Misconceptions in Science :
Paresh K Joshi
Homi Bhabha Centre for Science Education,
Tata Institute of Fundamental Research
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Plan of talk
What is a Misconception?
Experiences of interactions with teachers/students
Some examples.
Dealing with (mis)conceptions.
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What is Misconception?
Facts away from common perception
Sounding correct but misleading
Insufficient understanding with current
science
Outright erroneous
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Misconception?
Misconception is an erroneous conception; mistaken notion
(Dictionary.com).
Typical errors come when students are confused about the limits of
applicability of ideas or similes or have incomplete information.
If not corrected early, these misconceptions can end up with internally
inconsistent picture of scientific perspective of the nature.
Often science fiction plays crucial role in strengthening these “ideas”.
Students tend to build upon these erroneous ideas and move in a wrong
direction
It can eventually drive students away from science.
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SCIENCE FICTION
Black holes and LHC experiment
HONEY I SHRUNK THE KIDS
GOLDEN COMPAS
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How to deal with them
Some of the concepts can be refined/clarified by using experiments or
demonstrations.
Some by thought experiment followed by theoretical equations to lead to
some qualitative explanation
Computer simulation/animation/diagrams
Drawings to the scale
Logical arguments with analogies
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PERPETUAL MACHINE
Most attractive topic
Students tend to get carried away due to unclear understanding
of concepts
If teachers do not stop these ideas, such misconcepts get boost
Need to explain the students/teachers proper
concepts, allow them to try it out, collect
statistics/data etc
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Power source -> two DC motors
-> Gear system
-> Another 2 DC motors (generators)
CLAIM
More power generated than the input power
Collection of data is the eye-opener
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PROBLEM : MOIST AIR IS HEAVIER/LIGHTER THAN DRY AIR
Common conclusion : air with moisture has to be heavier than
air without moisture
My effort : Carry out simulation.
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O2
N2
CO2
H2
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Oxygen and Nitrogen together make up more than 90% of
atmosphere
So on average the total weight of unit volume reduces with
introduction of water molecule
Hence moist air is lighter than dry air.
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PROBLEM : ICE SKATES MELT THE ICE ON SURFACE BY PRESSURE
Common explanation : pressure lowers the melting point of ice
resulting in thin layer of water, allowing skater to skate
Problem with explanation : It can be shown theoretically that the
pressure applied is not sufficient to melt the ice
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Ice melts under pressure?
dP/dT = L/TDV
L=latent heat of water = 330 kJ/Kg
DV = change in volume of water. 1kg of water freezes to make 1.1 lt of ice i.e. .1
lt = 100 cm3 = 100 x 10-6 m3 per kg = 10-4 m3/kg
T = 273 oK
If a human weights 100 kg, Force of 1000N
area of contact; (50 mm length, 2mm width) 100 mm2
pressure is 1000N/100 mm2 = 1000N/.01 m2 = 107 N/m2 = 107 Pa
dT = (107 ) x (273) x (10-4)/(330 x 103)= 0.83 oK
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As per Wikepedia, for the ice skating arenas, where the ice is maintained at -
7oC, we would require almost a ton of weight to melt the ice.
Pressure effects melting point. BUT ice will melt only if close to 0oC
A claim : A wire and two weights on ice cube. But the melting is due to “hotter”
wire due to surrounding
The reduction of friction is due to liquid water which is few molecules thick
Conclusion : the real reason is deeper than just the pressure effects. Experiment
in planning stage.
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PROBLEM: FEEL FOR DIMENSIONS OF SOLAR SYSTEM AND ATOMS
This results in students having several ideas about earth and solar
system which are untrue
The lack of feeling for dimensions leads to unphysical concepts in the
mind of the students. This has been seen very regularly in science
exhibitions
Launch of satellite which can LIGTH UP NORTH POLE IN WINTER!!
My effort : To explain the atomic and solar systems to the scale (to the
best of my abilities)
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Conclusion
Students have plenty of misconceptions due to
insufficient understanding of ideas. This may
arise due to unsatisfactory explanation or
confusion in comprehension due to lack of
attention.
Students need to be made aware of as clearer
concepts as possible
This will help curtail students going further in
science with as consistent picture as possible
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Students at Olympiad level were tested.
Number of students who were asked this question: 205
Number who answered correctly : 98
More than half could not “see” the fallacy in fiction
Number, who answered wrong : 70
Those who did not attempt : 37
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Examples in Biology: Photosynthesis is a one step process (from World Applied Sciences
Journal 3, p283 (2008))
Current explanation: indicates as one step process
Photosynthesis in day, respiration in night
Humans give out carbon-dioxide, plants give out oxygen
Sunlight is used for many other processes besides mixing water with carbon-dioxide to
produce glucose. These are also called PHOTOSYNTHESIS
Besides chlorophyll, some other enzymes and organic compounds are also required for
the generation of glucose
Glucose produced is not “free” glucose but part of several products?
Conclusion: The current explanation needs to be amended with appropriate additions.
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Misconceptions of children
Flow of charges in AC and DC
Flow of charges on the surface of conductors
Most of the textbooks talk of flow of current from positive to
negative terminal. It is actually flow of charge.
Ben Franklin’s kite was struck by lightening?
Any quantity can be measured as accurately as one wants e.g.
you can infinitely magnify a picture to see an atom!
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Relativistic Concepts
What we see in space is not from “now’’
Things are not “simultaneous’’
Time flows at “same rate’’ in range of our
perception. But is it true throughout the
Universe?
???????? What’s next?
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Thank You
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