chapter5gaslaws

chapter5gaslaws - Air is there How d we know that air is...

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1 Gas Laws Chapter 5 Air is there ± How d we know that air is real? ² A mouse in a closed container doesn’t live ² Four tires full of air support a big Explorer (until a nail gets in the tire) ² We blow up a balloon. Take that balloon into a swimming pool (under water) ² Take that balloon into a swimming pool (under water). Does it get bigger or smaller? ± Notice American Vacuum Society “image committee” logo “No Hoovers”. A vacuum cleaner uses a simple vacuum pump to pull dirt out (as it pulls air) off the carpet. ± If we take the air out of this sphere, can you pull the halves apart? Air makes things happen ± We can make a model car fueled with baking soda and vinegar. ± We can pull water from a well or use a straw to suck up liquid. We can push air into a deeper well to get ± We can push air into a deeper well to get water out ± We can lift heavy objects with balloons ± We can clean the carpet. ± We can make explosions to do work How do you study something you can’t hold? ± Ever hear “the barometric pressure is low, it’s going to rain” or “the pressure is high, the weather looks good”. Weather people have a tool to measure atmospheric pressure. ± If you had a really long straw, how high could you pull water up? ± We can compare liquid vs. . air. Air can hold up liquid. Do you know who used to study this and when? 1630-1640s ± What was Galileo known for? ± He had a minor problem, he was under house arrest-couldn’t travel. But he still could do experiments experiments. ± He wanted to study how to get water out of a mine (kind of hard to mine ore under water). ± Their vacuum pumps couldn’t pull > 39 feet. Why? ± He is credited with the creating the water barometer, to study air pressure. What’s a Barameter? ± Start with a long tube or hose, capped at one end. ± Fill it full of water or other liquids, cap the open end ± Turn it upside down and suspend the capped end from a tall pole or…whatever ± Open the other end UNDER Liquid ± The height of the water is a function of the air pushing down (the atmosphere) ± How high is this? For water, at sea level, about 34 feet.
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2 Galileo had a student, who could travel: Torricelli: ± He did two major things: rather than use water, he used liquid mercury, 13.5 x more dense. His barometer was less than 1 meter high (.76 meter). This barometer was portable and he could travel to the top of a portable and he could travel to the top of a mountain, where he found that the pressure (height of mercury) was lower. ² At higher altitude, the air pressure is lower. (you can’t work so hard when you’re at Tioga Pass and why airplanes are “pressurized”- there much less oxygen in the air above 12,000 ft. Magdeburg Sphere: Pull the air out of the sphere and 8 donkeys can’t pull the sphere apart. (anout 1672) How do we know that atm pressure is 14.7 pounds per square inch? Here’s a way; Take the air out of the sphere and see how much weight is required to pull the halves apart.
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chapter5gaslaws - Air is there How d we know that air is...

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