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Buoyancy Unit

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Learner Outcome Content Learning Strategy

Establish prior knowledge.




What makes an object sink or float?

Develop class charts of "Things We Know About Buoyancy" and
"Things We Want To Know About Buoyancy".

Review properties of objects.



Predict and test for buoyancy.

organizing data in a chart


Activity 1:
What things sink and what things float?
How are these groups the same or different?

Record in Science Journal:
What properties might effect the buoyancy of an object?

Weight when combined with volume is a factor in determining buoyancy.




Activity 2:
Predicting and testing buoyancy of objects when weight is the only variable.

Clay balls of specific amounts can be made to float or sink. Weight alone is not a factor in buoyancy.

Dividing clay and measuring equal amounts using a balance scale.

Activity 3:
Will objects with the same weight always have the same buoyancy? Use equivalent amounts of clay to make the clay sink and float. Record tests done and results.

Record in Science Journal:
Three things that will make a clay shape float or sink.

Clay boats can be designed to have different amounts of buoyancy.

surface area

Activity 4:
Design a boat that holds the largest number of tiles.

Who Sank the Boat?,
by Pamela Allen

Record in Science Journal:
Why is a chosen boat more buoyant than others.

Varied amounts of cargo can be held by boats. Does the size and shape of cargo effect the buoyancy?






Activity 5:
What factors determine the amount and type of cargo a boat will hold?

Research different types of ships and make a poster showing the shape of the boat/ship and the advantages of that type of ship.

Design boats which hold varied types of cargo.

The weight of the water displaced by a floating object is equal to the weight of the object. Objects that sink are heavier than the water they displace.


Activity 6:
How much water is displaced by objects of different weights but the same shape? How are displacement and buoyancy related?

Build a "sinker" and a "floater" that look the same.

Displacement is related to the shape of objects which have equivalent weights.

surface tension

Activity 7:
What volume of water is displaced by differently shaped boats?

Explain which of three objects is most buoyant and why.

When weight and material are kept the same, the design of a boat will determine the amount of cargo it can hold.


Activity 8:
Design boats made from aluminum foil to carry a variety of cargo: pennies, beans, and craft sticks. How will the design vary for the cargo?

Record in Science Journal:
Record 3 things that effect the type of cargo a boat can carry.

Liquids have different properties, including density. The density of the liquid will affect the buoyancy of an object.

Activity 9, Part 1:
Determine density of liquids through weighting equal amounts of each liquid. Observe properties of liquids.

Activity 9, Part 2:
Use identical acrylic beads to observe the differences in buoyancy based on the density of the liquid.

Conduct an experiment to determine the type of liquid in a vial.

The density of salt water is greater than that of fresh water. Objects are more buoyant in salt water.


Activity 10:
Students will prepare slat water according to specified ratios and compare each of the waters for buoyancy.

Conduct an experiment to determine the comparative density of each water sample.

Many variables affect the buoyancy of a boat.

Construct a boat using all natural materials (and string). The boat can be no larger than 15cm x 15cm. It should be able to hold a can of soda as cargo.