Compare and contrast area and volume

Area is a region bounded by a CLOSED path, curved path or path with line segments.  Area is usually a two dimensional physical quantity, a designated part on a plane.  An example the surface of a table, face of a wall or a ceiling.  It can also be a surface in 3-dimensions.  Its units are meter² or centimeter² or feet²  etc. A large agricultural field is a good example of an area.  Normally and ideally no object can reside or exist with in an area. An object requires a volume.  It is a collection of all points enclosed or bounded by the boundary or closed path.  It does not have any thickness.

Volume is a 3-dimensional quantity. A physical body occupies space with its material components. It is the amount of space occupied, that is its volume. Any existing body occupying some space has a mass and volume.  A mass having a volume, has surface area and thickness, a height perpendicular to its surface at each point on the surface.
It is expressed as meter³, feet³ etc.
Volume is a product of surface area (cross-section) and length - for example for a wire or rod.

Some type of thing that was invisible

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.