Chemistry Study Notes: Chemistry in Everyday life

Chemistry Study Notes: Chemistry in Everyday life

Synthetic Materials
The materials created by man using the natural materials, are known as synthetic materials.

  • It was discovered by an English Mason, Joseph Aspdin in 1824. He called it Portland cement because he thought that it resembled the limestone found in Portland.
  • Approximate Composition of Portland cement
                       Calcium oxide (CaO) 60-70%
                       Silica (SiO_2)                 20-25%
                       Alumina (AI_2 O_3 ) 5-10%
                       Ferric oxide (Fe_2 O_3 ) 2-3%
  • Raw materials are limestone (provides lime), clay (provides alumina and silica), gypsum (reduces the setting time of cement).
  • When water is mixed with cement and left as such for sometime, it becomes a hard mass. This is know as setting of cement. It is an exothermic process, therefore cement structures have to be cooled upto 7 days by sprinkling water.
  • Mortar is a mixture of cement, sand and water. It is used for plastering walls and binding bricks and stones.
  • Concrete is a mixtures of cement, sand, gravel or small pieces of stone and water. It is used for the construction of floors.
  • The structure having iron rods embedded in wet concrete, is known as reinforced concrete. 

Glass (Na_2 O.CaO.6SiO_2)

  • It is a supercooled liquid of silicates.
  • Raw material used for the formation of glass are sodium carbonate, calcium carbonate and sand.
  • Finely powdered mixture known as batch, is mixed with cullet (broken glass pieces) and then fused in a tank furnace at 1673 K. After few hours, molten glass is obtained.
  • Molten glass is cooled slowly and uniformly. The process of slow and uniform cooling is known as Annealing
  • Different addition may produce different coloured glasses.

Variety of glass and Uses
  • Soft glass - It is a mixture of sodium or calcium silicates. It is used in making window glass, mirrors and common glass wares etc.
  • Hard glass - It is a mixture of potassium and calcium silicates. It is more resistant to the action of acids for making hard glass apparatus.
  • Flint glass - It is mainly a mixture of sodium, potassium and lead silicates. It is used in making bulbs and optical instruments.
  • Pyrex glass (Borosilicate glass) - It is used in making pharmaceutical containers, lab apparatus and over ware.
  • Quartz glass (Silica glass) - It is used in the preparation of chemical apparatus and optical instrument.
  • Crookes glass - It is used for making lenses for spectacles.
  • Photochromatic glass - On exposure to bright light, photochromatic glass darkens temporarily. So, it is very useful as a Sun shield.
  • Safety glass - The three layers are joined together by the action of heat and pressure. It does not break easily under impact and is used in auto vehicle wind shield.
  • Optical glass - It is used for making lenses for microscope, telescope and spectacles.
  • Glass fibres - used as insulating material in oven, refrigerator etc.
  • Optical fibres - are extensively used in telecommunication surgical operations etc. Optical fibres can transmit images round corners. 
  • Lead crystal glass - Lead glass has a high refractive index. So, it is used for making expensive glass ware.
  • Etching of glass - Glass is attacked by hydrofluoric acid (HF), therefore it is used in the etching of glass.

1 comment: