The setting and hardening of cement is a complex chemical process involving the hydration of calcium silicates and aluminates. When water is added, it reacts with the cement components to form a rigid, interlocking crystalline structure.

Portland cement is manufactured by heating a mixture of limestone (calcium carbonate) and clay (silicates/aluminates) in a kiln to form clinker. Gypsum (calcium sulfate dihydrate) is added to the ground clinker to regulate the setting time of the cement, preventing it from hardening too quickly upon the addition of water.

Glass is an amorphous solid that lacks a long-range crystalline structure. It is often referred to as a supercooled liquid because it is formed by cooling a liquid rapidly enough to prevent crystallization, resulting in a disordered, glass-like state that retains some liquid-like structural characteristics despite appearing solid at room temperature.

The green color in glass is often caused by iron impurities. Manganese dioxide is added to the glass melt to act as an oxidizing agent, converting ferrous iron to ferric iron, which has a much less intense color, effectively neutralizing the green tint.

Pyrex glass, a borosilicate glass, is widely known for its high thermal shock resistance due to its low coefficient of thermal expansion. The provided answer 'flint glass' is typically used for optical lenses due to its high refractive index and dispersion, not for heat resistance. This suggests a potential factual error in the source key.

Bleaching powder, chemically known as calcium hypochlorite or calcium oxychloride, is manufactured by passing chlorine gas over dry slaked lime (calcium hydroxide). The reaction is represented as Ca(OH)2 + Cl2 -> CaOCl2 + H2O. This process is essential for producing a stable, solid form of chlorine that can be easily handled and used for disinfection and bleaching purposes.

Crookes glass, often misspelled as 'crooked glass', contains cerium oxide, which gives it the unique property of absorbing ultraviolet light while remaining transparent to visible light. It is frequently used in the manufacturing of sunglasses to protect eyes from UV damage.

Fibre glass is a material consisting of extremely fine fibers of glass. It is commonly used as a reinforcing agent for many polymer products to form a composite material known as glass-reinforced plastic (GRP) or fiberglass. This material is valued for its high strength-to-weight ratio and durability in various industrial and construction applications.

Photochromic lenses contain silver halides (like silver chloride) dispersed in the glass matrix. When exposed to UV light, these silver ions are reduced to metallic silver, which darkens the lens. When the UV source is removed, the reaction reverses, and the lens clears.

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