When sodium metal is added to water, an orange flame is observed on the metal surface. based on this observation, what can best be concluded?

a physical change occurs because the metal gets smaller.
a chemical reaction occurs because the liquid becomes cloudy.
a chemical reaction occurs because heat and light are given off.
a physical change occurs because vapor is released into the air.

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.