A. properties which can be observed since it's what you're physically viewing
Answer: The green copper (II) carbonate 
changes to black copper oxide 
Explanation:
Decomposition is defined as the chemical reaction in which a single compound gives two or more simple substances. It requires energy to break the bonds between reactants, thus is an endothermic process.
Thermal decomposition uses heat for decomposition.
The chemical equation for thermal decomposition of copper (II) carbonate is:
The green copper (II) carbonate changes to black copper oxide
If you count the number of electrons (small dots), you have the atomic number. In this case you have 11 so this atom is a sodium atom. Sodium has 1 valence electron (electron on the outer shell) and chlorine has 7. This means that if sodium gave one electron away and chlorine would obtain one electron, they would both have the (ideal) noble gas conformation (full outer shell).
Synthesis reaction is a reaction where two or
more substances combine to form a new compound. <span>It
is a reaction which releases energy in the form of heat and light. Therefore,
it is an exothermic reaction. </span>From its the definition the correct answer is the third option where carbon dioxide and water combine to form carbonic acid.
