• Calcium and Magnesium are major components of hard water.

• Hard water is formed when water percolates through limestone or gypsum which is high on calcium and magnesium content.

• Soaps do not act in hard water due to the presence of these salts but detergent is capable to give results in hard water.

• Water softening systems work by reducing the concentrations of minerals from the water.

• The total water hardness is the sum of the molar concentrations of Ca2+ and Mg2+, in mol/L or mmol/L units.

• The symbol of Potassium is K.

• The symbol of Sodium is Na.

• The symbol of Sulphur is S.

• The symbol of calcium is Ca.

• Some other unique symbols are-

Gold-Au

Silver-Ag

Tin-Sn

Lead-Pb

Antimony-Sb

Iron-Fe

Mercury-Hg

Tungsten-W

• The thermosetting polymers is a permanent setting polymer that gets hardened and sets during moulding process and cannot be softened again.

• They are usually soft solid or liquid. Heat provides energy for chemical reactions that increases the cross-linking between polymer chains.

* Brass is an alloy of copper and zinc.

* The proportions of the copper and zinc are varied to yield many different kinds of brass.

* Basic modern brass is 67% copper and 33% zinc.

* It is also called a homogeneous mixture.

• Zink Sulphate has the formula ZnSO4.7H2O.

• It was historically known as "white vitriol".

• Vitriol is an archaic name for a sulfate.

• In medicine it is used together with oral rehydration therapy (ORT) and an astringent.

• The cotton cloth will readily catch fire comparative to other fabric.
• Cotton is highly flammable.  
• It burns easily and rapidly and not stick to the body of human that's why it is more preferred for wearing purpose.

• Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The chemical formula of ‘quartz’ is SiO₂.

• It is the most powerful healing stone of the mineral kingdom & is second most common mineral in the Earth’s crust.

• The pH of water is 7.0 at about 25 deg C or about 77 deg F.
• Pure water undergoes a reversible reaction in which both H+ and OH- are generated.

• Carbon-dioxide is a chemical compound composed of one carbon and two oxygen atoms.

• It is often referred to by its formula CO2.

• It is present in the Earth's atmosphere at a low concentration and acts as a greenhouse gas.

• In its solid state, it is called dry ice.