25 is a colloid (a colloid is a mixture in which liquids which usually don't dissolve are held together in suspension. In the case of mayonnaise, the liquids are water and oil, held together by egg).
In 28, the answer is none of the above. This is because the mass of an object is the same regardless of gravity. However, WEIGHT, which is not the same as mass, can be altered by gravity.
In 0, the cup with hot water will dissolve the salt first. This is because any type of reaction requires energy to operate, even dissolution, which is a physical change. As you add more heat to the system, the salt ions gain more energy and form individual anions and cations (they dissolve). Therefore, more heat = faster reaction.
