Introduction to Surfaces and Colloids - Surface and Colloid Chemistry: Principles and Applications - page 4

FIGure 1.3 Insect strides on the surface of water.

FIGure 1.4 An iron needle floats on the surface of water ( only if carefully placed ; other-
wise, it should sink due to gravity forces).

Solid surfaces can similarly exhibit additional characteristics, where solid and solid 2
interact (such as in: cement, adhesives, etc.)

1. Solid 1 -solid 2 (cement, adhesives)

An analogous case would be when the solid is crushed and the surface area
increases per unit gram (Figure 1.5). For example, finely divided talcum powder
has a surface area of 10 m 2 /g. Active charcoal exhibits surface areas correspond-
ing to over 1000 m 2 /g. This is obviously an appreciable quantity. Qualitatively,
one must notice that work has to be put into the system when one increases the
surface area (both for liquids or solids or any other interface).