CHEMISTRY GROUP 5 CHAPTER 9.5 [Glass And Ceramics]
Glass ~ Glass is made from sand. ~ Glass is normally referred to a transparent , shiny substance that breaks rather easily. ~ Evidence has shown that glass has been used for more than 3000 years ago. ~ The major component of glass is silica or silicon dioxide , SiO 2 . ~ Glass can be made by heating a mixture of silicon dioxide and metal carbonates to a temperature above 1500 c .
Type And Uses Of Glass <ul><li>4 types of glass that are commonly used namely fused glass , soda-line glass , borosilicate glass and lead crystal glass. </li></ul>
Fused Glass ~The simplest type of glass is fused glass. It consists mainly of silica. ~Fused glass is made by heating silica to a molten liquid. The liquid is then cooled rapidly to form an amorphous solid. ~During fast cooling , the SiO 4 tetrahedras do not have time to crystallise out to form a highly regular structure. Thus, the structure resembles that of a liquid state. Hence, glass is a super-cooled glass. ~Fused glass is expensive because exceptionally high temperature must be maintained during its manufacturing.
Soda-lime glass ~Soda-lime glass is the most common and earliest used glass. ~It is made by heating sand (silica) with limestone (CaCO 3 ) and sodium carbonate (Na 2 CO 3 ) at around 1500 c and cooling it quickly. ~Soda-lime glass is a mixture of sodium silicate and calcium silicate. The presence of sodium silicate makes the glass melts at a lower temperature.
Borosilicate glass <ul><li>When boron oxide, B 2 O 3 is added to soda-lime glass, borosilicate glass is formed. </li></ul><ul><li>Borosilicate glass has a lower thermal expansion coefficient. </li></ul><ul><li>It is about 3 times as heat-resistant as soda-lime glass. </li></ul><ul><li>It is also more resistant to chemical </li></ul>
Lead Crystal Glass <ul><li>Lead crystal glass is normally called crystal or lead glass, PbO for calcium oxide , CaO and often for part of the silica, SiO 2 used in soda-lime glass. </li></ul><ul><li>Lead crystal glass is soft and easy to melt. </li></ul><ul><li>It is more expensive than soda-lime glass. </li></ul><ul><li>Lead crystal glass is used for the finest tableware, lead crystal glassware and art objects. </li></ul><ul><li>Lead crystal glass is suitable for fine crystal because it is optically transparent and contain much more lead. </li></ul>
Ceramics <ul><li>Pieces of broken ceramics from more than 6000 years ago have been found by archaeologists. </li></ul><ul><li>Pottery is the oldest form of ceramic products. </li></ul><ul><li>Ceramics are made from clay such as kaolin .Kaolin is rich in kaolinite (hydrated aluminosilicate, Al 2 O 3 .2SiO 2 .2H 2 O). </li></ul><ul><li>When the clay is heated to a very high temperature, it undergoes a series of chemical reactions and is hardened permanently to form ceramics. </li></ul><ul><li>These chemical change are not reversible and the ceramic cannot be melted and remouled. </li></ul>
Properties And Uses Of Ceramics <ul><li>General properties of ceramics are as follows. </li></ul><ul><li>(a) Very hard and strong </li></ul><ul><li>(b) Brittle </li></ul><ul><li>(c) Chemically inert and does not corrode </li></ul><ul><li>(d) Good insulator of electricity and heat </li></ul><ul><li>(e) Very high melting point </li></ul><ul><li>(f) Resist compression </li></ul><ul><li>* Unlike glass, ceramics can withstand high temperature and do not melt easily. </li></ul>
Uses of Ceramics Artifical teeth ang bones Medical and dental apparatus Inert and non- compressible Spark plugs, insulators in ovens and electric cables Insulating parts in eletrical appliances Electrical insulators Lining of furnase, engine parts Insulation Very high melting point and good insulator of heat. Cooking pots, plates, bowls Kitchenware Chemicaaly inert and non-corrosive Vases, porcelain ware, sinks, bathtubs Decorartive pieces and household items Attractive, easily mouled and glazed Tiles, bricks , roofs, cement, abbrasive for grinding Building materials Hard and strong Examples Uses Properties
Thank You !! Preparing by :- LING MEE CHONG (Group 5)
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