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Glass was first produced in ancient Egypt.
4.6.1 Describe the composition of glass.
Glass is composed primarily of silicon dioxide together with some sodium oxide and calcium oxide and small quantities of a few other chemicals.
4.6.2 Explain that glass is produced from sand, limestone and sodium carbonate, and requires large quantities of energy for its manufacture.
Scrap glass is added to new raw materials to make the process more economical.
Glass is produced from all these elements and needs a lot of energy. This is because the in order to produce glass the first thing is to melt all elements, this takes a tremendous amount of energy due to the very high melting points of the materials.
Glass furnace temperatures reach up to 1675°C adding scrap glass leads to savings not only in the raw materials, but also in the energy consumption of the glass furnace.
A video from the NAM of the manufacturing of glass bottles from the mixing of raw materials to labelling.
4.6.3 Describe the characteristics of glass.
Consider brittleness, transparency, hardness, un-reactivity and aesthetic properties
Characteristics of glass:
4.6.4 Explain that the desired characteristics of glass can be accurately determined by altering its composition.
Consider soda glass and Pyrex®.
Soda glass is made of oxides of silicon (SiO2), calcium (CaO) and sodium(Na2O). It is the most common type of glass which is used for windowpanes, glass containers for beverages and food.
Soda glass has a medium resistance to high temperatures and sudden changes of temperature (low thermal shock) and a high resistance to corrosive chemicals. To improve the low thermal shock one can alter the chemical composition which to make Pyrex.
NB: For IB no need to know the chemical compounds just FYI
4.6.5 Outline the differences between toughened and laminated glass.
Consider their responses to being flexed and to impact.
The desired characteristics of glass can also be altered in way to produce toughened and laminated glass which respond differently when being deflected and to impact.
4.6.6 Explain why glass is increasingly used as a structural material.
Consider the use of plate glass and glass bricks as wall and flooring materials. Consider material properties, for example, resistance to tensile and compressive forces, thermal conductivity and transparency. Consider aesthetic properties and psychological benefits: allows natural light into buildings and can visually link spaces, creating more interesting interiors.
Plate glass, glass bricks and flooring are used as a structural material due to the:
Bulleted list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.
Images are clickable links to its location.