Tag: science & technology

Bromine is the only nonmetallic element that is liquid at room temperature, appearing as a reddish-brown volatile liquid. It evaporates easily to form a red-brown gas. Bromine is neither a solid, colorless gas, nor highly inflammable.

Diamond is the hardest known natural material, composed of carbon atoms arranged in a tetrahedral lattice structure. Each carbon forms four strong covalent bonds, creating extreme hardness. Gold, coal and platinum are all much softer on the Mohs scale.

Peat is the lowest grade of coal where recognizable plant material remains visible due to minimal decomposition. Lignite, bitumen and anthracite represent progressively more compressed and altered coal where original plant structures are no longer identifiable.

Tetraethyl lead was historically added to petrol (gasoline) as an anti-knocking agent to prevent engine damage. It is not used as a pain killer, fire extinguisher or mosquito repellent. Its use has been phased out due to lead toxicity.

Graphite's layered structure allows sheets to slide over each other easily, making it an effective solid lubricant especially at high temperatures. Silica and iron oxide are abrasive, not lubricating. Diamond is the hardest substance and used as an abrasive, not a lubricant.

Helium is used in diving gas mixtures (like Heliox) because it's inert and reduces nitrogen narcosis risk at depth. Unlike nitrogen, helium doesn't dissolve into tissues as readily, decreasing decompression sickness risk.

Oxy-acetylene welding uses oxygen and acetylene to create an extremely hot flame (~3200°C) suitable for welding and cutting metals. Acetylene provides the fuel, while oxygen supports complete combustion.

Deliquescence occurs when a hygroscopic substance absorbs so much water vapor from air that it dissolves in the absorbed water and forms a solution. Common examples include calcium chloride and sodium hydroxide.

Silicon carbide (SiC) is an extremely hard material (9-9.5 on Mohs scale) used as an abrasive for cutting and grinding hard materials like stone, concrete, and metals. It's also used in abrasive wheels and cutting tools.

The average salinity of seawater is approximately 3.5% (35 parts per thousand). This means about 35 grams of dissolved salts per kilogram of seawater, primarily sodium chloride.