The bright green of vegetables comes from chlorophyll, which has a magnesium atom at its heart. Acids released by the vegetable as it cooks swap that magnesium for hydrogen, and the pigment turns olive drab. Hence the chef's routine: plenty of boiling water, a short cook, lid off at first so some of the volatile acids can escape, then a quick dunk in ice water.
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.