Why do icecubes (on regular plastic trays) sometimes pop up cleanly, sometimes all shattered?
You’re going to get inconsistent results outside of a laboratory, because there are a lot of variables that go into the strength of ice. (In fact, “strength” itself is several different attributes of a substance: toughness, hardness, stiffness, etc depending on what kind of force you’re subjecting it to.) Some of the variables that go into the strength of ice: • How quickly it freezes. Slow freezing produces large, clear, very strong blocks of ice, partly because all of the dissolved gases have a chance to be pushed to the outside. (There’s often a cloudy bit in the center, though, because of the way ice freezes from the top down, due to the way ice floats.) You can get one very large crystal if you freeze it slowly enough, or a lot of tiny crystals which are actually better at handling a shock. • How cold it is. Even well below 32, there are microscopic pockets of unfrozen water in the crystal. • Dissolved gases. Gases interfere with the structure of the crystal, which can actually ma