Answer:
The principle of conservation of physical quantities such as mass, weight and volume is part of Piaget's theory aimed at studying children's ability to perceive their permanence independent of changes in form. In the construction of this process it is possible to identify the level of children's cognitive development.
The notion of conservation is an internalization that is achieved through a process. It is not acquired since the child has the possibility to think because to internalize it in the plane of thought it is necessary to learn first in the plane of action and experience.
Four-year-old Daniel answers the question incorrectly, while seven-year-old Emily is able to answer the question correctly because according to Piaget's theory of child development, children who are in the "early preoperative" stage fail in conservation tasks. Children who are in the "late preoperative" stage do succeed in some of these tasks, but do not have the capacity to provide adequate justifications for their judgments. Only when children enter the "concrete operational" stage that they manage to provide logical justifications for everything that has to do with conservation.