Water-Ice Equilibrium And Le Chatelier's Principle
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Water-Ice Equilibrium And Le Chatelier's Principle

Water, like other matter exists in three states: solid, liquid and gas. Each of these states has its equilibrium conditions that are affected by changes in their environments (e.g. change in temperature, pressure, concentration, etc). In 1884, Henri Louis Le Chatelier discovered an equilibrium principle that became known as Le Chatelier's Principle
(a) State Le Chatelier's Principle.
(b) What is implied if liquid water and ice is in equilibrium?
(c) Figure 14.7 is the inside of a thermos from a top view. It shows water and ice in equilibrium at 0oC. What will happen to the water-ice equilibrium in the thermos if a 100oC copper penny is dropped into the thermos?
(d) What will happen if instead of dropping the hot penny as in (c), a cold penny at -100C is dropped into the thermos?
(e) Why is it difficult to skate in very cold ice (temperature very much below 0oC)?

The strings: S7P7A72 (equilibrium-dynamic).

The math:
Pj Problem of Interest is of type equilibrium (equilibrium-dynamic).

(a) Le Chatelier's Principle: If stress is applied to a system at equilibrium, the system will tend to readjust so that the stress is reduced.

(b) At equilibrium, there is no net change as a consequence of their interaction. H2O (l) <-----> H2O (cr).

(c) The hot penny will loose heat and the heat it lost will be absorbed by the water-ice mixture. Some ice will melt until the system (water-ice mixture, penny) is returned to the equilibrium temperature of 0oC. This readjusted equilibrium will have more water and less ice.

(d) The cold penny will absorb heat from the water-ice mixture until the system (water-ice mixture, penny) is returned to the equilibrium temperature of 0oC. This readjusted equilibrium will have more ice than water because some of the water became ice.

(e) Easy skating on ice requires a critical range of thickness of the layer of water on the surface of the ice. A thin layer (below the lower bound of the critical thickness range) of water on the surface of the ice causes insufficient slickness on the surface of ice. Consequently, friction between the skate and the ice is higher than required for easy skating.

Blessed are they that have not seen, and yet have believed. John 20:29