Science Conundrums
get them thinking
Introduction
Suggested implementation
The conundrums presented are intended as a recreational challenge for your students, not as an
assessment task. The scientific concepts contained in them are within the scope of primary science
education but most of the answers are counter-intuitive. Each conundrum is likely to stimulate lively
discussion in the classroom and at home.
Use the blackline masters
Blackline masters of each conundrum are available to download and photocopy. These will ensure
students don’t become confused about the questions and are able to share the conundrums at home.
Parents will love them too
Parents and guardians are likely to enjoy having a crack at these conundrums too and may be able to
provide you with more science and logic riddles to use.
Allow sufficient time
If possible, allow at least one week between setting the problem and due date for entries.
Make a Conundrum Box
Decorate a cardboard box with coloured paper and pictures from magazines for the prize draw but limit
the number of entries to one per student.
Mini-prizes
You can create a competitive environment by awarding prizes such as a mini-chocolate bar to the first
three or five correct entries drawn from the entry box. The remaining correct entries could receive a
smaller prize such as a sticker or lolly.
Discuss the answers and reward good thinking (not just right answers)
Discuss the answers and ask students how and why they arrived at their conclusions. You may
discover that students who did not reach the correct solution may have used a great deal of good
scientific reasoning.
Be honest about your first answers
If your first answer to a conundrum was wrong, letting your students know! This will help to create
a ‘safe’ learning environment in which students feel confident about making suggestions and
discussing ideas.
Surfing Scientist | Conundrums
© 2004, Ruben Meerman, ABC Science
Conundrum #1 Rock in a boat in a pool
This one stumped Robert Oppenheimer!
A small boat is floating in a pool. In the boat is a heavy rock.
What happens to the water level in the pool if the rock is thrown
overboard, into the pool? Will it rise, fall, or stay the same?
Suggestion for illustrating the “Rock, Boat, Pool” conundrum
How to demonstrate the solution:
You’ll need:
POOL:
Large clear plastic container (eg food container)
BOAT:
Smaller plastic container (eg margarine tub)
ROCK:
Rock or steel object *
Water
Food colouring
* choose a small heavy item that almost sinks the ‘boat’ but not quite - a big
wheel nut or the head of a hammer are perfect
Mark the water level on the side of the ‘pool’ while the rock is in the ‘boat’. Take the rock out of the ‘boat’,
drop it into the ‘pool’ and put the boat back. The water level will fall.
TIP: keep the rock centred in the boat so it doesn’t capsize – add some paper towel to stop the rock rolling
around
It’s counter intuitive … even top physicists get this wrong!
This problem is famous for stumping Robert Oppenheimer, one of most famous physicists of the 20th Century
and two of his physicist pals George Gamow and Felix Bloch. So if your first answer is wrong, don’t be afraid
to tell your class! You can demonstrate and prove the answer to the class with some plastic containers and a
rock.
Oppenheimer directed the Manhattan Project which led to the development of the first atomic bomb. After
seeing the first ever explosion of an atomic bomb in the New Mexico desert, he said ‘we knew the world
would not be the same’. He later opposed the development of an even more powerful hydrogen bomb.
After you have revealed the solution, reassure your students that most people (even some respected
physicists!) get this problem wrong because the most intuitive answer is the wrong one.
Key concepts:
Floating and sinking / Density / Archimedes’ Principle / Buoyancy
Surfing Scientist | Conundrums
© 2004, Ruben Meerman, ABC Science
Surfing Scientist | Conundrums
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Student Answer Form - Blackline Master
© 2004, Ruben Meerman, ABC Science