When wood absorbs water, expands, and breaks stones, how is conservation of energy working? There is a traditional stone cutting method consisting of making a series of small holes in the stone, then inserting wood into the holes, and then adding water to the wood. When the wood expands, it will break the stone. 
How is energy being conserved, when the stone is being broken by the expansion of the wood?
 A: Dry wood consists of air-filled pores surrounded by cellulose fibers and lignin. As such it has extremely high internal surface area, all of which possesses a certain amount of surface energy, which has the ability to perform work. An easy way to get it to perform that work is by bringing the wood into contact with water. that surface energy then does work by drawing water up into the open-celled structure of the wood to wet out those surfaces and fill all the pores. Since the pores are very small, the radius of curvature of the air/water meniscii that are in contact with the cell surfaces in the wood are tiny, and the Young-Laplace pressure jump across them is correspondingly large. This causes the water to wedge the cell structure open as it wets out the wood, causing it to swell. the forces developed in this process are sufficient to break rocks.
The classic demonstration of this effect is one in which a cylindrical container of dry pinto beans is filled with water, fitted with a piston, and slid under the rear axle of a car to produce a snug fit. 12 hours later, after the beans have rehydrated themselves, the car's axle will have been lifted up by several centimeters by the expansion of the beans.
A: I think the deleted answer by @naiad (wet wood has higher entropy than [water] and [dry wood] separately) may make sense. It is well-known that wood dimensions change depending on the humidity of the surrounding air. If water is concentrated in some area, its contribution to entropy is lower than if it is dispersed. Therefore, energy can be supplied from the environment, which is maintained at some relatively constant temperature.
Another possible explanation: capillary action (absorption of water by wood) is caused by intermolecular forces, so the potential energy of intermolecular forces decreases in the process.  
