Dissolving a solute such as koh in a solvent such as water results in

Answer;
A decrease in the vapor pressure of the liquid. 

Dissolving a solute such as potassium hydroxide in a solvent such as water results in a decrease in the vapor pressure of the liquid. 

Explanation; 
The vapor pressure of a liquid is the equilibrium of a vapor above its liquid.
In other words it is the pressure of the vapor resulting from the evaporation of a liquid above a given sample of the liquid in a closed container.
The vapor pressure of a liquid in a closed container depends on the temperature.

Yes it would be a physical change.

Answer:

5.6⋅10−^19  j

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