Why is the loss of mass of the object only an apparent loss?

If i make a solution by adding 83grams of sodium hydroxide to 750ml i’d water what is the molarity of sodium hydroxide

If 1.8 l of water is added to 2.5l of a 7.0 m koh solution, what is the molarity of the new solution

Temperature is defined as a. the equivalent of heat. b. a measure of the average kinetic energy of the individual atoms or molecules composing a substance. c. how hot or cold it is. d. the total kinetic energy of the atoms or molecules composing a substance. e. none of the above is correct.