**Project
3:
Experiments in Pressure
39-245: Rapid Prototyping
5/15/2000
Sara Lechleitner
Jennifer Stuber
Kyle Tsui
Goals
Our
main goal is to teach children about the relationship between the pressure
and temperature of a liquid.
Pressure
Bottle Barometer:
By experimenting, observing, and understanding the effects
of temperature and pressure on the behavior of their bottle barometers, the
children learn how barometers work and why they are useful for predicting changes
in the weather.
Other
Objectives:
· To demonstrate air pressure and its potential crushing ability.
- This is accomplished in the “Crushing with Air” experiment.
· To demonstrate the pressure, or pushing power, of air.
- This is accomplished in the “Paper Plunge” and “Seal with Air experiments”.
How Our Project Evolved
We began our project with the intent to teach children about the concept of pressure since Professor Finger did not have any other projects on the topic. Our first few prototype activities ended up getting canned or changed because they just did not work. Our main activity, the barometer, went through several revisions and adjustments. Towards the end of the project, we added in several more short, supplemental activities to help teach about pressure.
We tried a marshmallow activity where you draw a face on a big marshmallow, place it in a bottle, and then suck the air out of the bottle to decrease the pressure inside. The marshmallow is supposed to expand and a visible change in the face should occur. However, we could never suck out enough air for us to really see too much of a difference. We decided that to use this activity and have the children understand what was going on, we really needed a more observable activity.
The next activity we tried was a barometer. We originally tried using some play dough to seal the top, but it would work for a very short period until the air would seep through its pores. Instead, we ended up using clay for our seal since it doesn’t really leak. We also tried a variety of straws to see which one worked the best. We found that the stronger the walls of the straws were, the better the experiment worked. The regular bendy straws were too flexible. We ended up using a straw from one of our sports bottles for the best results.
After experimenting with the different straws, we tried to find a better way to suck the water up into the straw. The task sounds easier than we found it to be since you had to be able to suck up enough water so you could cover the straw opening with your finger and still have a decent level of water remaining in the straw. We also did not really want the children sucking up the water with the food coloring in it even though it would not harm them. Thus, we tried using a turkey baster to suck up the water, but it was even more difficult to hold. The best solution we found was to allow the students to suck the water up, but have them chewing gum when they do it and to use the gum as a plug instead of their finger.
The last issue we dealt with was whether to use the bottle cap. We discovered that if we didn’t use the bottle cap, the clay was not enough to form an airtight seal. Thus, we ended up using the cap, but just creating a hole big enough for the straw to fit through.
This activity did not work too well. It was way too difficult to find bottles with a small enough top. Plastic soda bottles worked better than glass ones because their openings were smaller. If we could have used a dollar or half dollar coin, we might have had a better change of getting this activity to work well, but this was not realistic. Thus, we ended up throwing out this activity.
This activity worked really well from the start. We found that the hotter the water is inside the bottle, the more the air will get excited and escape. Also, the cooler the ice water is (which means a greater temperature difference), the faster the bottle crushed. Another factor that could potentially affect the reaction time and whether the activity worked was the length of time you leave the bottle uncapped. If you place the cap back on too soon, it does not allow the air inside to get excited and escape. Lastly, this experiment worked best with thinner plastic bottles like bottled water.
This activity also worked really well. The only problems we had where that if you crumpled the paper up too tightly, it would not stay inside the bottom of the cup when you turned it upside down. It probably would have been better if we had used clear cups so that the students could see that the water level outside was in fact above that of the paper inside.
This activity was also very successful. You can pretty much do this activity with any type of cup or plate. To make things easy on ourselves, we used paper plates and Styrofoam cups. The only thing is that you want to make sure you do this experiment over a bowl or bucket so that when someone forgets to hold the plate when they flip over the cup, the water goes into the bucket and not all over.
By the time we presented at the Meeting of the Minds, our project had evolved to include the barometer as more of a take home activity and the three supplement activities as our main demonstrating tools. If you would like the barometer to help children understand pressure related to water, it is better to use water at room temperature and to instruct them to watch the barometer over a few days and see how the height relates to the pressure and weather. At the Meeting of the Minds, we could demonstrate how hot water inside the bottle and cold water outside could speed up this process. But doing so does not establish much of a link between pressure and weather.
What
Kids Learn and How They Learn It
Pressure Bottle Barometer
This project teaches students that at higher temperatures, there is higher
pressure and similarly, at low temperatures, there is lower pressure. With
this knowledge, students can predict the weather using their homemade barometers.
Students are taught these concepts by making and observing their barometers. The water level inside their barometers rises and falls because of air pressure exerted on the water in the glass. As the air presses down (increased atmospheric pressure) on the water in the glass, more water is pushed up into the tube, causing the water in the tube to rise. Similarly, when the air pressure decreases on the water in the glass, some of the water will move down out of the tube, causing the water level in the tube to fall. The change of barometric pressure will help students to forecast the weather. Decreasing air pressure often indicates the approach of a low-pressure area, which often brings clouds and precipitation. Increasing air pressure often means a high-pressure area is approaching, bringing with it clearing or fair weather.
In this project, students are taught about air pressure and its potential crushing ability.
In order to teach these concepts, students put some hot water into a plastic bottle, put a lid on it, let it sit, and then pour cold water over the bottle. The bottle retains its shape in a normal atmospheric condition because the air pressure inside the bottle is the same as the air pressure outside. The bottle collapses as the warm air inside the bottle cools since it exerts less pressure. The pressure of the air outside is stronger and crushes the bottle.
In this experiment, children are taught about how air actually has mass and takes up space does have pressure.
This experiment involved students plunging a cup with a paper towel at the bottom upside down into a tub of water. The paper towel does not get wet. This is because water can only get into the glass by displacing the air inside it. Air likes to rise, since it is less dense (lighter, essentially) than water. Since the top of the cup blocks the only way up, the air is trapped, and therefore will not let water move into the cup and touch the paper. Once all of the air is trapped at the top of the cup, it exerts a pressure down on the water, which is equal to the pressure that the water is placing upwards on the air.
This project demonstrates the pushing power, or pressure of air.
In order to learn more about this concept, students were given a cup and a plate. They put some water in the cup and then placed the plate on top of the cup. Once this was done, they turned the cup and plate upside down and the plate stayed attached to the cup. The water stays inside the glass because water and air inside the cup cause a suction force, which holds the plate against the cup. The sudden shifting of the water and air inside the cup acts in a similar fashion as a plunger.
Teacher
Instructions
Pressure
Bottle Barometer
(Teacher or Parent Instructions)
This project teaches students the fundamental concepts of pressure and how they relate to the temperature of a liquid. Upon the completion of this project, students should understand enough about pressure so that they are able to predict the weather through the use of a barometer.
Basic
Principles of a Barometer
Atmospheric pressure, the air pressure in the surrounding area, can be determined through the use of a barometer in which the height of a column of mercury or water is measured. The measured height can be converted into pressure using the following equation:
**
where:
PO = The pressure at the reference point (This is the point on the bottle where the
tape is applied)
P = The pressure that you are trying to determine
= The density of the fluid
(mercury = 13550 kg/m3, water = 999 kg/m3)
g = The force due to gravity (9.8 m/s2 or 32.2 ft/s2)
h = The change in height of the liquid inside the barometer
** It is not necessary for the students to understand this equation.
Results
of Homemade Barometers
At higher temperatures, there is a higher pressure within the bottle and therefore when the water in the bottle cools or if the bottle is submerged in cold water, the pressure inside the bottle will decrease and the water level in the straw will go down.
The students will notice that over time, the water level rises and falls. Tell the children to make sure to pay attention to the change in weather and its relation to how the water level inside the straw changes.
The water in the tube rises and falls because of air pressure exerted
on the water in the glass. As the air presses down (increased atmospheric pressure)
on the water in the glass, more water is pushed up into the tube, causing the
water in the tube to rise. Similarly, when the air pressure decreases on the
water in the glass, some of the water will move down out of the tube, causing
the water level in the tube to fall. The change of barometric pressure will
help students to forecast the weather. Decreasing air pressure often indicates
the approach of a low pressure area, which often brings clouds and precipitation.
Increasing air pressure often means a high pressure area is approaching, bringing
with it clearing or fair weather.
Children's
Instructions are Attached
Paper
Plunge
(Teacher or Parent Instructions)
This
project teaches students the princples behind air pressure. Upon completion
of this experiment, students will learn more about the principles behind air
pressure and mass.
Basic
Principles of the Paper Plunge
In order for this experiment to work properly, the glass must be plunged
straight down into the water. This will prevent any air from escaping. The
air is what prevents the water from entering the cup and coming in contact with
the paper. In order for the water to enter the cup, the air must first be displaced.
Air tends to rise, so it moves to the top of the cup to try and escape, only
to find a solid cup. With the air trapped, the water tries to push into the
cup, but will merely compress the air molecules more. This will increase the
air pressure, which will in turn push against the water and prevent it from
entering the cup. The deeper the cup is placed in the water, the harder the
water will push against the air to try and get into the cup. However, no matter
what the water tries, it will not be able to enter the cup and touch the paper.
If the cup is not plunged perfectly straight down, air will be able to
escape from the cup, which will allow the water to flow up into the cup. This
will possibly cause the water to touch the paper if the student is not careful.
Crushing
with Air
(Teacher or Parent Instructions)
This
project will teach students the princples behind air pressure and its curshing
abilitiy.
Basic
Principles of a Barometer
Once
hot water is poured into the soda bottle, this increases the air pressure and
energy of the air inside the bottle. This causes the air to flow out of the
bottle, into the atmosphere. Once the student seals the bottle however, this
will cause the bottle to have a lower air pressure than the atmosphere. However,
the air molecules inside the bottle are full of energy from the heat, and therefore
will push against the bottle walls, keeping the bottle in its proper shape.
When
the bottle is placed is cold water, the temperature of the air will drop rapidly.
This causes the air molecules to lose their energy and begin to slow down.
This causes the air pressure inside the bottle to drop. Since the bottle is
sealed, there will be no more air to try and equalize the air pressure in the
bottle. Thus, the air pressure outside the bottle will be sufficient to overcome
the pressure inside the bottle and crush it.
Seal
with Air
(Teacher or Parent Instructions)
This
experiment will teach students about the power of suction and air pressure.
Basic
Principles of a Barometer
When
the water is poured into the cup, air is displaced from the cup. When the plate
is placed on top of the cup, a seal of sorts is formed. Once the cup is flipped,
the water willhelp complete this seal and prevent any air from entering the
cup. This causes a suction effect. If there is any hole in the cup or if the
plate doesn’t fit relatively tightly onto the cup, this will fail and the water
will spill all over the place.
For
the suction effect to be created, the water cannot exit the cup. The plate
and to a degree the water itself forms a seal and prevents air from entering
the cup. The air in the cup will rise to the top, and try to push out without
success. Since no new air can enter the cup, only gravity will be acting on
the water to try and pull it out of the cup. However, for the water to exit,
something must take its place in the cup. If the water was somehow able to
exit the cup, a vacuum would be formed. Nature typically dosen’t like vacuums,
so the water is held in, thus holding the plate as well.
Modification
of Project for Different Age Groups
This project is geared towards children in middle school. At this age, they are able to understand the basic concepts of pressure, yet it is not too simple for them. Therefore, this project would be very hard to alter to encompass a wider age range. High school students would find the project somewhat simple and boring while children in elementary school would not be capable of understanding pressure.
Pressure
Bottle Barometer
Step 1:
Obtain
the following materials from your teacher or parent:
§
A juice bottle
§
A
clear plastic straw
§
A
fist full of clay
§
A
cup of warm water
§
A
bottle of food coloring
§
A
roll of masking tape
§
A
permanent marker
§
A
piece of gum
Step 2:
Start
to chew a piece of gum as you begin to prepare your barometer.
Step 3:
Pour the warm water into your juice bottle, filling it up about
halfway. (See Figure 1 – Fill Line.)
Step 4:
Add
five (5) drops of food coloring to the water.
Step 5:
Mix
the water and food coloring with the straw.
Step 6:
Suck on the straw until the water level 2 in the straw is above
the water level 1 in the juice bottle.
Step 7:
Place the gum that you have been chewing at the end of the straw
so that when you let go of the straw, the water level stays above the water
level 1 in the juice bottle.
Step 8:
Place
some clay around the mouth of the bottle and around the straw in order to form
an airtight seal.
Step 9:
Tear off a small piece of tape and place it on the outside of
the bottle so that the bottom of the tape is at the same level as the water
inside the straw. (See Figure 1 - Labeled Tape.)
Step 10:
Write the time and date on the piece of tape with the permanent
marker.
Crushing
With Air
Objective: To demonstrate air pressure and its potential crushing ability.
Materials Needed:
Instructions:
Step 1: Stand the bottle upright in a bowl.
Step 2: Pour the hot water into the bottle and leave it for a short time.
Step 3: Screw the top onto the bottle.
Step 4: Lay the bottle in the bowl and pour ice-cold water over it.
Step 5: Stand the bottle up.
Questions:
· What happened?
· Which is stronger – the pressure of the air outside or the pressure of the air inside the bottle?
· What made the bottle crush?
* The bottle retains its shape in a normal atmospheric condition because the air pressure inside the bottle is the same as the air pressure outside. The bottle collapses as the warm air inside the bottle cools since it exerts less pressure. The pressure of the air outside is stronger and crushes the bottle.
Paper
Plunge
Objective: To demonstrate the pressure, or pushing power, of air.
Materials Needed:
Instructions:
Step 6: Fill the bowl with water.
Step 7: Crumple up a piece of paper and place it into the bottom of the glass.
Step 8: Plunge the glass straight down into the bowl of water.
Questions:
· What happens to the paper?
· Where is the water level in the glass?
* Water can only get into the glass by displacing the air inside it. Air likes to rise, since it is less dense (lighter, essentially) than water. Since the cup blocks the only way up, the air is trapped, and therefore will not let water move into the cup and touch the water.
Seal
with Air
Objective: To demonstrate the pressure, or pushing power, of air.
Materials Needed:
Instructions:
Step 9: Hold the glass over a bowl.
Step 10: Pour some water into the glass.
Step 11: Place the plate or card on the glass.
Step 12: Hold down the card (or plate) so that it touches the rim all the way around. (If there are any gaps, this experiment won’t work!)
Step 13: Still holding the card, turn the glass upside down.
Step 14: Let go of the card (or plate).
Questions:
· What happened?
· What made the water stay inside the glass?
* The water stays inside the glass because water and air inside the cup cause a suction force, holding the plate against the cup. The sudden shifting of the water and air inside the cup acts in a similar fashion as a plunger.