The 1st law of thermodynamics doesn't specify that matter can be created nor destroyed, but that the total amount of energy in a closed system cannot be created nor destroyed though it can be changed from one form to another.
D! the molecules of the warmer water would have a higher average kinetic energy :)
Answer: C.) polyatomic anion
Explanation: Cations are the ions which carry a positive charge and anions are the ions which carry a negative charge. Monoatomic ions are those which consists atoms of similar elements and polyatomic ions are those which consists of atoms of different elements.
For example : 
is a monoatomic cation.
is an monoatomic anion.
is a polyatomic cation.
is a polyatomic anion as it consists of atoms of phosphorous and oxygen and bears a negative charge.
Answer:
63.5474U.M.A. es la masa atómica promedio del cobre
Explanation:
La masa atómica promedio de un átomo es definida como la suma de las masas de los isótopos multiplicada por su abundancia. Para el caso del cobre que tiene dos isótopos:
Cu = Masa 65Cu*Abundancia + Masa 63Cu*Abundancia
Reemplazando con los valores dados en el problema:
Cu = 62.9298U.M.A.*0.6909 + 64.9278U.M.A.*0.3091
Cu = 63.5474U.M.A. es la masa atómica promedio del cobre
