Frozen water butt problems

The other winter, the spell of freezing weather that went on for weeks caused a problem with our water butt. Water freezes from the top down - that's the reason life survived on Earth as it could survive under the ice sheets on frozen oceans. Here, the problem is that it also explands as it freezes. The stuff that freezes first at the top doesn't expand upwards anticipating the lack of space. This means that the stuff that freezes last at the bottom has no space into which to expand. It thus expands downwards, pushing out the flat plastic bottom into a rounded shape. The water butt was free to wobble on its round bottom and it fell over. Water is H2O. The hydrogen atoms in one H2O molecule are attracted to the oxygen atom in the next water molecule. This is called hydrogen bonding. At ordinary temperatures, the heat energy is enough to wobble the molecules out of fixed bonding patterns. But as water freezes, the molecules can form fixed hydrogen bonds, making the H2O into a solid. These fixed bonds give the water a rigid molecular structure, like scaffolding, and this opens up gaps, pushing the molecules apart. Google it for a more scientific explanation and diagrams!