chemistry_chapter5notes

chemistry_chapter5notes - Chapter 5: Gases 5.1 Water from...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 5: Gases 5.1 Water from Wells: Atmospheric Pressure at Work How water is pumped from wells: Shallow well (less than 30 ft deep) – a pipe runs from a pump at the surface of the ground to the water below o creates a partial vacuum in the pipe o result is a pressure difference between the inside and the outside of the pipe pressure – a force exerted per unit area by gas molecules as they strike the surfaces around them Air contains gas molecules in constant motion that collide with each other and with the surfaces around them. Each collision exerts only a small force, but when these forces are summed over the many molecules in air they can add up to a substantial force. o greater external pressure pushes the water up the pipe to ground level and eventually to the tap where the water is used o Even if the pump could create a perfect vacuum (zero pressure) within the pipe, normal atmospheric pressure can only push the water to a total height of about 10.3 meters atmospheric pressure can vary by a few percent due to weather changes Deeper well (greater than 30 ft deep) – you must put the pump underground o the pump creates pressure exceeding atmospheric pressure o pushes the water up the pipe and to your faucet 5.2 Pressure: The Result of Molecular Collisions Variation in the pressure in Earth’s atmosphere creates wind, and changes in pressure help us to predict weather o pressure decreases with increasing altitude as air becomes thinner the fewer the gas particles, the lower the pressure o On Earth at sea level, the gas molecules in our atmosphere exert an average pressure of 101,325 newtons per squaremeter The pressure exerted by a gas sample, as defined previously, is the force per unit area that results from the collisions of gas particles with the surrounding surfaces: Page | 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Pressure Units Barometer – an evacuated glass tube whose tip is submerged in a pool of mercury o Because the density of mercury is 13.5 times that of water, however, atmospheric pressure can support a column of Hg only 1/13.5 times as high as a column of water. This shorter length—0.760 m, or 760 mm (about 30 in)—makes a column of mercury a convenient way to measure pressure o the mercury column rises with increasing atmospheric pressure and falls with decreasing atmospheric pressure The Manometer: A Way to Measure Pressure in the Laboratory Manometer – a U-shaped tube containing a dense liquid, usually mercury one end of the tube is open to atmospheric pressure and the other is attached to a flask containing the gas sample measures the pressure of the gas sample relative to atmospheric pressure o The difference in height between the two levels is equal to the pressure difference from atmospheric pressure If the pressure of the gas sample is exactly equal to atmospheric pressure, then the mercury levels on both sides of the tube are the same If the pressure of the sample is greater than atmospheric pressure, the
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/12/2010 for the course CHEM 111 taught by Professor Prutzman during the Spring '10 term at Lehigh Carbon CC.

Page1 / 15

chemistry_chapter5notes - Chapter 5: Gases 5.1 Water from...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online