What type of substance is NaOH?

NaOH is Sodium Hydroxide ( Caustic Soda / Lye). It is an alkali.

In solid form it is a white crystalline solid. In liquid form it is colourless oily liquid, corrosive to the touch.

As an alkali it has a pH ~ 12 .

An Alkali is is a soluble base. The BASIC Component is sodium oxide (Na2O) which has been dissolved in water.

Na2O + H2O = 2NaOH.

It contains ;

1 atom of sodium (Na ; latin for Nadium)

1 atom, of oxygen (O)

1 atom of hydrogen (H)

To distinguish them from acids , alkalis are always written '--OH'. whereas acids are always written as 'H---'.