A change in which two or more substances combine to make a new substance

An occluded front moves over the farmland that has been experiencing drought conditions. what change in weather will this front likely bring? a. gray skies, but no rain b. an extended period of rain c. more dry air and sunny skies d. violent, short-lived thunderstorms

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

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