a problem of scale
peter a’hearn
“i can see the molecules” -5 th grader peering into a test tube of water
“well you can’t because you’re old. I have really good eyes” -5 th grader when told he couldn’t possibly see molecules
“the test results shows the kids think the solar system and the universe are the same thing” “you mean they’re not?” -district level administrator
“there are positive and negative cells” -science teacher
“i am one cell” -high school biology student at the end of a unit on cells half the class agreed
“when i was a kid i didn’t believe in the solar system because when i looked in the sky i didn’t see anything that looked like the pictures in the books ” -elementary school teacher
“that is one atom of iron” -high school physical science Student looking at a beaker containing 55.85g of iron –one mole
just because they can give the right answer, doesn’t mean they get it
A Commonly Held Inaccurate Model of Teaching and Learning
as scales become bigger and smaller than those normally experienced, there is a tendency to lump objects into catergories of very big or very small -tretter, jones, and minogue 2006
experts and advanced students understand scale by unitizing- using new units when thinking in extreme scales- light years, nanometers, millions of years -tretter, jones, and minogue 2006
at your grade level, where do kids encounter extreme scales? big? small? in Space? in Time?
teaching kids about scale find out what they are thinking teach them to be critical of models put them in the picture help them figure it out for themselves use microscopes and telescopes
put the strips in order from the event that takes the shortest time to the event that takes the longest time
sun and earth 2
evaluate the model what is accurate about the model? what is inaccurate about the model?
Can you see a molecule with a magnifying glass?
meter- you
/10 meter
/100 meter
/1000 meter
/10,000m cell
/100,000 m
/1,000,000 m organelles and bacteria
/10,000,000 m- virus
/100,000,000 m macromolecule
/1,000,000,000 m molecule
/10,000,000,000 m- atom
how big is the giant? who thinks you are a cell? who thinks you are a molecule?
meter- you
meters
meters-soccer field
m- kilometer
,000 m –city the giant who thinks you are cell
,000 m
10 6 1,000,000 m- state
,000,000 m-hemisphere
,000,000m
10 9 1,000,000,000 meters Moon’s orbit The giant who thinks you’re an atom
at what scales do we teach kids about photosynthesis and respiration?
moon diameter 4000 km earth Diameter km earth to moon km step 1- change the units step 2- divide by 10s if that doesn’t nail it, try to divide or multiply by two.
try to add the sun! moon diameter 4000 km earth Diameter km earth to Moon km sun diameter km sun distance km
thank you peter a’hearn k-12 science specialist palm springs usd