Answer:
Copper turns green on exposure to air
Explanation:
Liquid water freezes to form ice: Physical change
Reason: Water can melt back when it becomes ice.
Copper turns green on exposure to air: Chemical change
Reason: The copper can not change back from the green state when it turns green.
From the equation of the reaction; for every 1 mole of copper, the reaction uses 2 moles of silver nitrate.
<h3>What is a reaction?</h3>
A chemical reaction involves the transformation of one chemical specie into another. The reaction is not shown here hence the question is incomplete.
However, the reaction should be of the sort; Cu + 2AgNO3 ---> Cu(NO3)2 + Cu. Thus, for every 1 mole of copper, the reaction uses 2 moles of silver nitrate.
Learn more about chemical reaction: brainly.com/question/6876669
This is a reduction half-reaction. Initially, gold exists as

, and after the reaction, it has been converted to elemental gold. To make this possible, three electrons must be added to <span>

. This fits within the definition of reduction reactions, where the reactant gains electrons in the reaction.</span>
Digestive I think, that transfers food.
Because during combustion reaction, heat energy is released and it's this energy that is converted to work