Learning Objectives

  1. Understand what is atmospheric pressure

  2. Understand the effects of low and high atmospheric pressure on the human body especially under extreme conditions

Definition of atmospheric pressure

  • Pressure generated as a result of air molecules above the matter bombarding randomly onto the matter

  • Generated by the amount of air particles in the atmosphere above the object

  • Which at sea level has a mean value of 101,325 pascals (roughly 14.6959 pounds per square inch)

  • Refer to Atmospheric Pressure for more details

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Effects of low atmospheric pressure

1.Altitude training

At high altitudes (1500m and above), there is still approximately 21% of oxygen in the air, but due to the low atmospheric pressure (B < A), the partial pressure of oxygen is reduced. Due to the pressure gradient, significantly more energy is also required for the lungs to take in oxygen. Hence, to adapt to the difficulty of obtaining and lack of oxygen, the body will increase the mass of red blood cells and hemoglobin in the blood, as well as reduce muscle metabolism to enable a more efficient use of oxygen. This effect is able to last for up to 2 weeks after returning to lower altitudes giving altitude trained athletes a competitive advantage.

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2.Illnesses
osteoarthritis
osteoarthritis

When the atmospheric pressure drops, tissues expand. The expansion of tissues in and surrounding joints aggravates the nerves, causing pain. Thus, patients living in geographical locations with a higher atmospheric pressure tend to experience a greater severity of osteoarthritis (pain in the joints due to expansion of tissues).

Drops in atmospheric pressure also have an impact on headaches, particularly sinus headaches. When atmospheric pressure drops (such as in an ascending airplane or before a storm), gases in the sinuses and ears are at a higher pressure than those of the surrounding air. The air pressure tries to equalize, causing pain in the face and ears. Those that suffer from chronic sinusitis or have a cold have the most issues, as the air becomes trapped in the sinuses and is unable to equalize.

Demonstration 1

  • Effect of a vaccuum (lack of atmospheric pressure) on the human body

  • Effect of increased atmospheric pressure on lung activity

Apparatus

  • 1x Huge test tube

  • 2x Thin, unelastic plastic bag

  • 1x Blu tack

Procedure

Observations/ Demo video


Explanation

Conclusion

Initial atmospheric pressure

Change in atmospheric pressure

Final atmospheric pressure

Change in volume of balloon

Best experimental result
















Effects of high atmospheric pressure

Illnesses

Increases in atmospheric pressure (such as in a descending airplane) results in a condition called “ear popping” where air particles rushes into the ears to balance out the pressure inside and outside of the ears. This may result in pain for some people.

Other health effects of high pressures such as that during diving could be found at Effects of Hydrostatic Pressure on the human body.

Demonstration 2

  • Effect of increased atmospheric pressure on the human body (represented by a can)

Video

This train tank was left in the sun with its vents open. Later in the evening, the vents were closed and the tank was left through the night (when is gets cold).

*Disclaimer: not done by us, try at your own risk!*

However, there is also a mini version for you to try out, but also at your own risk. Read on to find out more :)

Apparent

  • 1x Soft aluminum cans (representing the lungs/ human body)

  • 1x Bunsen burner

  • 1x Wire gauze

  • 1x Tripod stand

  • 1x Tongs

  • 1x Plastic basin


Procedure

  1. Fill the plastic basin with ice water and place the basin near the Bunsen burner


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  2. Fill one third of the aluminium can with water


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  3. Heat the aluminium can till the water boils


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  4. Allow the water in the can to boil for approximately 60 seconds more


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  5. Using the tongs, quickly turn the can upside down and place it in the basin of ice water


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Observations

(video)

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The can implodes!

Explanation

Before the can is heated, the gas inside it is completely filled with atmospheric air and there is no difference between the air pressure on the inside and the outside of the can.

When the water in the can begins to boil into gaseous steam, it takes up a greater volume than before, forcing out atmospheric air which had previously occupied the can.

As the can is placed into the basin of ice water, the can and thus the steam are cooled rapidly. The steam condenses quickly back into liquid water and thus occupies a much smaller volume. As the hole in the can is submerged in ice water, atmospheric air is not able to rush in and fill that volume. Hence, the air pressure in the can decreases and is now much lesser than the surrounding air pressure. The can is crushed from it weakest points (the sides), by the net inward forces exerted by this pressure difference.

Although some ice water is drawn up into the can due to the pressure difference too, the can hole is too small to draw in the ice water quickly enough before the can is crushed. Therefore, for the experiment to work, ice water is used to ensure that the volume decrease due to condensation of steam is greater than the volume increase due to the intake of water per unit time.

Conclusion



















References



Done By

Neo Yu Yao Terence | Chua Jie Han | Sha Yicheng