The stems of cactus plants are thick and round to minimize surface area and store water. Most species of cactus do not have leaves since leaves would allow too much evaporation in the dry desert air.

Water is one of the world’s strangest substances. Most liquids shrink when they freeze but water expands, making it less dense as a solid than as a liquid. That’s why ice floats.

The length of the time you want something to stay cold should be a determining factor in the type of ice you use to cool it.