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amy gon 4 December 2012
Transcript of Silicon Dioxide
Synthetic Amorphous Silica
Synthetic amorphous silicon dioxide
Amorphous precipitated silica Silicon Dioxide Makes sense right? One part
silicon Di meaning
two Oxide, as in oxygen What does Silicon Dioxide look like? What is silicon dioxide? Characteristic Properties The ratio of silicon atoms to oxygen atoms is... 1:2 or... Si1:O2 This presentation that I made is awesome, just like me, by... Go together for phase change diagram. Solubility alkali (only very slightly)
hot KOH and NaOH solutions
hydrofluouric acid (no other acid otherwise) Melting/Freezing Point The melting/freezing point of SiO2 is 1610˚C (2930˚F). Boiling/Condensing Point The boiling/condensing point of SiO2 is 2230˚C (4046˚ F) Solid melting/freezing point Liquid Boiling/
condensing point Gas Endothermic Change Exothermic Change When a substance is heated up, it is goes through endothermic change (where energy is absorbed). Molecules in a substance are organized at the liquid form and the forces of attraction are strong enough to hold the substance together both its size and shape. When the substance is heated and it starts to absorb energy, the molecules vibrate around their fixed positions and become disorganized. The substance has changed into a liquid through a process called melting. The forces of attraction in a liquid are not as strong as in a solid so when the liquid substance is not contained, it will spread out. Further heating of the substance causes it to change again from a liquid to a gas in the process of vaporization. The molecules have enough energy to move from their positions and they bounce around the container randomly. Because they bounce with the great amount of energy they have, they can fill any size container and spread out as much or as little as allowed. The opposite change takes place when a substance is cooled down and it releases energy called exothermic change. These laws apply to all substances, including to the compound Silicon Dioxide (SiO2). The kinetic energy increases because of absorption of energy through endothermic change. More energy is needed when molecules are heated and start to move and vibrate. Crystalline Amorphous The crystalline form of it is overall called quartz and can show up in many different forms, shapes, sizes and colors (potentially with other substance in a mixture). The ratio of silicon to oxygen is 1:2 so it's kinda like... Si1 & O2 The amorphous form of Silicon Dioxide is like a white powder/sand. Silicon Dioxide is a solid or granular solid at room temperature, but must be heated to extreme temperatures to melt and even further, boil. When heated to such temperatures, Silicon Dioxide undergoes endothermic change. It takes more energy to move so energy (in the form of heat) must be absorbed. When Silicon Dioxide cools down, it releases energy to become a liquid or even further a solid. Now you'll notice that if we look way back to this part, I mentioned Silicon Dioxide in its crystalline form is quartz. It's true! Sand is also silicon dioxide with other substances in a mixture. The picture of the amorphous form is pure silicon dioxide sand. The element Silicon was discovered by a Swedish chemist, Jöns Jakob Berzelius in 1824 but it is difficult to tell when the compound Silicon Dioxide was discovered because it has been around as long as we can count. Silicon dioxide is one of the most common compound in the earth's crust. In the early days of mankind, flint (a form of quartz, the crystalline state of Silicon Dioxide) was used to make fire.
The amorphous form (like sand) can be used to make glass and porcelain for pottery, etc. Ever heard that silica sand is what's used to make glass? Same compound...
Silicon dioxide is also used when making transistors (like a switch for devices such as computers, phones, toys, appliances, and a large assortment of other electronic things. Imagine how many transistors that would be!
Have you ever seen those
little silica packets that come
in packages or small boxes?
Those silica packets absorb
moisture so the contents of
the package aren't ruined. Uses and Facts I hope you learned a lot about Silicon Dioxide from the presentation. Thanks for watching!