Will it float? - ABC

Lesson Plan 14

Will it float? Brief description Will it float is a surprisingly contagious, fascinating and fun game you can play everyday. Test whether mystery items sink or float daily over a week, fortnight or month in an aquarium or clear plastic tub. Use it as part of a unit on floating and sinking, or simply as a fun motivational activity. Each student can attempt to stump the class with a bizarre or mundane mystery item brought in from home. The class has a few moments to predict whether each item will float or sink and you can keep a tally of their successes. You could award prizes to students with the highest success rate at the end of the “Will it Float?” Season. Duration:

10 – 15 minutes per day (over a week, fortnight or month)

Year level:

Any

Topics:

Floating and sinking, Archimedes Principle, Density, Buoyancy

Preparation:

5 to 10 minutes

Extensions:

This activity is perfect for a unit on floating and sinking or simply as a motivational activity

Overview PER SESSION (total 10 – 15 minutes) 1. DISCUSSION AND PREDICTIONS

(5 – 10 min)

Introduce the mystery item to be tested and ask students to predict whether it will float or sink. Students can keep a record of their predictions in a science journal 2. TESTING MYSTERY ITEM

(5 min)

Place the mystery item in the aquarium to test if it floats 3. DISCUSSION OF RESULT AND OBSERVATIONS

(5 – 10 min)

Discuss the result and if students were surprised, why? Observe and discuss peculiarities about how the mystery item floats (eg on it’s side, vertically, at an angle)

Lesson 12 – Germination Experiment Page 1 © 2006 | ABC Science Online

Materials and equipment • • • • •

Aquarium / Clear plastic tub Water Assortment of objects (see below) Poster provided on page 6 & 7 Mystery items to test

Students attempt to stump the class with bizarre or mundane mystery items from home. Some suggestions for items to play “Will it float?”: Fruit Soft drink (diet / regular) Milk Can of beans Glue stick Yoghurt Chocolate bars Nuts Toothpaste Shampoo Cheese Small screw driver (plastic or wooden handle)

Will these items sink or float?

Preparation Bring in an aquarium and display in a suitable location, print out poster and stick to wall. Bring a few items to start the game. Students can then explore their house looking for mystery items to bring to class.


Objectives Students’ prior knowledge This activity is perfect during a unit on floating and sinking, Archimedes Principle or buoyancy, or simply as a daily analytical thinking activity.

Science skills Students will:

• • • •

Observe items before making predictions using sight Observe items before making predictions using touch Record their predictions in a science journal Infer the presence of an air bubble from the behaviour of an object

Science concepts • Substances which are less dense than water float (eg oil) while more dense substances sink (eg cheese) • Objects which sink displace their own volume of water • Objects which float displace their own weight of water • Air bubbles increase the buoyancy of a sealed object

Positive attitudes Students will

• Learn the distinction between a prediction and a guess • Learn to withhold judgment and assumptions until they have sufficient information to reach a conclusion • Be surprised at the difficulty in making simple predictions • Respect other people’s opinions and predictions (almost everyone will ‘predict’ correctly and incorrectly over the period the game is played) • handle equipment and water carefully and responsibly • dispose of waste responsibly (eg pour waste water onto plants or garden beds instead of down the sink)


Procedure PER SESSION (10 – 20 min total) Observation object, discuss and predict – Whole Class (5 – 10 min) • Introduce the mystery item to be tested / have student introduce the mystery item they have brought in from home. • Ask students to predict whether it will float or sink. Ask them to elaborate on their reasoning. • Initially, you might let students observe the objects by sight and later allow them to feel each one’s weight to help them make the distinction between a prediction and a guess. • As students become better at this, ask them to justify their predictions using appropriate language (eg density, buoyancy). • Students can record their predictions in a science journal

Test mystery item – Whole Class (5 min) • Place the mystery item in the aquarium

Discuss results and observations (5 – 10 min) • Discuss the result and if students were surprised, why? • Observe and discuss peculiarities about how the mystery item floats (eg on it’s side, vertically, at an angle) • Tally results

FINAL SESSION (5 – 10 min) • Tally results and award prizes to students with highest success rates


Teacher’s notes Why things float Substances A substance (eg oil, chocolate, styrofoam, wood) will float if it is less dense than water and sink if it is more dense than water. Objects An object will float if the volume of water it displaces weighs more than the object. An object will sink if the volume of water it displaces weighs less than the object.

Density and the standard kilogram The weight of the standard kilogram was originally based on the weight of 1 litre of pure water at 40C weighs ie 1L of H2O at 40C = 1 kilogram. The standard had some technical problems because water’s density changes with temperature, purity and pressure. The standard was replaced in 1889 by the International Bureau of Weights and Measures with the International Standard Kilogram Prototype. The prototype is a precise cylinder made of an alloy of platinum and iridium and is kept under controlled conditions in France. Copies of the prototype are kept as a reference in countries around the world.

Some examples Different varieties of fruit sink or float depending on their composition – the density of citrus fruit flesh and peel is significantly different so a surprising addition is to peel the fruit and test each separately.

Surprisingly, a can of diet soft drink floats while regular soft drinks sink. It’s due to the extraordinarily high sugar content of all regular soft drinks, which makes them more dense than the diet varieties.

Mayonnaise contains oil which floats on water. In a plastic squeeze bottle, it floats but what about the glass jar variety?


