BUOYANCY

"WHAT MAKES IT FLOAT?"

SHORT TERM GOALS:

  1. To allow the students to become more familiar with the connections between the ocean and science, specifically how objects are able to float in the ocean.
  2. To help students see the connections between density, buoyancy, surface area, and water pressure and how all of these concepts are important in making an object float.

TIME ALLOTMENT: 1 1/2hours

CONTENT AREAS ADDRESSED:

(1) Science

(2) Math

(3) Language Arts

CONCEPTS ADDRESSED:

(1) Measuring

(2) Weighing

(3) Analyzing

(4) Observing

(5) Water displacement

(6) Volume

(7) Density

(8) Mass

MATERIALS:

(1) Bill Nye's episode on Buoyancy

(2) TV and VCR

(3) Two liter bottle (empty)

(4) Pipette

(5) Nut

(6) Water

(7) 2 Eggs

(8) 2 Glasses (empty)

(9) Small miscellaneous objects (coin, cork, piece of wood, pen cap, etc.)

(10) Medium sized tub for water

(11) Clay

(12) Marbles for testing buoyancy

(13) Wood blocks

(14) A small round object that will sink (possibly a marble or ball)

(15) Graduated cylinder for testing volume

(16) Ruler

(17) Pen and paper

PROCEDURE:

  1. After a short explanation of the concepts surrounding buoyancy (the ability to float), Bill Nye's episode on buoyancy (lesson 05 on http://nyelabs.kcts.org/) gives an excellent introduction to why objects have the ability to float, along with fun, music, and activities. Allow the students to view this episode before moving into more detailed buoyancy activities.
  2. After watching the buoyancy video, allow the students to discuss the different aspects of an object that allow it to float. The students can brainstorm other objects that they think could float. Make a list of these objects.
  3. After making the list, collect as many of these objects as possible. Make sure to have the following objects as well: coin, cork, pen cap, etc., and a tub of water to test the objects in the water. The students should keep track of which objects float and which ones sink, possibly in the form of a chart.
  4. For explanation purposes, have several other activities to help the students understand why particular objects float or sink (density, weight, surface area, and pressure).
  5. With the activities given, allow the students to view some science experiment books, which can help with understanding and explanation. Possible resources include:

Challand, H.J. (Ph.D.) (1984). Activities in the physical sciences. Chicago: Children's Press. [ISBN: 0-516-00504-9]

Elementary science experiments. (1971). Compton: Educational Insights. [ISBN: 0-88679-352-1]

Schwaller, A.E. (1989). Transportation, energy, and power: Technology. Albany: Delmar Publishers, Inc. [ISBN: 0-8273-3227-0]

Williams, J. (1992). Projects with water. Milwaukee: Gareth Stevens Publishing. [ISBN: 0-8368-0771-5]

 

Activity A--Salt Water vs. Fresh Water

Materials: (Each pair of students will need the materials)

(1) 2 glasses

(2) 2 eggs

(3) Salt and a stirring utensil

Procedure:

  1. Fill 2 glasses about _ full of water.
  2. Add 2 teaspoons of salt into one of the glasses and stir until dissolved.
  3. Add an egg to the fresh water. Observe.
  4. Add an egg to the salt water. Observe.
  5. The students should complete the activity and follow along on the lab sheet which is attached. The students should be able to answer the questions just from their knowledge gained during the experiment.
  6. After the students have grasped the concept of density by testing a variety of objects, introduce the concept of density. Density can be determined by measuring. First make sure the students have the correct materials (wood block, round object like a marble or ball that will sink, graduated cylinder, a ruler, pencil, and some paper).
  7. To test the density of the wood block, the students should have an idea of the formula used to find density (Density = mass/volume). Also give the students the density of water so they can make their comparisons. Allow the students to then find the volume of the wood block by using (length x width x height). Once the students know this measurement, they can move into the mass of the object.
  8. The mass can be found by using a simple scale in which the students place gram weights on the scale to balance out the weight. Then the students can apply this number to the formula to complete the equation. Any other available mass measurements can be used as well.
  9. The rubber ball or marble is not going to be as easy to measure for volume. A graduated cylinder must be filled with water to a certain line, and the students can record the amount of water in the cylinder. Then after the object is dropped into the graduated cylinder, the students should record the number to which the water line rises again. The difference between the two numbers will give the volume of the object, otherwise known as the water displacement method. The mass can be found using the same method as was used for the wood block.
  10. Once the students know the density of the two objects, one square and one circular, they can compare the densities of the two objects to water. In this way, they will know if the objects will float or sink without actually testing them.

 

Activity B--Cartesian Divers

Materials: (Each pair of students will need the materials)

(1) A two liter bottle (empty)

(2) Pipette

(3) Nut

(4) Access to water

Procedure:

  1. Fill a two-liter bottle about _ full of water.
  2. Add a couple drops of water into a pipette and attach a nut to the end of the pipette.
  3. Drop the pipette/nut combo into the bottle of water. Observe.
  4. Cover the bottle. Squeeze the sides of the bottle slightly and observe the pipette.
  5. The students should complete the experiment and answer the questions on the lab report. The students will have a better grasp of water pressure and the effects of weight on water pressure as they are placed in water.

Activity C--Buoyancy and Shape

Materials: (Each pair of students will need the materials)

(1) Clay

(2) Marbles for testing buoyancy

(3) Pen and paper

(4) Tub of water

Procedure:

  1. This activity is to allow the students to see how the surface area of a clay shape affects its ability to float. Give the students a chance to form a flat, circular shape out of the clay and test it in some water.
  2. After testing the flat shape, the students can begin forming the clay into more of a boat shape, making each test a little deeper. The students should keep track of which deepness floats best, etc.
  3. After the students know which shape floats best, allow them to test the buoyancy with marbles and compare each buoyancy with the others. The students can keep track of how many marbles were needed to sink the boat shaped clay of each depth and shape.

ASSESSMENT:

  1. Did each group member contribute to the experiment? Allow the students to fill out the lab reports given out before the experiment. The students can work in partners on the lab report, but have each child fill out a sheet for future reference.
  2. Observation Checklist
  3. Group Participation Rubric
  4. Experiment Rubric .

EXTENSIONS:

  1. The students can design their own activity to help explain buoyancy or an aspect of buoyancy.
  2. Use these activities to move into more extensive research about floating objects, such as ships. Give the students the opportunity to design their own ship to see if they can float the ship.

REFERENCE LIST:

Challand, H.J. (Ph.D.) (1984). Activities in the physical sciences. Chicago: Children's Press. [ ISBN: 0-516-00504-9]

Elementary science experiments. (1971). Compton: Educational Insights.

[ISBN: 0-88679-352-1]

Schwaller, A.E. (1989). Transportation, energy, and power: technology. Albany: Delmar Publishers, Inc. [ISBN: 0-8273-3227-0]

Williams, J. (1992). Projects with water. Milwaukee: Gareth Stevens Publishing. [ISBN: 0-8368-0771-5]

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Read Aloud: The Voyage of Odysseus Lesson

Ship Making and Ship Regatta

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