Additional Material Features
Below is an excerpt from Unit H of Additional Material
|Unit H - Behavior of Gases
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Insights: Chemistry and the Body—Diving and Henry’s Law
Have you ever noticed gas bubbles forming inside a glass of soda pop? These bubbles only appear because the liquid is no longer under enough pressure to hold the gas in solution. The decreased pressure reduces the amount of gas that can be dissolved. This dependence of gas solubility on pressure is called Henry’s Law.
Both pilots and divers can experience a condition known as the “bends.” The name for this condition probably resulted from the fact that the diver is doubled over with pain. This condition is really a sickness caused by rapid decompression.
The bends results from the formation of bubbles of nitrogen gas in the blood and body fluids. Under high-pressure conditions, significant amounts of nitrogen from the air we breathe are dissolved in body fluids. A sudden reduction in atmospheric pressure causes the solubility of nitrogen gas to decrease. The excess nitrogen gas forms bubbles. Wherever the nitrogen bubbles form, normal circulation to that part of the body is cut off.
If a bubble cuts off circulation in the brain, dizziness, blindness, paralysis, convulsions and unconsciousness may result. In the joints, great pain is experienced. In the lungs, choking and asphyxia result. If a bubble forms in an artery supplying blood to a vital organ, such as the heart, the victim can die of a “heart attack.”
If a diver returns too rapidly to the surface of the ocean from a deep dive, he or she may get the bends and it may, in some cases, be fatal. A similar condition can result from a pilot climbing to high altitudes too rapidly. Having the diver breathe a special mixture of gases can reduce the danger of getting the bends. One such mixture is helium and oxygen. Helium is less soluble in the blood and in any body fluids than nitrogen. Therefore, bubbles of helium are less likely to form as the diver is brought to the surface. Another way to prevent the bends is to decompress slowly. The diver stays a period of time at each higher level. His lungs remove the nitrogen dissolved in his body fluids during normal respiration without forming bubbles.
Another related condition is called nitrogen narcosis or “rapture of the deep.” The body experiences a drug-like stupor at higher concentrations of nitrogen. Diving only for short periods of time or using a helium-oxygen breathing mixture can eliminate this problem.
Ascending from the Depths:
One way to remove air from body cavities is for it to pass into the veins. If bubbles form from decreased pressure, they circulate through the blood until they plug small arteries and capillaries. An embolism is the name given to such a result and it can lead to unconsciousness and death. Air can also pass into the space between the lungs and the heart known as mediastinum. This produces a type of emphysema that causes severe chest pain, breathing problems and faintness. If air gets between the lungs and the rib cage, the lungs collapse. This is called pneumothorax.
Divers must learn never to hold their breath. Scuba divers are taught to breathe normally and to exhale during ascents.
A Closer Look: How Heavy Is Your Car?
To estimate the weight of your car.
Predict the weight of your car.
Ensure the car is parked with the emergency brake engaged.
Data and Results:
Record your data and results in the appropriate table. Calculate the percent error.
Explain what you learned by doing this experiment. What are some possible sources of error in this experiment?
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