Ben and Jerry added small pieces of magnesium to hydrochloride acid. They noticed that bubbles formed, the test tube got hot, and the the magnesium disappeared. What is a sign that a chemical reaction has taken place in this experiment

the answer to this question is 3.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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