Picnic Day

UC Davis Picnic Day is a giant open house attended by 50,000 or more
people. The Physics Club runs a "magic show" and a demo room where
visitors can do some hands-on experiments, but there hasn't been a
kid-friendly physics room in the past.  This year, I decided to make
one with the help of kids and parents at Peregrine School.  The day
before Picnic Day, I brought all my toys (Coriolis effect demo,
balloon in a bottle, infrared camera, mixing colors of light,
airzooka, etc) to the school and spent the morning training students
and parents so they would be able to explain the ideas behind them to
visitors on Picnic Day.  On Friday night my wonderful wife Vera and I
set the demos up in a room on campus, and on Saturday we had a ton of
visitors.

I think we did a really good thing here.  We didn't have our kids
explaining physics to other kids as much as I had imagined, for
various reasons: our kids were having fun playing too; they wanted to
visit other exhibits on Picnic Day; and most of the visitors to our
room were actually adults.  So the kids got less practice in
explaining physics than I had imagined, but we did a great public
service.  As an educator, I'm always thinking about ways to tweak
things, so if there is a next time (or as advice to others thinking
about doing this kind of thing), one way to get kids really deeply
invested might be to have them develop their own unique demos.

A Sense of Scale

Today we covered three small topics.  It's my last day with the 1-2
graders (I will rotate to the upper graders), and also the last day
before Christmas vacation, so I tried to squeeze in several fun things
and also answer some of the questions which arose last week.  So we
didn't go super-deep in any one topic, but we had a blast. 

We started with a movie: the ten-minute 1977 classic Powers of Ten by
Charles and Ray Eames.  I wanted to show this movie because the kids
had many questions last time, when I mentioned galaxies but didn't
have time to really explain them.  This movie steadily zooms out from
a person on Earth to show how big and how far apart astronomical
objects are.  The movie then zooms progressively in to show the sizes
of microscopic things.  (Note: if you want more snazzy modern special
effects you might try the more recent Cosmic Voyage, but Powers of Ten
feels more intense.)  I stopped the movie many times to answer
questions as they arose, but eventually there were too many questions.
We had four 3-4 graders in the room, and I will be doing astronomy
with them in the spring.  It looks like showing this movie would be a
good way to start my three months with them.  They could generate
questions, and we could take our time answering them.  The best
question today was, "How do we know all this?" and I hated not having
time to give a real answer.  My three months of astronomy with the 3-4
graders will be the answer to "How do we know all this?"

I then showed a website for visualizing the sizes of things, where you
control the zoom. This is a great site for showing how much
bigger the Sun is compared to Earth, how much bigger some stars are
compared to the Sun, etc.  But be warned: they do NOT show the space between these objects, so don't be fooled.  The space in between stars
is VERY, VERY BIG compared to the stars themselves. 
Apart from that, it's a great tool.  (One caveat: I did not zoom out all the way to the "estimated size of the universe"...there is no estimated size of the universe.)  Exploring this site also generated many questions, so that may also be a good icebreaking activity.  Because you can zoom in as well, it could even be a good icebreaker for life sciences as well.

A few more links for interested parents:

• http://www.nikon.com/about/feelnikon/universcale/  is a similar idea as the previous link but with a different feel.  It's worth checking out, but it mostly focuses on microscopic things rather than astronomical things (it has a few mistakes too.

• http://www.wordwizz.com/pwrsof10.htm is another site along these lines; it's not as pretty as the previous two, but it does properly show the vast space between things.

• http://www.powersof10.com/ is a site (currently in beta) by the Eames Office. I just discovered while gathering links for this post, so I can't say much about it other than it looks promising.

Activity number two was understanding orbits with a donutapult demo and play with the coin funnel.  Since I've blogged about this before, I won't describe it in detail here.  If you'd like to read about it, search for these terms (donutapult and coin funnel) in this blog's search box.

Activity number three will be the next blog post.

Origins Part II

(This is a continuation of a previous post.)

After a short break, we tackled the Big Bang.  I asked if we needed to
extend the timeline even further back than the origin of the Earth.
They were clear on the need to do so, since the Earth and the solar
system formed from a pre-existing cloud of gas.  I showed them some
pictures of galaxies and then some of a fly-through movie of galaxies from
the Sloan Digital Sky Survey.  I just wanted to roughly establish that
galaxies are like neighborhoods: we have ours, and we can see where
some others are too.  It was clear later that they have no real idea
that galaxies are much bigger than the solar system (even though I
said it); they kept mixing up planets and galaxies.  But I didn't
dwell on that; I figure there's only so much I can do in one morning,
and it was more important to establish that "things are moving apart"
than to work on a sense of scale.

Next, I took a long loose spring (almost like the helical telephone
cord that used to be on all landline phones) to which I had attached
galaxies (each galaxy had the name of a kid).  Starting with the
spring scrunched up, I extended the spring 12 feet or so and got the
galaxies far apart.  I did this a few times so they could see how all
galaxies moved away from each other.  This was actually the first time
I had done this demo, and now I'm sure I will do it with my college
kids.  I always use a balloon, and I still will, but there's something
nice about also doing the one-dimensional case.  It just makes
everything a lot more visible, especially in a big room.  With the
spring stretched I asked how we could figure out how long it has been
since everything was together.  One kid figured it out right away.  He
explained that knowing how fast they are moving and how far apart they
are, we can calculate the time it took.  He used the example of a
speed of one inch per year.  In that case, the number of inches apart
is the number of years it took to get that far apart.  This was an
amazingly good answer; it was almost as if I had rehearsed it with him
beforehand and planted him in the audience (I swear I didn't).

Next we went outside and practiced doing the same thing with our
bodies.  With Teacher Pa as the Milky Way, we all ran away from her.
Teacher Ethan ran the fastest and became the most distant galaxy by
the time I said stop.  I wanted to make clear that the most distant
galaxy is further away not because it has been traveling for a longer
time, and that there was a time when all galaxies were together.  We
went back inside and I drew a diagram of us as someone above the field
would have seen us.  If that person came upon that scene and saw us
moving very slowly, would he guess that we had started a long time
ago, or a short time ago?  (Long.)  If that person came upon that
scene and saw us moving very quickly, would he guess that we had
started a long time ago, or a short time ago? (Short.)  Using the same
logic, astronomers have found that all galaxies were together and
started moving apart (the Big Bang) 13.7 billion years ago.  I made a
big show of extending the timeline into the hallway and out of the
school to emphasize that that is a long time.

Now, the kids may have gotten the wrong impression that we are at the
center because everything is expanding away from us.  To combat that,
I had prepared two transparencies.  One has a smattering of galaxies, each
with a different shape so that it's recognizable.  I had prepared this by putting
graph paper behind the transparency and drawing galaxies at random coordinates.
I prepared the second one by drawing the same galaxies (now in red instead
of black) at the same coordinates multiplied by 1.5.  You can pick one galaxy
in the middle to represent the Milky Way and show the initial (black) transparency
to show where the other galaxies are around it.  Then overlay the red one, matching
up the Milky Way's position, to see how everything moved away from us.  Here's the
cool part: now you pretend you are an alien in another galaxy, match up that galaxy
across the two transparencies, and you ALSO see that everything is expanding away
from the alien!  This blew everyone's mind, including the teachers.  We spent a fair
amount of time with the kids picking a galaxy, and me matching that galaxy and
showing that everything moved away from it.  Bottom line: just because we
observe everything moving away from us doesn't mean we're at the center.  When
there's more space  everywhere, EVERY galaxy can observe this.  We're not special.
People often ask, where did the Big Bang happen?  It happened everywhere,
including here!  All the places that all the aliens in the universe could call "here"
all overlapped , in the distant past, with what WE call "here"!  I reinforced this with
the traditional balloon demo of the expanding universe: draw some dots on a partially inflated balloon, then fully inflate it and show how each dot is further from each other dot, but none is in a special or central position.  If the balloon could really be completely collapsed, then all the dots would be in the same starting position without ever really moving away from its position on the balloon.

But, should we believe that we can extrapolate that far back in time?
We should look for evidence! I made a lame show of demonstrating how
things are hot when compressed (I brandished a bike pump and asked
them to notice how the valve gets hot next time they pump up a tire),
so that the whole universe would have been red hot at some point in
the past when it was highly compressed.  We actually see that light:
it's called the cosmic microwave background.  This is fossil evidence
of a hot early universe.

We were running out of time but the kids voted to do the marshmallow
activity rather than just stop early.  I had brought white and yellow
mini marshmallows and toothpicks.  These represent the building blocks
of atoms (technically, protons and neutrons, but I didn't use those
words).  These building blocks can be stuck together only at very,
very high temperatures which the universe experienced only in the
first three minutes, when it was even hotter than red hot.  (Kind of
like marshmallows will stick together if heated.)  We had talked about
solids, liquids, and gases in previous weeks, so I sketched out
hydrogen (just one proton) and helium (two protons and two neutrons),
which they knew were gases.  I had set up cups half full of a mix of
protons and neutrons, in a 7:1 ratio.  I gave them the cups and told
them they had only three minutes to build as much helium (ie stick two
white and two yellows on a toothpick) as they could.  Because of the
paucity of neutrons, they were typically able to build only 3 helium
atoms, with about 36 hydrogen atoms left over.  This is actually the
ratio we observe!  So the atoms themselves are additional fossil
evidence of a very hot early universe.  [Parents: if you're curious
where the 7:1 ratio came from, that came from the even hotter
conditions in the first fraction of a second, and the observed ratio
agrees with the Big Bang model, thus providing even further fossil
evidence. If you want to read more, search "Big Bang nucleosynthesis."]

Overall, it was a VERY successful day.  The kids had many additional
questions about planets and orbits which I didn't take time to answer,
and this could form the basis of an activity for my next visit, and I
do think they gained an appreciation of the basic idea that we can
tell the age of the universe from how fast it's expanding.  How well
they'll remember that or be able to answer questions on an assessment,
I'm not confident.  But the basic idea is not beyond the grasp of 1st
and second graders.  The movie we saw before the break was great, the
spring demo was great, and the marshmallow activity was good.  (We
didn't have enough time to do it really well, but it's a very
promising idea and I will develop it further.  Given more time, I
would have the kids make mini posters with "raw ingredients" "elements
after cooking in the heat of the Big Bang.")  The radioisotope dating with
dominoes (see previous post) came up a bit lame, but I think it's a good idea
that just needs more refinement.

As the kids went to lunch, I worked on the science section of Teacher
Pa's poster comparing different religions' creation stories.  Because
I wanted to emphasize the LACK of parallelism as discussed in my
previous post, I ripped off the science column and posted it on the
wall next to the window where the religion part of the poster was.  I
also did not carry over the formatting of the rows in the religion
column.  I hope to post a picture here rather than describe it in
words, but I think I achieved the right balance in emphasizing how
science is different from religion while respecting both.

Update: if you look at this picture full size, you will be able to read the poster.

Origins Part I

Teacher Pa's class as been studying various religions, including their
creation stories, this week, so she asked me to review the scientific
"creation story" with the kids.  She had made a big poster with
Hinduism, Judaism, Christianity, and Islam as column headings, each
with entries in rows titled [Name of] God, [Sacred] Book, Creation
Story, Golden Rule, What Happens After Death, and Holidays, and she
wanted me to fill in a Science column for Creation Story, Golden Rule,
and What Happens After Death.

I wanted to make very, VERY clear to the kids that science is not
another religion, so I refused to tell a "creation story" and instead
made a detective story about our origins.  (It turns out I was
justified: even after spending the whole morning with the kids and
emphasizing how science works, as the kids went to lunch I began
ripping the Science column off the religion poster and my own son
Linus said, "Dad, what holidays does science celebrate?")

I started the morning by discussing what kinds of questions science
can answer and what kinds of questions it can't.  If you're about to
bite into your last cookie and someone asks you to share it, can
science help you figure out if you should share it?  No.  If your best
friend moves away and you're lonely, can science help you figure out
what to do?  No.  Religion might help you with those questions.  But
if you have a question about nature, such as "When did the Earth
begin?", then science can help.  I think it's super-important to help
kids draw these distinctions.  Because religion tries to say something
about our origins, and so does science, it's tempting to make
parallels between them.  But the differences are more important then
the superficial parallels, and we need to help kids see that.  Science
and religion are simply about different things.  If we had a poster
comparing different sports, we wouldn't put Sudoku on it!

The kids had done a timeline of the history of Davis, so I started
with a blank timeline with "Now" on the right and "?" on the left.  I
put a few recent events (the years they were born) close to "Now" and
asked how we could know about the distant past using evidence (clues).
Because they had recently been to Yosemite and seen a slice of a tree
with about 1,000 rings, I started with that: we know that trees grow
one ring each year, so this tree tells us that Earth is at least 1,000
years old.  In fact, the oldest trees in the world live in California
and they are over 4,000 years old, so I marked that too.  (Aside: by
matching long-dead trees with just-felled trees [using ring thickness
as an indicator of how good for growth each year was], scientists have
been able to put together tree-ring histories going back about 10,000
years!)

Next, we moved on to rocks. They had studied some geology in
preparation for Yosemite, so we reviewed how long it takes millions of
years for a river to carve a canyon, based on how fast we observe it
carving today.  So Earth is at least millions of years old.  One kid
knew that some rocks are at least 1,000,000,000 (one billion...I wrote
out the number to impress them) years old.  But how, I asked.
"Dating."  OK, but how do we do that?  I did a very simplified version
of radioisotope dating.  I took some dominoes and stood them up on a
desk.  Standing up, they have some potential energy, because they have
the potential to fall.  Once fallen, they don't have potential energy.
(We had talked a bit about this concept previously.)  Now some atoms
in your bones (or in rocks) have this extra potential energy, but as
time goes on more and more of them lose this.  I knocked down a few to
illustrate the passage of some time, then a few more to illustrate the
passage of more time, etc.  They quickly got the idea of "more down
equals older" (I gave them many scenarios and they got the relative
ages right) but I'm not sure what they were really visualizing when we
said "more energy" or "fall down" because I got questions about
whether the atoms are dead or had changed into something else.  A nice
thing about these dominoes was that they came in different colors, so
it was easy to point out that this domino is still a red domino with 5
and 2 dots, it's just that it doesn't have extra energy now.  So I
think the got the idea that we were using small particles in the rocks
as a clock, but not much else.  Which is probably ok; you can't do
everything.  (If I had planned this whole semester better I probably
would have brought in a microscope very early on, and established the
concept of atoms so that I could safely refer to it throughout the
semester...last year all the kids in the school studied atoms but only
one of those kids is in this room this year.)

So I extended the timeline all the way across the other (very long)
whiteboard and wrote 4,500,000,000 as the age of the oldest rocks on
Earth.  I then mentioned meteors, which they had heard of, and how
their slamming together would generate heat.  (I slammed clay lumps
together for visual effect.)  We think Earth was formed by meteors
slamming together and creating so much heat that they melted together.
The rock-dating clock starts when the rock solidifies, so the age of
the Earth is 4,500,000,000 years.  I then wanted to show them a movie
rendering of this process, and I showed the first few minutes of the
Birth of the Earth episode of How the Earth Was Made; in the first
several minutes they have some really nice visualizations of this.
But they like it so much that we kept watching, well into break time,
and almost finished.  But with about 10 minutes left in the 43-minute
episode, I really wanted them to stretch their legs so we encourage
them to go outside but left the option of continuing to watch. Half
the kids watched to the end.  I highly recommend this episode, and in
fact this whole series.  It emphasizes the use of evidence to test
ideas.

The kids had MANY questions in response to the video.  It was great to click Pause as soon as a question arose so I could deal with it right away.  I felt like the movie was an awesome way to keep their attention (which is sometimes a struggle), but I could still provide an interactive teaching environment.  It was the best of both worlds.




I have a lot more to say about what we did after break, but I'll make
that another post.  To be continued....

Written in Fire

We split Friday morning into two unrelated activities: sound, and a
review of states of matter.

For sound, I brought a lot of toys: tuning forks, a xylophone, etc.
The standard I wanted to cover was "sound is made by vibrating objects
and can be described by its pitch and volume" so I started with the
tuning forks and steered a discussion of pitch and volume (they
noticed right away that the tuning fork vibrated).  It was pretty
funny, as the kids focused entirely on pitch, and I could not get them
to guess, despite numerous hints, that VOLUME or LOUDNESS was a
difference between the two sounds I was playing, even when they were
the same pitch.  (It didn't help that when I really whacked the
xylophone hard, it did change its pitch somewhat as the whole thing
shook.)

Then I turned the kids loose to play with the tuning forks, the
xylophone, and a few other toys:

• bathtub flutes, which you can fill with water and then blow on while they drain.  The pitch corresponds (inversely) to the length of the wave which just fits in the air-filled part of the tube, so the pitch starts out high and then drops as the water level drops.

• plastic hoses flared on one end.  You whirl them around quickly, and they make an eerie whistling noise.  Same principle as the flute, only this time the length is fixed, and we make the air flow by whirling the tube rather than blowing on it.

• a "thunder stick" which is a long spring connected to a drum membrane stretched over one end of a tube (the other end is open).  Holding the tube and shaking it results in surprisingly loud boingy sounds.

Then we got back together as a group and talked about how our
observations are explained by sound being a wave.  To visualize this,
Teacher Pa and I stretched a very long spring (like the coiled wire
that ran from a telephone to its handset, in the old days before
wireless phones) across the room, and I bunched up my end and released
the bunch (still holding my end).  It was very clear that a pulse
traveled the length of the spring to Teacher Pa, and it bounced off
her and came back to me.  I related this to the behavior of the
thunder stick (what do you think happens if you hold the spring rather
than the tube?)  We also had two plastic cups linked by a string, and
Teacher Pa gave a chance for each kid to hear her voice carried along
by the string.

For the piece de resistance I brought a Rubens tube.  This is a long
tube with many small holes drilled in a line, connected to a propane
tank.  You turn the propane on and light the holes so it looks like a
row of 100 candles.  Now comes the cool part: there is a speaker
attached to one one.  Hooking it up so that music plays on the speaker
makes waves in the propane in the tube and pushes it out more in some
places than in others.  The fire dances to the music!  Music has lots
of tones mixed together though, so it's best to start with some pure
tones.  I brought a function generator to generate tones of any
desired frequency and amplitude, which is a really great
visualization.  Into and beyond break/snack time, kids and teachers
from all the rooms in the school were cycling through our room and
watching this.  The upper graders were transfixed.  They wanted to try
all their favorite songs.  We found that (to the dismay of some)
Gangnam Style was a really good one for making the flames dance.  We
eventually had to shut it down at close to 11:30, about an hour after
I first fired it up.  To see a Rubens tube in action yourself, check out this educational video.

From 11:30 to 12:15, Teacher Pa led us through some activities
reviewing the states of matter.  For example, she passed out images of
many different things and the kids had to paste them onto a poster in
the Solid column, the Liquid Column, or the Gas column.  This was
really useful for the kids, and for the teachers to assess how much
the kids got it.  In discussing this with the kids, we found a great
idea for next week: clarifying what we mean by "amount" or "size" of
something.  The difference between "size" (which most people would
take to mean a diameter, a distance across, or a height) and volume
came up in the context of gas expanding to fill its container, and it
was clear that we didn't have time to address it that day.  So we'll
do that next time.  It will play into one of the Investigation and
Experimentation standards about measuring length and volume, but I
want to keep it conceptually rich as I did last year.

It's a Gas

Last Friday I discussed solids, liquids and gases with the 1-2
graders.  I brought in samples of each to provide a basis for
discussion.  In addition to the obvious (a wood block, a glass of
water, a balloon filled with air), I brought some things designed to
stimulate their thinking: a rubber band, a cloth, a balloon filled
with water, and sand.  We took about 35 minutes to discuss how we
could define solid, liquid, and gas.  It's not as obvious as you might
think at first; for example, if liquids and gases flow unlike solids,
why can you pour sand?  Does that mean sand is a liquid?  I wish I had
time to document our discussion here!  I'll just document that at the
end it is important to note that substances can change from one state
to another and back depending on the temperature.  Water is the best
example: we talked about glaciers, lakes and rivers, and rain, which
they have already studied this year.  But it's worth mentioning other
examples lest they think this is peculiar to water.  The metal parts
of their desks were once liquid, which was poured into a mold.

In the hour after snack break, we did a more extensive experiment.  I
handed out cups with (small amounts of) vinegar, and they wrote down
observations: it smells funny, it's liquid, etc.  They did the same
with cups of (small amounts of) baking soda.  They also weighed both
cups on the scale together.  I found it easier to use a kitchen scale
which read grams rather than a scientific scale which reads to a
hundredth of a gram, so that I didn't have to explain decimal points.
Then they mixed the two and observed the reaction.  They drew it and
wrote down their observations.  Then we observed what was left: it
smelled different, and it weighed less (typically by a few grams out
of about 100 to start with).  We figured out together where the
missing grams went: when the bubbles popped, the gas escaped (in the
earlier session we had talked about this with respect to balloons).

They did all of the above in small groups (individuals, actually,
because we had three adults and four kids!), but we spent a few
minutes at the end summarizing what we learned.  One child wrote on
his worksheet "V [vinegar] +B [baking soda] = air" so that was a great
place to start discussing.  Did we know that gas was air?  What else
was produced?  They seemed to not recognize that what was left in the
cup was also a result of the reaction and should go on the right hand
side of the equation.  Is the stuff left in the cup just leftover
vinegar and baking soda?  No, because it smelled different.  The
equation written by the child was a great insight, but by the end we
produced a more accurate equation with more words.

Finally, it is important to note that this is a chemical reaction: we produced
some new kinds of substances! This is very much unlike water going
from liquid to gas, which they might have in mind as a model
transformation of a substance.  Because some of them like explosions,
I related it to the chemical reactions in explosions.  Explosions (ok,
most explosions) are chemical reactions too; they just happen faster
and give off more heat.

Then the kids spent 5-10 minutes drawing a scene with as many
different solids, liquids, and gases as they could think of, labeling
each.  At the very end, I rewarded them with a show of Diet Coke and
Mentos fountains.  It was raining, so I bought 1-liter bottles whose
fountains could be contained in the sink.  This turned out to be a
great capstone for the morning, as carbonation seemed to be a new idea
to many of the kids.  We tasted the Diet Coke before and after
defizzing to see the effect of gas on our taste buds.  We also
discussed how the gas was in the liquid and normally comes out slowly
(you can see small bubbles coming out when the cap is off) but comes
out quickly with the help of Mentos.

For those who want more: Here is an entertaining video of Diet Coke and
Mentos reactions.  If you want to go beyond entertainment and learn more
about why it happens, you should watch the Mythbusters episode on Diet
Coke and Mentos.  They do experiments with different ingredients to figure
out what is most responsible for the reaction.

Balance, and floating vs sinking

Today in the 1-2 grade room we had a blast with some of the ideas we
need to use in making the water feature.

First, balance.  I brought in two-meter-long sticks on pivots, along
with sets of weights of various sizes, and had the kids hang weights
in different places and then see where they had to place other weights
to balance it out.  They quickly discovered that a small weight can
balance a large one, IF it is placed at the end of a long arm.  This
was a really good exercise because, in contrast to some of our
previous ones, I had enough equipment for each child to explore
completely on his/her own. 

The pre-snack period culminated with two capstone events:
(1) I gave the kids a worksheet in which I drew balance beams
with a weight on one side (varying the size and position of the
weight), and they had to draw the weight (size and position) they
would put on the other side.  Mostly they got it right, and in the few
cases where there was confusion we had the equipment right there to
check if their drawing represented reality.  (2) I demonstrated how
balance facilitates rotation.  You can see a video I made about this
demo at the end of this blog post from last year.  As kids went to break,
some of them commented how this demo is like the Moon going around the
Earth, and asking whether the Earth wobbles a little as it does so.
The answer is yes, and so does the Sun as the planets (Jupiter has the
biggest effect) go around it.  Therefore, if you saw a star which was
wobbling, what could you conclude about it?  Right, it has planets!
This is really how astronomers do it; the vast majority of planets are
too faint to see directly given the glare of their host stars.

Post-snack, we switched to fluid mechanics.  We started by reviewing
what we learned about pressure last time, focusing on why water
doesn't fall from a straw when you cover the top with your finger.  I
then showed the same idea in slightly different form: with two 2-liter
soda bottles screwed together, water does NOT fall from the top one to
the bottom one (it may drip, but it doesn't make the waterfall you
might expect in an open-bottle situation).  The water doesn't fall
because for the water to go down, the air in the bottom bottle has to
move up, and the two get in each other's way.  We then figured out how
to make them not get in each other's way: swirl it to make a "tornado
in a bottle."  The air goes up through the middle while the water
swirls down around the outside.

We then took some time for each kid to make his/her own tornado in a
bottle, with the option of coloring and/or glittering the water.  This
was great fun; the kids were really into it and came up with some
pretty (and/or Halloweeny) combinations. 

Next, we studied floating and sinking, following more or less the
script from one of my Primaria sessions last year (adding a bit of
sophistication such as introducing the word density).  But we had time
only to get to the egg in the salt water.  We'll do the rest next time.

At the last minute, we stumbled into a nice connection between the egg
and geology.  Teacher Pa said that the way to tell if an egg has gone
bad is to see if it floats (in non-salted water).  Linus had said just
5-10 minutes before that pumice is a rock that floats because it has
lots of gas bubbles in it.  So the connection is that an egg which
floats (without the help of salt) probably has gas bubbles in it,
which clearly is a sign that it's going bad.

Hydrodynamics 101

Today I worked with the 1-2 graders to extend their concepts of force
and motion to include work and energy, and then, after the break,
fluid dynamics.

While waiting for the kids to come back from chorus to start science,
I sat with one child who hates chorus, and we interleaved the pages of
two phone books.  When science started, we talked about friction and I
used the phone books as a demo.  The friction of 200 pages trying to
slide past 200 other pages is so much that two strong adults cannot
bull the books apart.  Mythbusters had a great episode on this, in
which they used bigger (800 page?) phone books and couldn't pull them
apart even with cars.  They finally resorted to military tanks, and
found that it took a force of 8,000 pounds to separate the books!

We then talked about work, which is applying a force over some
distance.  Sitting in your chair, you are applying a force (your
weight) to the seat of the chair, but you are not doing work.
Exerting a large force (eg lifting a heavy weight) over a large
distance makes for a lot of work.  We related this to irrigation
because the kids are studying the community, and are about to learn
that farming really took off around here when large pumps became
available to move the water.

Energy is the ability to do work, and we spent a looong time talking
about different forms of (mostly stored) energy: food, chemicals,
light, heat, electricity, etc.  We spent a loooong time figuring out
what makes the electricity that comes to our houses!

Then came break.  After break we finished up a few more forms of
storing energy: magnets, rubber bands, springs, etc.  But mostly we
moved on to discussing how water moves (fluid dynamics).  I did the
"three-hole can" demo (see paragraphs 3-4 of this post) to introduce
pressure and the relationship between pressure and water height.  Then
I did the finger-on-the-straw demo (paragraph 6 of that post) to show
that the air also exerts pressure.  Next was a siphon tank demo, to
show that air pressure can sometimes help quite a bit in moving water.
This demo did not work well, possibly because of a leak, so see this
video.  Finally, I did the balloon in a bottle demo (paragraphs 6-8 of
the post linked to above) which is very analogous to the
finger-on-the-straw demo but far more dramatic....I could see Teacher
Ethan do a double-take when he first saw it.

Then I led the kids through designing different water systems on the
whiteboard.  I supplied basic ideas such as water flowing into a
shovel on a pivot, and asked them to predict what would happen (when
the shovel fills with water, that end pivots down, dumping the water
out).  We went through a bunch of these ideas, and I made sure to lead
them to realize the need for a pump to cycle the water back from the
bottom to the top.  By this point they were very eager to start
drawing their own ideas, which played right into my plan.  We had a
great time making posters of our ideas.  In the last five minutes, I
unveiled the hydrodynamics kit which they will use in free-choice time
(or whenever Teacher Pa deems fit) to actually implement their ideas.

Overall, I think it went really well.  We discussed a lot of ideas,
without overwhelming the kids, and the poster-drawing session was both
fun and educational.

Understanding the gravity of the situation

Last Friday with the 1-2 graders we reviewed and extended our
observations of force and motion which we began two Fridays ago,
before the Yosemite trip.  Because it had been two weeks, we started
with quite a bit of review, which I did by asking the kids questions
rather than lecturing to them.  We observed the motion of a rolling
ball in order to change the context from last time (when we used a
hoverpuck or a marble shot out of a blowgun).

I had them observe and draw some motions.  This addressed California
Grade Two science standards 1a and 1b, as well as built the case for
the following argument.

By observing a ball thrown up in the air, we concluded that there is a
force on it even when I am not touching it, and that that force is
simply gravity.  I then repeated the donutapult demo to refresh their
thinking on how something goes in a circle only when there is a force
on it; if there is no force on it, it will go off in a straight line.
Then we talked about the Moon and how there must be a force on it
because it goes in a circle around the Earth.  That force is also
gravity!

(I think the following was too advanced, but we did discuss it.
Gravity always points to the center of the Earth.  One student is
going back to Korea soon, so I drew Davis and Korea on a globe and
showed how this must be the case.  Then I noted how the force on the
donut also points to the center of its "orbit" because that is the
only direction the string can pull.  So there is very strong reason to
think that the force on the Moon is Earth's gravity, the same force we
know and love, that makes things fall when we drop them! [Standard 1e])

After the break we discussed how to send forces in different
directions and in different amounts by using simple machines such as
levers, pulleys, and gears.  I had brought in the Gears!Gears!Gears!
toys earlier in the week, so they easily got the basic idea of this
standard (1d).  But I lost them    when I got into the details of
levers...they weren't able to predict where to place a lever and a
fulcrum to perform a given task, nor were they able to draw arrows
indicating the sizes of the forces at the different ends of the lever.
And I didn't really have the equipment handy to do real hands-on work
with that, so I may do this again this Friday with better equipment.

Newton's laws for 1-2 graders

Friday I spent an intensive morning with the 1-2 graders working on Newton's
laws.  The format was quite a contrast from last year when I had 20 minutes with
each of three mixed-age groups!  That was insanely rushed.  Still, I followed more
or less the same format as last year, with the hoverpucks, the donutapults, and the carts, so I won't rewrite all that here.  I added a few things, which I will describe here, but mostly we used the time (45 minutes before morning break and an hour after) by going a lot more slowly and thoroughly.

I knew it was going to be a long morning for them, with a lot of different things to
pay attention to, so I started with an overview.  I started by writing three goals on the board and we talked about what goals are.  I told them that if we accomplished all the goals they would get a present at the end.  The goals were:

• observe how things move
• make a model to explain these observations.  I phrased it this way because the previous time I had worked with them one-on-one, we made models of how the mystery tubes work.  I wanted to draw an explicit parallel: a few simple connections will explain and unify a whole lot of observations.
• figure out how to measure pushes and pulls (forces)

We did a lot of observations of the hoverpucks and the donutapult before break. One thing I could do better next time with this age group is let them play with the hoverpucks first, and then ask for their observations; that might be easier than holding their attention through some demos and then letting them play to build on that.  In any case, by break time we had figured out that objects don't change their speed or direction unless acted on by a force (note that friction is a nearly ubiquitous force, which always acts to slow things down), and the donutapult reinforced that.

After break, I brought out a new toy which I had made earlier in the week by softening a PVC pipe in boiling water and bending it into a circle (curving it around a bit more than one full loop so that it clearly has two ends).  A marble fits inside the pipe and I blow on it like a dart gun.  When the marble comes out, does it continue curving around that circle, go in a straight line, or something in between?  This was another really fun demo.  [Note that I spent two hours making the darn thing, because this was my first attempt at softening PVC, and I ruined two pots.  Dedicated teachers spend much, much more prep time than most people imagine!]

Then we turned to the carts as per last year's agenda.  A new ingredient I added here is the leafblower on a skateboard.  We can trust the leafblower to always push against the air with a constant force, so stacking the skateboard with different weights nicely demonstrates Newton's second law.  We also heard an interesting misconception from one child: that the leafblower/skateboard had to be near a wall to push off the wall.  So we discussed how to design an experiment to test that, and how the experiment showed that the leafblower pushes against the air, not the wall.

This completed the "make a model to explain these observations" goal: objects don't change their speed or direction unless acted on by a force (Newton's first law); a bigger force produces a bigger effect on a given object, and a given force produces a bigger effect on a lighter object than on a heavier object (Newton's first law).  These kids aren't really ready for a deep understanding of Newton's third law, so I summarized it as "things push back when you push on them."  That way of summarizing it may do more to prevent injuries than to improve their understanding of physics, but I felt that I was starting to lose them and that we should move on to our third goal.

The leafblower was indeed a nice segue to "figure out how to measure pushes and pulls" because when students pushed a heavy cart and then a light cart with the same force to observe the same pattern (a given force accelerates a light object more than a heavy object), they had some trouble really pushing with the same force on each cart.  Their muscles weren't very well calibrated.  So I asked how we could measure the size of a force.  I pointed to the scales we had used earlier, but this didn't generate any ideas other than "use a scale."  So I got a popsicle stick and showed that if I press on both ends lightly, it bends a little; if I press more it bends more; and if I press very hard, it breaks.  This is a rough way to measure force.

We can make it more precise by using a spring.  I hung a spring from the whiteboard tray and asked them what would happen if I hung a small weight on it, two small weights, etc.  (A weight is another thing we can trust to always pull [down] with the same force.)  I had taped a piece of blank paper hanging down from the whiteboard tray, and I used that to start to build up a scale with tickmarks and numbers.  Then we broke into two groups (I had only two springs) to construct two scales. Unfortunately, my group overloaded their spring and broke it rather quickly.  Note to self: bring more, and stronger, springs next time.  In any case, we did construct reasonable scales so they achieved their third goal and earned their reward: each child got a brand new, professionally manufactured spring scale.  Before they could play with them, Teacher Pa made them record some of what they had learned in their science journals.

I'd never done the "measuring force" activity before, and I think it went well.  The kids did play with the scales after recording in their journals, even a bit into recess time, so that was a good sign of engagement.  Linus and Malacha experimented with multiple springs set up in parallel and in series.  They observed, for example, that when two springs hold up a weight, each is extended only half as much as it is when it has to hold the same weight alone.  This is because each has to hold only half as much weight.

Some kids expressed interest in having a hoverpuck at home.  They are only $20 and are sold under the name Kick Dis.

Glaciers, Plate Tectonics, Rock Cycle and Fossils: The Geology and Yosemite

Friday was jam-packed with science this week as Teacher Carol and I
helped the upper graders demonstrate the geology of Yosemite to the
younger children, in preparation for our field trip there.  I stayed
in the 1-2 grade classroom, so I will mostly report from there.

Carol set up four half-hour activities:

• glaciers
• structure of the Earth (crust, mantle, core) and plate tectonics
• [snack/recess]
• the rock cycle
• making fossils

In each activity, the upper graders kicked it off by explaining the
topic with the aid of posters they had made (you can read more about
Carol's work preparing the upper graders on her blog).  The upper
graders knew their stuff but had not been trained in pedagogy, so
Teacher Marcia and I facilitated by asking questions and repeating
explanations with simpler words and examples when necessary.  (Teacher
Marcia was really excellent in this regard!  At some point after
discussing erosion, the movement of rocks came up again and instead of
assuming the students instantly made the connection to erosion, she
asked "Do rocks have legs?"  This was funny but also made the children
stop and make connections to what they had learned earlier.)  Then
each topic turned to a related hands-on activity or demonstration:

Glaciers: we went outside as the upper grades made a block of ice
slide down a "mountain" of sand in the sandbox.  The kids sketched it,
then returned in the afternoon to sketch it after the glacier melted.
The point was to observe the pile of soil and rock left at the point
of the glacier's farthest advance.  We will see moraines like this in
Yosemite.  Often, they serve as dams for rivers which form in the
channel left by the glacier, and thus have lakes right behind them.
This phenomenon of course wasn't visible in the sandbox demo but I
wonder if we could tweak the demo next time so that it is.
  
Structure of the Earth and plate tectonics: we used a hard-boiled egg
to demonstrate a really thin crust (the shell) over a mantle (the
white) and a core (the yolk).  The Earth's crust really is that thin
relative to its bulk!  Slicing the egg in half also fractured the
shell into "tectonic plates."  We further demonstrated different ways
in which plates interact at their edges (convergent, divergent, and
transform boundaries) with pieces of cardboard, paper, and our hands.

The rock cycle: we grated crayons to represent erosion, then we
deposited the grains into a riverbed of aluminum foil.  We did this
for a few different colors to make distinctive layers of sedimentary
rock, then we wrapped up the foil and added pressure (with kids'
hands) and heat (with a torch).  When we opened the foil we found
metamorphic rock!  The torch was my idea because kids love flame, but
it melted the outside without melting the inside, so I would recommend
Carol's original suggestion of a hot-water bath to supply the heat.

Making fossils: we transitioned from the rock cycle to this by
discussing how older layers of rock are deposited first and buried
further down, so we can relate the rock layers to the ages of fossils.
The 1-2 graders are really into dinosaurs, so this was a great
transition: training for dinosaur hunters.  Beforehand, Carol and I
half-filled small paper cups with clay and coated the flat top of the
clay with a bit of Vaseline.  The kids chose from a selection of
animal figurines and pressed their animal into the clay.  They removed
the animal to simulate the decay of the flesh, but the imprint
remained.  Then a mudslide came along (me pouring wet plaster from a
large cup) and buried the imprint.  They took the cups home and
excavated their fossils the next day.

It seemed like a great experience for the kids, but it would also have
been great if it had been a little more spread out, say over two
Friday mornings.  We were asking the 1-2 graders to absorb a lot of
information in one morning!  Teacher Marcia found a good way of
spreading it out after the fact: Carol provided worksheets for the
kids to fill out, but we didn't have time for that because we had to
go slower for the 1-2 graders, so Marcia decided she will use them to
reinforce and review over the next week.  Apparently the 3-4 graders
were able to complete their worksheets in the morning.

The upper graders certainly learned a lot in the week leading up to
this Friday, first learning from Carol (with the worksheets asking
them to articulate their knowledge), and then making posters and
rehearsing demonstrations to prepare for teaching the lower graders.
(If you want to read more about Carol's work with the upper graders,
see her blog.)  However, because the upper graders had no training in
instructive strategies (asking questions, asking students to come up
with additional examples, etc), the teachers in the room had to
intervene a lot (Carol confirmed that this happened in the 3-4 grade
room too) and by the end the upper graders had become somewhat
passive.  I wonder if we could improve this next time by asking the
upper graders to fill a more specific role rather than a general one,
for example each doing a certain experiment or demo which was
self-contained enough for them to feel expert in.  They were certainly
good in helping the kids one-on-one, for example in making the fossils
and, in the 3-4 grade room, in responding to questions asked by the
worksheets.

Mystery tubes 2012

This year I have a new title (scientist in residence) at Peregrine School, and a new format: every Friday morning with grades 1-2 for three months, then with grades 5-7 for three months, then grades 3-4 for three months.  This should allow me to go much further in depth with each group, and to facilitate really substantive projects on their part.  Today was my first day with the five first and second graders, and to break the ice I brought some "mystery tubes" which are basically like the one shown on this short video.

The students got their hands on the tubes, did any experiment they wanted to (short of looking inside the tubes), and drew what they thought was inside.  Most students went through a couple of iterations as they realized that their first model wouldn't reproduce their observations.  When a student was satisfied with his/her drawing, I brought out toilet paper tubes, strings, beads, etc so they could build a model and show that it behaved like the real thing.  The point: science is about building models (usually mental models rather than physical models), and this activity allows us to practice many aspects of this in one session, including thinking of experiments to test the model, performing those experiments, generating predictions from the model (hypothetico-deductive reasoning), and comparing the results of the experiments to predictions generated from the model.  Furthermore, since I never allowed them to look inside the tube we had ample opportunity to discuss how science is less about knowing the right answer than about the process of finding answers.  After all, nature never tells us the right answer directly.  Kids at this age are very much in the mode of gaining knowledge from books, but it is worth making them stop and think about how every bit of the knowledge in books was, at some point, figured out by someone who had to figure out by reasoning and then convince other people that it was correct. 

You can also read about the way I did this activity with mixed ages (grades 1-6) last year.   A note for teachers using this activity: it took much more time this year, 45 minutes, because the 1-2 graders did not have the fine motor skills to easily build their little toilet-paper-tube model with strings and beads.  With mixed ages last year, it seemed as if the young ones contributed equally intellectually, but the older ones probably did the actual tying of strings and beads.  And the 45 minutes was with two adults helping four kids!  If you try it with a larger group of 1-2 graders, you'll have to bring full-size materials. I do this activity with college students (who find it interesting and beneficial) so this activity is remarkable for the range of ages who find it suitable!

I learned something from Teacher Marcia too.  With five minutes remaining in the period, I wanted to have a wrap-up discussion with the kids.  She showed me a way to make kids pay full attention to the wrap-up discussion rather than surreptitiously keep working on their model: move them from the material-strewn desks over to the rug where they listen to stories etc.  This was brilliant.  Now if I can figure out how to do this with college students, I'll be set!