I would go with 7 because its just water.
Netural atoms lose electrons or gain electrons to form ions. Either positive or negative ions.
Positive ions:
Na ---> Na+ + e-
Negative ions:
Cl + e- ---> Cl-
Let the water evaporate and you'll be left with the sugar, or boil the water and collect the steam. the sugar will be left in the container you boiled the water in and you'll still have the water from the steam.
During the experiment, scientists noted that several of the reaction beakers became hot to the touch. All of the following reactions could cause this result except endothermic and positive ∆H experiments.
<u>Explanation:</u>
If the beakers are becoming hot during experimentation, then that means the energy is being released from the reactants during this experiment. As the energy is being released that enthalpy change will also be negative as the enthalpy change is calculated as the difference of enthalpy of reactants from products.
So in these cases, heat is released making the beakers hot. So for the exceptional case, the experiment should be endothermic in nature and positive enthalpy change should be there in the experiment. Such that the heat will not be released leading to no heating of beakers.
