Sink or Float
Presented by
Emily Duncan
Southwestern University
duncane@southwestern.edu
Children will learn what makes something float or sink. They will learn what makes boats float. They will also explore the different sizes and shapes of boats.
6. Science concepts. The student knows that systems have parts and are composed of organisms and objects, the student is expected to:
A. Manipulate, predict, and identify parts that, when separated from the whole, may result in the part or the whole not working, such as flashlights without batteries and plants without leaves;
B. Manipulate, predict, and identify parts that, when put together can do things they cannot do by themselves, such as a guitar and guitar strings
7. Science concepts. The student knows that many types of change occur. The student is expected to:
A. Demonstrate a change in the motion of an object by giving the object a push or pull
Start off with your students meeting with you in a circle on the floor, with several items that float and several items that sink. Ask them to predict what will sink and what will float. Talk to them about why they think an object floats or sinks. After you think your students have a good grasp on what types of objects float and what types of objects sink break your class up into groups of 2 or 3. Give each group a piece of modeling clay; tell them their goal is to make a boat, out of the modeling clay that will float. Place several buckets of water around the class room that the children can go and test out their boats. After the children have successfully made their boats float present them with a new challenge of seeing how many paper clips they can put on their boat before it sinks. Encourage the students to continue to make changes to their boats every time it sinks. Follow up the lesson with a class discussion. Ask them, how did they build their boats? What type of boat designs worked the best? What caused your boats to sink? How did they change the size and shape of your boats make them float better?
Every object takes up space. All objects in or on water push water aside, because they need space. This is called displacement. Water is not easily compressed. If an object tries to push it down it will quickly push it back up. This upward pressure on the object can cause it to float. A boat floats because it is buoyant. Buoyancy is the tendency to float or rise in a fluid. Boats can float because they are filled with air. Boats can float if the overall density of the boat is less then the density of the water. If the overall density of the boat is more than the density of the water the boat will sink.
Adapted from: http://www.biology.duke.edu/cibl/exercises/clay_boats.htm