egg pressure (Alan Kodel)
Principle(s) Investigated: List all principles that apply to this activity.
PH3. Energy cannot be created or destroyed, although in many processes energy is transferred to the environment as heat. As a basis for understanding this concept:
PH3.a. Students know heat flow and work are two forms of energy transfer between systems.
PH3.b. Students know that the work done by a heat engine that is working in a cycle is the difference between the heat flow into the engine at high temperature and the heat flow out at a lower temperature (first law of thermodynamics) and that this is an example of the law of conservation of energy.
PH3.c. Students know the internal energy of an object includes the energy of random motion of the object’s atoms and molecules, often referred to as thermal energy. The greater the temperature of the object, the greater the energy of motion of the atoms and molecules that make up the object.
PH3.d.Students know that most processes tend to decrease the order of a system over time and that energy levels are eventually distributed uniformly.
Materials:
glass bottle
newspaper
hard boiled egg
matches
Procedure:
1. light a piece of newspaper on fire.
2. put the burning newspaper inside the empty glass bottle.
3. place the hard boiled egg over the lid of the glass bottle with the skinny end facing down.
Data Table
https://docs.google.com/spreadsheet/ccc?key=0AmKL_QQ18dCNdGZNbV96cGhhdjlaUDNZM0xPV2VTZ0E#gid=0
Student prior knowledge: Students should know that heating particles cause them to move more rapidly. People should also know that particles move from areas of high pressure to low pressure.
Explanation: In this experiment, a burning piece of newspaper is placed in an empty bottle. This caused the air particles to to start moving more rapidly which increases pressure. The heated air inside the bottle begins to escape into the environment which leaves fewer air particles in the bottle.. The Hard boiled egg is put over the bottle and eventually the flame goes out. Once this happens the air inside the bottle cools to the same temperature as the outside air and it condenses. This causes the pressure inside the bottle to be lower than outside the bottle. The denser external air pushes the into the bottle in order to to get to the lower pressure environment.
Questions & Answers:
1. How could you get the egg back out of the bottle intact?
Answer: Hold the bottle upside down with the egg blocking the mouth of the bottle. Then pour boiling water over the bottle until the air inside the bottle pushes the egg through the mouth of the bottle.
2. If a person is choking, how can pressure be used to save that person's life?
Answer: The Heimlich Maneuver. During abdominal compressions it creates increased pressure in the lungs which pushes the object out of the throat in order to balance the pressure between the internal and external environment.
3. Why shouldn't a scuba diver hold their breath while ascending?
Answer: If a diver holds their breath while descending the increase in water pressure will compress the air in the lungs which in itself poses no danger to the diver. However if a diver holds their breath while ascending to the surface, the volume of air in the lungs will increase due to the decrease in outside pressure. If the volume of air increases more that the lungs can handle, the diver may experience lung expansion injuries.
Applications to Everyday Life:
1. Scuba diving is a perfect example of how pressure can be used in everyday life. A scuba tank contains compressed air which is used by the diver to breathe under water. The diver has a regulator in their mouth at all times which acts as a valve to prevent leaking in the air tank. When the diver takes a breath, the valve opens and the high pressure air in the scuba tank moves into the empty low pressure lungs of the diver which allows them to breathe under water.
2. The idea that heat caused atoms to spread farther apart was very important in the invention of the mercury thermometer. By heating a glass tube with mercury in it, one could track the temperature by looking at how much the mercury expanded or condensed in the glass tube.
3. Breathing is another example of how pressure is needed in every day life. During inspiration the diaphragm contracts it creates low pressure in the chest cavity. The higher pressure surrounding air is then forced into the lungs. During expiration the diaphragm relaxes which creates high pressure in the chest cavity which forces air out of the lungs to equalize the internal and external pressure.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.