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Silicon dioxide

From Academic Kids

Properties
General
Name Silicon dioxide
Chemical formula SiO2
Appearance Transparent solid
Physical
Formula weight 60.1 amu
Melting point 1986 K (1713 °C)
Boiling point 2503 K (2230 °C)
Density 2.6 ×103 kg/m3
Crystal structure Quartz, cristobalite or tridymite
Solubility 0.012 g in 100g water
Thermochemistry
ΔfH0gas -305.43 kJ/mol
ΔfH0liquid -899.86 kJ/mol
ΔfH0solid -910.86 kJ/mol
S0gas, 1 bar 228.98 J/mol·K
S0liquid, 1 bar  ? J/mol·K
S0solid 41.46 J/mol·K
Safety
Ingestion Low hazard.
Inhalation Irritation, long term exposure of the crystalline form causes silicosis.
Skin May cause irritation.
Eyes May cause irritation.
More info Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/10/9916.html)
SI units were used where possible. Unless otherwise stated, standard conditions were used.

Disclaimer and references

The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2.

It is found in nature in several forms, including quartz and opal. In fact, silica has 17 crystalline forms (see Nomenclature of Silica (http://www.minsocam.org/MSA/collectors_corner/arc/silicanom.htm)). Also, many forms of life include silica structures, including microorganisms such as diatoms, plants such as horsetail, and animals such as hexactinellid sponges.

It is manufactured in several forms including glass (in colorless high purity form called fused silica), synthetic amorphous silica and silica gel (used e.g. as desiccants in brand new clothes and leather goods). Silica is a major ingredient of Portland cement. The ceramic re-entry heat protection tiles mounted on the bottom side of the Space Shuttles are made mostly of silica, as are the firebricks used in steel processing.

The most common constituent of sand in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide), usually in the form of quartz because of the considerable hardness of this mineral. However, the composition of sand varies according to local rock sources and conditions.

Inhaling crystalline silica dust can lead to silicosis.

Further reading

de:Siliziumdioxid es:Dixido de silicio fr:Silice it:Silice nl:Silica ja:二酸化ケイ素 pl:Krzemionka ru:Диоксид кремния sv:Kiseldioxid zh:二氧化硅

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