STEM Activity to Try at Home: Sink or Float
Kids are naturally curious about floating and sinking. Why does a heavy boat float while a small rock sinks? Would a boat sink if an elephant sat on it? Sometimes objects sink because they’re heavy or dense, but other times it’s because they are buoyant! This STEM activity will provide an opportunity for you and your child to make predictions and observations about floating and sinking.
You will need:
a large plastic container filled with water (or the bath tub during bath time)
objects collected from around the house
Procedures:
Walk around your house with your child and collect items you’d like to test out.
Fill a large container with water (or the tub).
Have your child choose one object at a time. Ask: "Do you think it will sink or float? Why?" Have your child place the object in the water and observe what happens. (Optional: Record the result on the recording sheet. You can have your child draw a picture or write the name of the object or model writing and drawing the object yourself.)
Repeat this for all the objects.
Ask: "Why do you think some objects floated and some sank? Is there anything the same about the objects that floated? How about with the objects that sank? "
Introduce the word "density" to your child. Explain that whether an object sinks or floats depends on its density. Everything is made of molecules. Molecules are tiny particles that can only be seen with a microscope. Some objects have molecules that are packed closely together. Others have molecules that are packed more loosely. That is density. Objects with tightly packed molecules are denser and sink. A paper clip or a penny is dense. Objects with more loosely packed molecules are less dense and float.