Sink or Float

Objective:
Students will be able to state observations of how an object’s density relates to its ability to sink or float in water.

Fun Facts:

• Liquids vary in their density, too. Try mixing corn syrup, oil and water together. The corn syrup sinks to the bottom because it is dense.
• The shape of an object can also determine if it sinks or floats. A ball of clay sinks right away.
• Objects filled with air also float.
  

Materials:
You will need some sort of bucket, bin, sink, bathtub, etc., filled with water for the sink-or-float experiments.

1. Ask questions such as what do items that sink have in common, what do items that float have in common, etc.
2. Before the students experiment, they will need to make predictions as to whether they think the objects are going to sink or float.
3. What does it mean when we say “Make a prediction?"
4. To make an educated guess about what will happen.
5. Students can use the “Sink or Float Handout” page to make their predictions. Show students each individual item and have them make a prediction by drawing a line from that item to either “sink” or “float” in the picture.
6. Then place one item at a time into the tub of water to find out whether the item sinks or floats.
7. When all items have been tested, refer to the results handout.

Follow-up (Ask the students):

• How many did you get right?
• Did some items sink that you thought would float? Why do you think so?
• Did some items float that you thought would sink? Why?
• Do you think that the shape of the object affects whether it will sink or float?
• What do all of the objects that float have in common?
• What do all of the objects that sink have in common?
• Does the size/material of an object affect its buoyancy? How?
• Do you think your results would be different if you used a liquid other than water? For example, apple juice. How could you test that?

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