Freeze/release

It is eustomary for automotive weatherstripping to be coated with silieone or urethane spray to impart a low coefficient of fiiction surface for easy door elosure and freeze release. This is to prevent automobile doors and trunk lids from freezing shut at low temperatures. ... 

Liquid propane and butane will vaporize rapidly if released into the open air, and if they come into contact with bare skin will cause painful freeze burns. Therefore gloves and goggles should always be worn if there is a danger of liquid LPG being released or spilt. 

The manufacture of ice in large blocks is by the can method (see Figure 12.1), where a number of mould cans, filled with water, are immersed to just below the rim in a tank of refrigerated brine. The smallest block made in this way is 25 kg and will freeze in 8-15 h, using brine at -11°C. Blocks up to 150 kg are made by this method. When frozen, the moulds are lifted from the tank and slightly warmed to release the ice block from the sides of the moulds, when they can be tipped out. Blocks may go into storage or for direct use. 

SOLUTION We can expect the entropy of the surroundings to increase when water freezes because the heat released stirs up the thermal motion of the atoms in the surroundings (Fig. 7.17). To calculate the change in entropy of the surroundings when water freezes we write AHfrceze = —AHflls = —6.0 kj-mol 1 and T = ( — 10. + 273) K = 263 K. Then... 

Phase changes can go in either direction Steam condenses upon cooling, and liquid water freezes at low temperature. Each of these is exothermic because each is the reverse of an endothermic phase change. That is, heat is released as a gas condenses to a liquid and as a liquid freezes to a solid. To make ice cubes, for instance, water... 

Schematic view of the spontaneous process for a water-and-ice mixture in a freezer. The energy-releasing process, freezing, is spontaneous under these conditions.

When water freezes, its molecules becomes more constrained, but the energy released in this process becomes more dispersed in the surroundings. 

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