Introduce the children to a real life fundamental understanding of what heavy and light means. Lay out a series of physical objects that are considered either heavy or light. Examples include a dumbbell, a feather, a gallon of liquid and a jump rope. Have the children handle the objects and describe whether they are heavy or light. Once an understanding is reached, have them separate the items accordingly.
Move from the physical world to schemas. Show a group of children images of objects that can be easily categorized into heavy or light. The images should be of things they may find in their own home or in the classroom such as a washer and dryer, a bureau, a pen and a pair of glasses. Elevate the children's understanding by having them categorize the objects without handling them.
Give each child a series of images on small cards. The images need to be easily recognizable as either light or heavy. Have the child separate the images into two groups, light and heavy. Removing the children from groups and forcing them to think on their own gives them a deeper and more personal understanding of weight.
Introduce the children to the mathematical side of weight. Present a series of objects and have the children try to arrange the objects from heaviest to lightest. Then, while the children watch, weigh the items on a scale and put the weights up on a chalkboard. Rearrange the items if need be. Explain to the children why they were correct or incorrect. Switch out some of the objects and repeat.