The children will determine how many pennies (or counters) it takes to sink a container, so ask them to predict whether a larger container will take more or less pennies to sink.
Invite the children to float a small container in the water tub. Have them place pennies or counters into the container until it sinks. Remove the pennies from the water.
Have the children try the same thing with a larger container and see if it takes more or less pennies than were used for the small container.
Have the children count the pennies and compare the quantities for each container. Write down their results for future comparison.