Cocoa butter is polymorphic: it can set into six crystal structures, each with its own melting point. Chocolatiers aim for form V, which gives a glossy bar that snaps cleanly and melts around 34 °C (93 °F), just below mouth temperature. That's the whole point of tempering. Over time or with heat, the crystals shift and a whitish film appears: harmless, just less pleasant.
Chlorine on its own is fairly gentle. But when it combines with urine, sweat and other grime from swimmers, it forms chloramines, which cause stinging eyes and that classic 'chlorine smell'. A well-kept pool barely smells at all. Shower before you swim and never pee in the water.
Muscle mass slowly shrinks with age, putting independence at risk. But in 1990, a study had nursing home residents aged 86 to 96 train their legs for eight weeks: their strength more than doubled. Muscle responds to training at any age. Getting up from a chair without using your hands is already an exercise.