Have your students use balance scales to find objects that weigh the same (or close to it). For example, have them place one wooden block on one side, and another wooden block on the other; the scales should balance. Then try to help them identify other items that weigh the same. Put one nickel on one side, and ask them to add pennies to the other side until it balances. Or have them weigh different types of small toys (such as cars or counting bears) until the sides balance again. This will help your children learn about weights and balance.
Let your students explore how size affects weight by having them place items of different sizes on the balance scales. For example, a large wooden block will weigh the scales down more than a small wooden block. A baseball will weigh the scales down more than a marble. A chalkboard eraser will weigh them down more than a pencil-top eraser. Have students explore your classroom to find similar items in different sizes and determine which one weighs more. This will help them learn about size and proportion as it relates to weight.
To build on the last idea, give students items of different sizes and densities to see if they can predict which one will be heavier. For example, a large feather weighs less than a small marble. A cotton ball and a rock of the same size will not have the same weight. Give students various pairs of items of differing densities and ask them to predict which one will be heavier before placing the items on the balance scales. Help them understand that size isn't the only thing that determines how heavy an item will be; density also matters. To illustrate this idea, you can place an empty cup on each side of the scale, and then slowly fill one of the cups with water. As the water makes the cup more dense, it becomes heavier than its empty counterpart.