Two beakers contain clear, colorless liquids. when the contents of the beakers are mixed a white solid is formed. is this an example of a chemical or a physical change?

Agas has a volume of 0.7 l at 300 mmhg. what would be the new volume at 900 mmhg

1)each group 16 element has how many valence electrons? ( )4 ( )6 ( )8 ( )16 2)how many dots appear in the dot structure for calcium ion, ca2+? ( )zero ( )one ( )two ( )eight 3) which of the following atoms forms a cation to obtain an octet of outer shell electrons? ( )magnesium ( )oxygen ( )fluorine ( )helium 4) an al3+ ion contains 13 protons and 10 electrons. ( )true ( )false 5) valence and non-valence electrons are represented in lewis dot structures. ( )true ( )false

Explain in detail of the four major scientific developments that spurred the formulation of the plate tectonics theory