The pre-K/K kids have been really interested in machines for a few
weeks now. When I first heard about that interest, I (with Linus's
permission) brought our set of Gears!Gears!Gears! to the room for a
long-term loan. Since then, I have seen kids playing with the gears
every morning I drop Linus off. When we saw a slightly more advanced
set of Gears!Gears!Gears! in Costco one Sunday (with different size
gears and a loop gear, plus some non-gear bells and whistles), it was
a no-brainer to buy that and bring that for a long-term loan as well.
The kids seem to really be into it.
So I thought of building on that interest by doing something with
pulleys, and I settled on building a simple elevator as an activity
which seemed doable, but still challenging enough to be interesting.
I borrowed a big old pulley from the physics department, brought some
of my own ropes and weights, and counted on the school having some big
dairy cartons and a decent place to hang the pulley.
After some looking around and testing, I settled on a certain tree
branch as a good place to hang the pulley, and I found a dairy carton
big enough for a kid to climb into. With the first group, I started
from scratch, asking them what they thought would be necessary to
build an elevator, and they suggested a basket (they even found one)
and rope (which I supplied). They needed a bit of prodding to suggest
a pulley, but they got that too after I suggested looking above my
head. Most of them didn't really know what a pulley was, so we
discussed that. I strung a rope through it and we each verified that
pulling down on one end of the rope made the other end go up. The kid
were really excited at this point! It was difficult for some of them
not to grab the rope, jump up and down, etc. I pointed out that one
advantage of the pulley is that the puller (the kids in this case, a
motor in real life) need not be on the roof to make the elevator work.
Then I attached the large milk carton and put some heavy object in it
for a first test. The more excited kids volunteered to pull on the
other end of the rope. They were able to lift the elevator, but it
was quite difficult; they had to recruit help and I think it was
successful only with four boys pulling at once. I warned them that if
they let go suddenly, the elevator would crash to the ground and hurt
the (imaginary) people in the elevator.
So I asked them to think about what could make the pulling and the
letting down easier and safer. They thought of all kinds of crazy
ideas before they spotted my weights. So I attached the
counterweights (in a small basket so we would adjust the amount of
counterweight) and we saw that the elevator was much easier to lift
and also easier and safer to let down. So then we were ready to give
rides.
The problem was that the dairy carton tilted too easily when lifted
off the ground, threatening to dump the passenger out. I tried to
stabilize it with additional ropes and by telling the passenger to balance,
but it never really worked. So starting with the second group, I
forbade rides. Instead, we used three containers full of sand to
represent three people. This was actually nice for the lesson because
I was able to put in just enough sand to balance the particular
counterweight I had; with a human passenger, the counterweight was a
help, but never really made it super easy to ascend and descend. With the fake
passengers matched to the counterweight, ascents and descents were very easy,
and I could tell the "motor" to let go, simulating a broken motor. The elevator
did not crash to the ground because it was attached to the just-right
counterweight.
So, once we got it going smoothly, I repeated these steps for each
kid: remove the counterweight; ask them to lift the passengers to the
top floor and have them discover how difficult that is; have them feel
how tricky the descent (from whatever point they reached) is; after
finishing the descent, add the counterweight and ask them to lift the
passengers to the top floor and see how easy it is this time; ask them
to let the passengers descend safely and feel how easy that is; ask the
motor to "break" and see how the passengers do not crash to the ground
because of the counterweight; finish the descent and start over with
another kid. I repeated this whole cycle about a million times
because many kids wanted to do it over and over! I was exhausted by
the end.
This was a pretty simple activity and the kids had a lot of fun. This
is a good lesson for me because I'm often tempted to think that a
potential activity is too simple and that I have to add a lot to it.
Simple can be good! If I ever try rides again, I need to experiment
beforehand how to make the elevator "car" tip-proof. But I think the
rides may have been a distraction. Each child was quite happy in the
"motor" role, so much that they wanted turns over and over, and of
course the motor role is the instructive one.
A small improvement would be to use two pulleys, to give some
horizontal space between the elevator car and the counterweight. One
thing which would take this to the next level would be to crank the
whole thing with some gears attached to a drum which winds up the
rope. I'll keep my eye out for surplus equipment which might be used
for this. And for a toy gear set with these kinds of pieces, which I
will then have to buy and put on long-term loan!
Saturday, October 29, 2011
Monday, October 24, 2011
We all learn with a little submarine
Friday I did the submarine activity at the elementary. This was at a
somewhat higher level because the kids here had been studying weight
and volume and how to measure them. Because I had told Lorie I would
be doing this activity, she sneaked in a lesson on density before my
visit. So I was able to discuss how density related to the
experiment. (What they remembered about density is that it's "weight
and volume together", but they were not able to articulate just how,
so this served as a good reinforcement.)
A few notes to myself on implementation: (1) the little rocks at
Lorie's house are great for shoveling in the bottles easily; (2) the
right kind of water container (low and flat) is really important,
because high walls and/or deep water is a big inconvenience; and (3)
don't let any kids fill their bottle with sand!
Overall, I'd say it worked just as well with the elementary as it did
with Primaria. That's not to say it was the same; it was definitely
different, but it's amazing how the same thing can be viewed through
different lenses and be valuable in different ways for different age
groups.
somewhat higher level because the kids here had been studying weight
and volume and how to measure them. Because I had told Lorie I would
be doing this activity, she sneaked in a lesson on density before my
visit. So I was able to discuss how density related to the
experiment. (What they remembered about density is that it's "weight
and volume together", but they were not able to articulate just how,
so this served as a good reinforcement.)
A few notes to myself on implementation: (1) the little rocks at
Lorie's house are great for shoveling in the bottles easily; (2) the
right kind of water container (low and flat) is really important,
because high walls and/or deep water is a big inconvenience; and (3)
don't let any kids fill their bottle with sand!
Overall, I'd say it worked just as well with the elementary as it did
with Primaria. That's not to say it was the same; it was definitely
different, but it's amazing how the same thing can be viewed through
different lenses and be valuable in different ways for different age
groups.
Sunday, October 16, 2011
A boat which sinks on purpose
This builds very well on the previous pre-K/K activity, in which we
investigated what floats and what sinks. By the end of that
activity, the kids had figured out that sinking a plastic soda bottle
takes quite a bit of effort. They need to put in some heavy things
like rocks (small ones which fit through the neck), but that is not
enough; they also had to get rid of most of the air by replacing it with
water. We started by reviewing what we had learned last time (by me
asking them questions, not by me lecturing).
After reviewing the basics, I showed them a bottle with some rocks in
it and the cap on and asked them if it would float or sink. Many of
them had forgotten how easily it floats unless it's really full of
rocks. We talked about boats, how they float because they have lots
of air inside (we had made aluminum-foil boats last time), and how a
submarine is special because it has to sink when desired but then has
to float again when desired. Most kids are under the misconception
that submarines dive just by having their engines push them down, but
if so then subs would have to have engines roaring just to stay still
underwater. Instead, they really do sink. We talked about how the
rocks inside represent heavy stuff that has to be on the submarine,
like engines and other equipment, people, etc, and also how there
still has to be some air on the submarine for people to walk around
and breathe.
So I challenged them to make a bottle almost sink with heavy stuff,
and then I would help them with the next step. I brought a box of
small rocks, and one bottle per child. They consistently
underestimate how many rocks it takes to sink the bottle with the cap
on. It needs to be about 2/3 full (although a fair fraction of this
2/3 is still air pockets between the rocks). When a child was ready
test, I put on the cap for them and tested it even when I knew it
wouldn't sink. Eventually they got close enough, but next time I
might consider marbles or something similar which would roll into the
mouth of the bottle more easily than irregularly shaped rocks, some of
which were too big anyway. The kids got a lot of practice making
predictions that it would sink, testing those predictions, and
modifying their hypotheses.
Before class, I had drilled two small holes in each bottle so water
could enter and exit if desired. These were drilled along one side,
which is considered the bottom of the sub when the bottle is floating
lengthwise, somewhat resembling the actual shape of a sub:
With enough ballast to get it close to sinking, I gave the kids new
caps which had had holes drilled and straws inserted through the holes
in a (nearly) watertight manner. It worked well that each kid got the
ballast done at different times, so that I could do some one-on-one
with each at the critical moment. I pointed out how the darn thing
still wouldn't sink, and why do they think it wants to float so much?
We would eventually hit on the idea of getting rid of the air using
the straw. Many of the kids were not old enough to know the difference
between blowing and sucking! They were supposed to suck the air out,
thus pulling water in through the holes on the bottom. Many blew to
begin with, but figured it out.
When they finally got it to sink, it was cause for high-fives. I made sure to
point out that there was still air in the sunken sub, so the crew would still be
able to breathe. I then challenged them to get it to float again, which involves
blowing on the straw, thus forcing water out through the bottom holes.
From that point on, it was just fun time as kids experimented with
their creations.
I think we took about 20 minutes per group of five students. I would
recommend using a shallow container of water such as a water table,
not an aquarium! Water deeper than say 6 inches is just unnecessary
and a pain....straws are only so long, and high aquarium walls make it
difficult to reach.
This activity was pretty successful in terms of student interest. The
first group was the most difficult, because they had to put in all the
ballast, which was a lot of work. After that, I took out just some of
the ballast between groups so that each group went through the process
without it being quite so arduous. As I wrote above, in the future I
should check out types of ballast which will go in more easily.
investigated what floats and what sinks. By the end of that
activity, the kids had figured out that sinking a plastic soda bottle
takes quite a bit of effort. They need to put in some heavy things
like rocks (small ones which fit through the neck), but that is not
enough; they also had to get rid of most of the air by replacing it with
water. We started by reviewing what we had learned last time (by me
asking them questions, not by me lecturing).
After reviewing the basics, I showed them a bottle with some rocks in
it and the cap on and asked them if it would float or sink. Many of
them had forgotten how easily it floats unless it's really full of
rocks. We talked about boats, how they float because they have lots
of air inside (we had made aluminum-foil boats last time), and how a
submarine is special because it has to sink when desired but then has
to float again when desired. Most kids are under the misconception
that submarines dive just by having their engines push them down, but
if so then subs would have to have engines roaring just to stay still
underwater. Instead, they really do sink. We talked about how the
rocks inside represent heavy stuff that has to be on the submarine,
like engines and other equipment, people, etc, and also how there
still has to be some air on the submarine for people to walk around
and breathe.
So I challenged them to make a bottle almost sink with heavy stuff,
and then I would help them with the next step. I brought a box of
small rocks, and one bottle per child. They consistently
underestimate how many rocks it takes to sink the bottle with the cap
on. It needs to be about 2/3 full (although a fair fraction of this
2/3 is still air pockets between the rocks). When a child was ready
test, I put on the cap for them and tested it even when I knew it
wouldn't sink. Eventually they got close enough, but next time I
might consider marbles or something similar which would roll into the
mouth of the bottle more easily than irregularly shaped rocks, some of
which were too big anyway. The kids got a lot of practice making
predictions that it would sink, testing those predictions, and
modifying their hypotheses.
Before class, I had drilled two small holes in each bottle so water
could enter and exit if desired. These were drilled along one side,
which is considered the bottom of the sub when the bottle is floating
lengthwise, somewhat resembling the actual shape of a sub:
With enough ballast to get it close to sinking, I gave the kids new
caps which had had holes drilled and straws inserted through the holes
in a (nearly) watertight manner. It worked well that each kid got the
ballast done at different times, so that I could do some one-on-one
with each at the critical moment. I pointed out how the darn thing
still wouldn't sink, and why do they think it wants to float so much?
We would eventually hit on the idea of getting rid of the air using
the straw. Many of the kids were not old enough to know the difference
between blowing and sucking! They were supposed to suck the air out,
thus pulling water in through the holes on the bottom. Many blew to
begin with, but figured it out.
When they finally got it to sink, it was cause for high-fives. I made sure to
point out that there was still air in the sunken sub, so the crew would still be
able to breathe. I then challenged them to get it to float again, which involves
blowing on the straw, thus forcing water out through the bottom holes.
From that point on, it was just fun time as kids experimented with
their creations.
I think we took about 20 minutes per group of five students. I would
recommend using a shallow container of water such as a water table,
not an aquarium! Water deeper than say 6 inches is just unnecessary
and a pain....straws are only so long, and high aquarium walls make it
difficult to reach.
This activity was pretty successful in terms of student interest. The
first group was the most difficult, because they had to put in all the
ballast, which was a lot of work. After that, I took out just some of
the ballast between groups so that each group went through the process
without it being quite so arduous. As I wrote above, in the future I
should check out types of ballast which will go in more easily.
Sunday, October 2, 2011
Floating and Sinking
Most kids love playing with water, and in hot weather water is a good thing to do science outdoors with. (Not to mention that the ocean is the theme in Primaria this year!) Discovering what sinks and what floats is a natural entry point for science because it is so simple that the youngest kids can appreciate it, yet it can lead to quite sophisticated concepts for the older ones who are ready to handle those. Furthermore, I designed this activity to lead naturally up to a submarine-building activity I want to do next time.
I started with just a simple glass of water visible. I asked each
child if they thought a wood chip would float or sink. For me, this
next step is really important. If the vote is not unanimous, I ask if
we can settle the issue just by counting the votes. Science is not a
democracy! We have to do the experiment and pay attention to the
results if we want to make any progress! And if the vote is unanimous, I
ask them if maybe we don't need to do the experiment. We agree
(sometimes with some nudging from me) that even if we all think it's
going to float, we should still do the experiment because sometimes we
could all be wrong in our predictions. I really want to emphasize
these aspects of the scientific method as early as possible, and this
activity is a good place to do it.
Then I repeat with several objects, such as a stone, a marble, a piece
of plastic, a bolt, a paper clip, etc. The kids have some idea that
lighter things are more likely to float, so the paper clip gives some
pause. I try not to use the word "density" because this means nothing
to the pre-K/K kids, but I do try to summarize that floating/sinking
is expected for something that is light/heavy for its size, not just
light/heavy in some absolute sense.
Then we get to the more interesting demo. (Some of them desperately
want to play with this stuff already, but I promise they can play if
they pay attention for just a bit longer.) I pull out a hard-boiled
egg and we see that it sinks. But if I add plenty of salt to the
water, the egg begins to float. This shows that the salt is mixing
with the water in a way which makes the water heavier. (By the way,
floating an egg is apparently how people used to determine they had
added enough salt to their pickling solution when making pickles.)
Then we repeat the whole thing with sand. Try as we might, the egg
does not float and the sand just collects at the bottom rather than
dissolving in the water. Here we have the observational basis for
some chemistry: salt in water forms a solution, but sand in water does
not. (I didn't state it this technically, but we did talk about how
ocean water behaves at the beach...the salt is an integral part of it,
as we can tell by its taste, but the sand is not.) We also have the
idea of different kinds of mixtures, which ties in nicely with the
previous pre-K/K science activity.
Finally we get to the play time. But this is serious play. I bring
out one tub of water in which I place some aluminum-foil boats.
Although they are metal, they do not sink. I challenge them to figure
out how to sink the boats. In parallel, a second tub contains empty
8-oz plastic soda bottles which I also challenge the children to sink.
The challenge aspect is really important. They come up with the ideas
and try them out. It seems like play time, but it has a purpose. This
particular challenge has the extra purpose that it builds up to the
future submarine activity.
With the foil, I have extra challenges ready for those who quickly
figure out how to sink the boats with stones. I challenge them to sink
the foil just by crumpling it up into a ball. It is surprisingly
difficult to do this; small air bubbles trapped in the foil are
surprisingly effective at floating it even after squeezing as hard as
possible. Some of them easily recognize that air bubbles must be the
problem, while others need some hints. The persistent ones finally
succeed in hammering out the air bubbles using anything vaguely
hammer-like. Meanwhile, others have gone in a slightly different
direction, crumpling the foil around a stone so that it forms a ball
with high average density.
With the plastic bottles, students take one of two initial strategies:
filling the bottles with water, or with stones/sand. Those who try
water see that water is not heavier than water, so that a waterlogged
plastic bottle still does not sink. Then they tend to start over with
stones/sand. However, the stone/sand strategy is surprisingly
ineffective. You can fill a bottle 1/4 full or even 1/2 or even 2/3 full of
stones/sand and it still doesn't sink. There's just too much air in
the bottle. However, few students have the patience (or the time left
in the activity) to fill the small-necked bottle completely with stones/sand.
They figure out (possibly with some hints) that they can
replace the bothersome air with water and finally get it to sink.
This is really good background for the submarine activity!
I think we spent 20 minutes with each group of about 5 kids, and that
was the perfect amount of time and the perfect size group. Larger groups could be
accommodated with more tubs of water; more than 3 kids per tub would not be good.
I started with just a simple glass of water visible. I asked each
child if they thought a wood chip would float or sink. For me, this
next step is really important. If the vote is not unanimous, I ask if
we can settle the issue just by counting the votes. Science is not a
democracy! We have to do the experiment and pay attention to the
results if we want to make any progress! And if the vote is unanimous, I
ask them if maybe we don't need to do the experiment. We agree
(sometimes with some nudging from me) that even if we all think it's
going to float, we should still do the experiment because sometimes we
could all be wrong in our predictions. I really want to emphasize
these aspects of the scientific method as early as possible, and this
activity is a good place to do it.
Then I repeat with several objects, such as a stone, a marble, a piece
of plastic, a bolt, a paper clip, etc. The kids have some idea that
lighter things are more likely to float, so the paper clip gives some
pause. I try not to use the word "density" because this means nothing
to the pre-K/K kids, but I do try to summarize that floating/sinking
is expected for something that is light/heavy for its size, not just
light/heavy in some absolute sense.
Then we get to the more interesting demo. (Some of them desperately
want to play with this stuff already, but I promise they can play if
they pay attention for just a bit longer.) I pull out a hard-boiled
egg and we see that it sinks. But if I add plenty of salt to the
water, the egg begins to float. This shows that the salt is mixing
with the water in a way which makes the water heavier. (By the way,
floating an egg is apparently how people used to determine they had
added enough salt to their pickling solution when making pickles.)
Then we repeat the whole thing with sand. Try as we might, the egg
does not float and the sand just collects at the bottom rather than
dissolving in the water. Here we have the observational basis for
some chemistry: salt in water forms a solution, but sand in water does
not. (I didn't state it this technically, but we did talk about how
ocean water behaves at the beach...the salt is an integral part of it,
as we can tell by its taste, but the sand is not.) We also have the
idea of different kinds of mixtures, which ties in nicely with the
previous pre-K/K science activity.
Finally we get to the play time. But this is serious play. I bring
out one tub of water in which I place some aluminum-foil boats.
Although they are metal, they do not sink. I challenge them to figure
out how to sink the boats. In parallel, a second tub contains empty
8-oz plastic soda bottles which I also challenge the children to sink.
The challenge aspect is really important. They come up with the ideas
and try them out. It seems like play time, but it has a purpose. This
particular challenge has the extra purpose that it builds up to the
future submarine activity.
With the foil, I have extra challenges ready for those who quickly
figure out how to sink the boats with stones. I challenge them to sink
the foil just by crumpling it up into a ball. It is surprisingly
difficult to do this; small air bubbles trapped in the foil are
surprisingly effective at floating it even after squeezing as hard as
possible. Some of them easily recognize that air bubbles must be the
problem, while others need some hints. The persistent ones finally
succeed in hammering out the air bubbles using anything vaguely
hammer-like. Meanwhile, others have gone in a slightly different
direction, crumpling the foil around a stone so that it forms a ball
with high average density.
With the plastic bottles, students take one of two initial strategies:
filling the bottles with water, or with stones/sand. Those who try
water see that water is not heavier than water, so that a waterlogged
plastic bottle still does not sink. Then they tend to start over with
stones/sand. However, the stone/sand strategy is surprisingly
ineffective. You can fill a bottle 1/4 full or even 1/2 or even 2/3 full of
stones/sand and it still doesn't sink. There's just too much air in
the bottle. However, few students have the patience (or the time left
in the activity) to fill the small-necked bottle completely with stones/sand.
They figure out (possibly with some hints) that they can
replace the bothersome air with water and finally get it to sink.
This is really good background for the submarine activity!
I think we spent 20 minutes with each group of about 5 kids, and that
was the perfect amount of time and the perfect size group. Larger groups could be
accommodated with more tubs of water; more than 3 kids per tub would not be good.
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