A student likes to attend football games, no matter how cold and snowy the weather becomes. She is going to a game on a very cold day and takes along a hand warmer. She activates it and tucks it into the glove she is wearing. She holds her hands together, and before long, her hands are warm. Which best describes how her hands were warmed?

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.