Final answer:
During the concrete operational stage, children develop the ability to reason logically about real events. They have a firm grasp on numbers, understand mathematical operations, and can recognize that the properties of objects remain the same even if their appearance changes.
Step-by-step explanation:
In Piaget's theory of cognitive development, the concrete operational stage occurs from about 7 to 11 years old. During this stage, children can think logically about real (concrete) events. They have a firm grasp on the use of numbers, understand transformations, and can perform mathematical operations. They also master the concept of conservation, which means they understand that even if something changes shape, its mass, volume, and number stay the same.