, polymers etc.
What are materials made of?All materials whether they are Solid, like steel or Liquid, like tea or Gaseous, like airare made up of atoms!
Atoms are what give materials their properties:Mass (kg) is to do with the number of atoms in a given volumeStrength is to do with how well atoms stick togetherCorrosion (rust) is to do with atoms reacting with each other
Atoms are made up of Protons, Neutrons and Electrons. At the centre of an atom (Nucleus), there will be Protons and Neutrons; Electrons move around the nucleus.- Protons carry positive charge, Electrons carry negative charge + and Neutrons are neutral. + + - Atoms overall are neutral Protons = Electrons -
Atoms stick together to make materials.How they stick together depends on what theelectrons doLots of metal Different atoms stickatoms share One kind of atom together, then thesetheir electrons gives electrons to groups stick together another kind of atom
Metal atoms stick together because the negative electrons attract the positive ions Metals have high melting points because these attractions are very strong Metals fuse with other metals to form “alloys”. All metals are solids at ordinary temperatures except Mercury. Most of the metals are found in combined form usually mixed with other elements and earthy materials. Metals conduct electricity because electrons can flow through the structure - this is in fact what electricity is!
Facts about Iron and SteelIron is available in nature in the form of minerals.These minerals are combination of iron, oxygen and sulfur.Iron is obtained from these minerals by following process:Minerals (iron + oxygen) + (Carbon) = iron + (Carbon + oxygen)Iron is an element, a pure substance which can rust on exposure towater and air.Steel is an alloy (a mixture) comprising of iron and carbon.Properties of iron and steel are different.Steel may not be as strong as iron is but it is more resistant anddoes not corrode and gets rusted like iron does. So steel is used forindustrial purpose more than iron.The iron that contains less than 2% of carbon is called steelwhereas which contain more than 2% of carbon is known as pig iron.
Iron and Steel CO2 Coke carbonIron Ore Cast iron Iron oxygen
Types of iron Mild Steel Stainless SteelCast Iron chromium nickel Medium Carbon Steel High Carbon Steel
Mild Steel: Contains 0-0.3% carbon Easy to shape Tough Most common and cheapest steel Best metal to weldMedium Carbon Steel:Contains 0.3-0.8% carbon More difficult to shape More brittle Harder and stronger than mild steelHigh Carbon Steel: Contains 0.8-2% carbon Very difficult to shape Most brittle Hardest and strongest steelStainless Steel: Iron with carbon, chromium and nickel atoms Stainless steel does not rust Because of its antibacterial properties, used in food transport/preparation and surgical equipment Comes in different grades of hardness Vs ductility depending on application More expensive
CarbonDiamond and graphite are examples of pure carbon. Both have different characteristics.Diamond is immensely strong. It is used for cutting strong material.Graphite is very soft (think of pencil). It is a good conductor of electricity. It is also used as a lubricant.Diamond Graphite
Carbon - oilCarbon forms chains which many different atoms can join to. All living matter,plants, animals, even human beings are based around carbon chains. Whenliving things die, they return to the earth. In some areas, over thousands ofyears, this material gets buried deep underground and heated and pressed.And then turns into oil. Oil is a finite resource. But our demand for it is never ending. Oil is getting expensive because it is extracted from difficult and less accessible places.
We will study about other materialslike Copper, Aluminium, Wood etc. in the next presentation : „Materials – Part II‟.