Sucking Students into an Understanding of Air
Pressure and Vacuums
Lesson Plans & Teaching Notes
OBJECTIVES
- Students will experience science as a way of understanding
and explaining based on evidence and argument.
- Students will develop and test their ideas about air
pressure and vacuums by doing investigations into movement
of fluids in tubes.
- Students will relate their experiences and ideas to the
historicalinvestigations concerning the existence of vacuums
and the role of air pressue in the movement of liquids
in tubes.
Rationale
In the history of science, the some of the most intense and
fruitful investigations have been about understanding common
events. For example, understanding the "rising" and "setting" of
the sun and moon or the paths of falling objects caused a great
deal of scientific inquiry. To fully explain many of these
common events, you must be able to conceptualize something
that may contradict your direct experience or is beyond your
perceptual abilities.
To accept the heliocentric world view necessitates that
you must accept an idea that is not apparent from direct
experience. We all see the sun "rise" and "set".
The simplest explanation is that the world is stationary
and the stars and planets revolve around the Earth. This
explanation is also wrong. The better explanation is hidden
in the fact that we can not directly sense the speed and
relative motion of the Earth as it rotates and revolves around
the sun.
The problem associated with understanding the effect of
air pressure is the relative difficulty in perceiving that
air has weight or that is actually exists. Air is colorless,
tasteless, and extremely light. It's presence is so common
that we take it for granted unless you are submerged in water
or in a tornado. The awareness of air itself, not to mention
the pressure it exerts, is not readily apparent in our daily
experience. Think about how many times you have described
a glass NOT FILLED with water or some other fluid as being
EMPTY! If you don't perceive the existence of a substance
it is impossible to use it to explain phenomenon that you
experience.
Click for more historical
background.
Click for details on ACTIVITIES.
Day 1
Introudce Behavior of Fluids Ideas and Historical Apporach.
Science as a process to explain and understand things based
on observation and evidence has been the standard definition
in my science class. I inform students of my belief that when
students are asked to learn science concepts in class they
are retracing similar steps that great science minds have taken
to understand phenomenon. Basically, we ask them to learn something
that could have taken hundreds or thousands of years to understand
in a matter of days. In science class, we compress and simplify
the time and energy that was spent investigating how something
works and present it to students as if it had no life of its
own and disregard the human effort it takes to really understand
something. Is it any wonder that science is seen as difficult,
complex, confusing and just plain hard? The focus of this unit
will be in phenomenom related to the behavior of fluids, meaning
substances like water and also air that have the ability to
flow.
Activity 1
Become aware of student concepts and knowledge.
Get baseline information on student concept of how water goes
up a tube that you suck on. Demonstrate using blue
food coloring in water and a long clear plastic tube. Ask students
to explain as completely as possible to describe how water
moves up the tube and down the tube or why it doesn't go up
unless you do something to the tube. Ask them to provide a
diagram to help show their ideas. Work in pairs and turn in
a single piece of paper that best explains the phenomenon.
The teacher should not use the words suck, suction, vacuum,
pressure, etc. Your job is to perform the demo and make sure
that students give complete descriptions. Collect data and
review. Try to break down the basic concepts and ideas to help
you understand them. Keep these ideas for later, when you try
to put together the effect of air pressure on the behavior
of liquids in tubes.
POINT TO MAKE.....Your ability to explain depends on the
information, awareness and tools that you have to think with.
Which explanation is CORRECT? Most all students will ask
this question. ANSWER....There is no correct explanation.....Only
better or more functional or more complete or detailed or
logical or consistant. It depends on the tool box of ideas
that each one brings to the task. Science is the attempt
to explain the world around us and make it more understandable.
The level at which you understand, question, and perceive
depend on one another. The more you know, the better your
questions and the more you notice.
Activity 2
Exploring the materials and event.
Explore and Record Observations, Infer, and Develop Theories
about how different plastic bottles drain water and the factors
that control the rate of draining.
Students are to work in pairs to explore, inquire, mess
around, get to know the ways in which different plastic bottles
drain water. All bottles have the same size whole in the
bottom at approximately the same distance up from the bottom.
The bigger the variety of sizes and shapes the better.
TASK: Record as many observations, measurements and inferences
as you can about how water drains out the bottom. Make a
list of factors that you think control the rate of flow of
water out of the containers. Be prepared to report your findings
in a class discussion.
Note.....If your room is not equipped with a mop and bucket
get one. This activity will provide some good reason to clean
that dirty floor of yours.
Day 2
Activity 1
Class discussion and record of observations, inferences,
and factors controlling the rate of water flow.
Use a large piece of paper to record student observation and
ideas. This should be a time where any and all comments are
recorded. Focus should be on info collected on rate of flow
and length of stream. Under what conditions did the rate change
or length of stream change? Is the rate of flow constant? Measurements
of flow rate. The observations should be descriptions of what
happened. The facts of the event.
On the same piece of paper, Refer to the observations and
let students put together the inferences about the relationship
between volume and flow rate, flow rate and length of stream,
pressure and flow rate, pressure and length of stream, volume
and pressure, weight of water and pressure, etc. The inferences
should be logical conclusions based on the observations made.
Make a list of all the possible factors that did or could
effect the flow rate or length of stream of water (all of
which would indicate a change in pressure).
Activity 2
Find a Focus Question and Design an Experiment.
Students are to pick one of the factors discussed and record
a focus question and design an experiment to find evidence
for the predictions and hypothesis they make. (What will happen
if the factor is changed? Explain why.)
Example:
- Focus Question.
- How does the volume of the water effect the rate of flow?
- Prediction
- Increasing the volume will increase the rate of flow.
- Hypothesis
- Water has weight and exerts pressure. The more water
in the container means more pressure. The higher the pressure
the faster the rate.
- Procedure
- Using the same container put different volumes of water
in it and record the amount of water that drains outs in
30 seconds. To maintain a constant rate of flow water will
be added to keep water at a constant volume. Record 3 trial
at 4 different volumes and calculate rate.
- Data
- Make a table of time, volume, volume added, height, type
of container.
- Conclusion
- Reflect on your prediction and hypothesis. Did your results
match what you said would happen? What explanation or new
experiment might you try next to help solve the problem
of what factors control the rate of flow?
Day 3
Activity 1
Collect data and analyze results.
The lab should have all the needed equipment.....water, plastic
containers, nail and a heat source to make new holes, clock,
beakers or graduates to measure volumes, and the most important
device.....MOP AND BUCKET, also SPONGES.....
Students should be working in pairs or threes and should
have an experimental design to follow. Check them off and
let those most prepared start first. Move around the room
and check their quality control and question them about what
is happening and get them to try to explain the results they
are getting. When the data is collected each group should
discuss their findings and be prepared to report.
Activity 2
Present preliminary findings and find any points of controversy
or descrepancy
Using sheets of paper large enough to see from a distance (20inx20in.),
have each group record their focus question, prediction, hypothesis,
data, and conclusion. Post the report in a visible area. Ask
groups to read through 3-5 and record any questions they might
have about how the data was collected or the logic or conclusion
that was made. Look for any pattern or relationship that seems
obvious and write a statement about the effect the factors
that were tested had on the flow rate.
Redefine the problem in terms of pressure and force and
discuss.
Final Note
As a true believer in the fact that Science
NEVER Sucks, I would appreciate any input from
you concerning the topic of suction, air pressure, and
vacuums. Comments on your experiments and special activities
or demonstrations that you may have about this mysterious
topic would be welcome. I hope that you try some of these
investigations in your own classroom. Just remember to
let your students do the work of explaining and theorizing.
The things they come up with will surprise you and your
students will enjoy taking ownership of their learning
while confronting the perceptions they have of the mysterious
world around them.
Please send any information to: chuckb@cjhs.centennial.k12.mn.us
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