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How it works

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by

Valerie Henderson

on 1 April 2016

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Transcript of How it works

How it works!
How does a vacuum cleaner work?
Hot Air Balloons
Hot air balloons work because of the density difference between hot and cold air.
What is density?
Density is a measure of the ratio of mass per unit of volume.
Straws
How does a straw work?
How it works
-gas laws applied to the world around you

Inside vs Outside Pressure
Straws
Vacuum Cleaners
Atmospheric Pressure
Ears popping
Dalton's Law of Partial Pressures
Altitude sickness
scuba diving
Boyle's Law (P and V):
Deep sea fish
Charles' Law (V and T)
Hot Air Balloons
Deflategate
Avogadro's Law (n and V)
Inhaling and Exhaling
Graham's Law
Gas Exchange in lungs
Henry's Law (solubility of gases):
Gills
Gay-Lussac's Law (P and T)
Tropical Cyclones
Airplanes flying
Cars
How a straw works
before drinking
while drinking
Pressure outside = pressure inside
The level of liquid in the straw is equal to the level of liquid outside of the straw.
When you put your mouth on the straw, you are removing air particles from the straw (by drawing them into your mouth.
This creates a vacuum inside the straw, decreasing the pressure in the straw. The pressure of the gas on top of the liquid in the cup pressing down on the liquid in the cup pushes the liquid up through the straw and into your mouth.
Pressure outside greater than inside.
P
o
P
i
Summary: A straw works because you use your mouth to create a pressure difference. By removing air particles from the straw, a vacuum is created. The pressure inside the straw is less than the pressure outside and the greater pressure outside pushes the liquid up through the straw and into your mouth.
box
The brushes on the bottom agitate the surface you're vacuuming and loosen the dirt.
There is a fan inside the box. It removes the air from the box and directs it into the bag.
When the fan removes the air from the box, the pressure inside the box is less than the pressure outside the box.
The pressure outside the box (the air on the surface of the carpet) is greater than inside the box which forces it and the dirt from the surface you're vacuuming into the box.
This dirt is then directed by the fan into the bag (or collection bin for bagless vacuums).
Prior to going into the collection bag or bin, the air passes over the motor driving the fan to cool the motor so it doesn't overheat.
How does something float?
The less dense substance floats in the more dense substance.
This is why warm air rises.
Lungs vs gills
Tropical Cyclones
Breathing
Gills
The oxygen obtained is used in the metabolic process of cellular respiration (a combustion reaction) to react oxygen with glucose to produce ATP (an energy source) with the by-products CO and H O.
2
2
Lungs
Avogadro's Law
Volume is directly proportional to moles of gas.
The autonomic nervous system sends a message to the muscles around the lungs, flattening the diaphragm and contracting the intercostal muslces. This gives the lungs space to expand.
Preparing for O intake:
2
Alveoli are full of O and capillaries surrounding them are full of CO
2
2
Diffusion - the movement from an area of higher concentration to an area of lower concentration.
The oxygen in the alveoli moves to the capillaries where there is less oxygen present and the carbon dioxide in the capillaries moves to the alveoli where there is less carbon dioxide present.
Once the alveoli are full of CO , the autonomic nervous system sends a signal to the diapraghram to ball up and the intercostal muscles to relax. This decreases the chest cavity size which decreases the volume of the lungs, forcing the CO in the lungs out (exhaling).
2
2
Gills work based on the fact that gas can be dissolved in water.
Solubility of gas:
Henry's Law
The solubility of a gas in a liquid depends on temperature, the partial pressure of the gas over the liquid, the nature of the solvent and the nature of the gas.
Countercurrent flow: Water flows over the gills in 1 direction, while blood flows through the capillaries of the gills in the opposite (or counter) direction.
This allows the blood in the capillaries to uptake the dissolved oxygen in the water passing through the gills.
The colder the temperature of the water, the more oxygen that can be dissolved.
Charles' Law:
Volume and temperature of a gas are directly proportional.
As temperature increases, volume increases.
Warm air compared to cold air has a greater volume for the same mass.
mass
volume
This makes the denominator bigger for hot air, which makes the value of density smaller.
Gay-Lussac's law:
Pressure is directly related to temperature.
Hurricanes
up to 600 miles across
strong winds spiraling inward and upward
speeds of 75 to 200 mph.
Each hurricane usually lasts for over a week
moving 10-20 miles per hour over the open ocean.
Hurricanes gather heat and energy through contact with warm ocean waters.
tropical cyclone
max wind < 39 mph = tropical depression
max wind > 39 mph = tropical storm
max sustained speed > 74 mph
Tropical cyclones form over warm ocean waters.
The warm air rises
(less dense than cooler air)
There is less pressure below because there is less air below because it rose.
Air from the sides moves into this area of lower pressure.
This is because the air from the side has a higher pressure so it is moving from an area of higher pressure to lower pressure.
The new air gets warmer and rises.
As the warm, moist air rises and cools off, it forms clouds.
The system of clouds and wind spins and grows, fed by the heat evaporating from the surface of the water.
As the storm rotates faster and faster, an eye forms in the center. This is an area of low pressure and it is very calm.
Tropical storms ususally weaken when they reach land because they are no longer being fed by heat evaporating from the ocean.
Inside vs Outside Pressure
When the denominator of a fraction gets bigger, the value of the fraction gets smaller.
3
5
3
10
0.3
0.6
3
5
3
2
0.6
1.5
Atmospheric Pressure
1 mb = 100 Pa
1000 Pa = 1 kPa
1,000 mb = 100 kPa
sea level = 101.35 kPa
14.7 psi = 101.35 kPa
101.35 kPa = 1 atm
Air is a mixture with a percent composition of O at 20%.
2
At altitude, the percent composition of oxygen in the air is the same but the overall number of molecules is less so there is a lesser amount oxygen available.
Increasing depth in water, increases the pressure. This is because in addition to the pressure from the weight of the atmopshere, there is also the pressure from the weight of the water.
Altitude sickness:
illness caused by ascent to a high altitude and the resulting shortage of oxygen, characterized chiefly by hyperventilation, nausea, exhaustion, and cerebral edema.
Dalton's Law: Each gas exerts a partial pressure and the total pressure of a mixture of gases is the sum of the partial pressure each gas exerts.
There are less oxygen molecules present so they exert a smaller partial pressure compared to sea level where there are more oxygen molecules present and they would exert a greater partial pressure.
At extremely high altitudes (25,000), the pressure of the oxygen in the lungs is lower than the pressure of oxygen in the blood.
The transfer of gases between the blood and lungs in interrupted and this can cause a loss of conciousness.
Why do you breathe faster at altitude?
There is less oxygen available so breathing faster increasing the amount of oxygen intake. This also increases the amount of carbon dioxide output.
Since carbon dioxide is acidic, it causes the blood to become more basic and the kidneys work harder to correct this acid-base imbalance.
Why do your ears pop when you increase altitude?
The ear canal is open to the outside so the pressure inside the ear canal is always the same as the pressure outside.
The Eustachian tube is closed but can be opened by moving the jaw. The pressure in this tube is the same as the pressure as the last time it was opened.
When altitude is increased, the pressure decreases. The pressure outside the Eustachian tube is lower than the pressure inside the Eustachian tube.
The higher pressure in the tube pushes on the closed tube and causes pain. This pain can be removed by equalizing the pressure inside the tube with the pressure outside.
The larger pressure on the Eustachian tube pushes and stretches the ear drum which makes it harder for you to hear.
The pop you hear is your ear drum going back to normal after the Eustachian tube is opened and the pressure inside becomes the same as outside.
Deflategate
In colder temperatures, volume decreases.
T
V
Boyle's Law
Deep Sea Fish
http://ww2.kqed.org/quest/2015/03/12/science-spotlight-fish-swim-bladders-and-boyles-law/
Most bony fish have expandable swim bladders.
Cartilagenous fish - rays, skates, sharks don't have swim bladders

Allows them to hover in 1 location without wasting energy swimming.
Pressure is increased by 1 atm (101.35 KPa) for every 10.6 m (3 ft = 1 m) underwater.
What happens if a deep sea fish is brought to the surface too quickly?
What is the relationship between P and V?
inverse
less P @ surface
more P in deep sea
Going to the surface:
P
V
fish swim bladder explodes. fish dies.
Atmospheric pressure is the force of the air in the atmosphere over a certain area as gravity pulls it to Earth's surface.
1 atm = 760 mm Hg
1 atmosphere (atm) is the average air pressure @ sea level @ 15 degrees C (59 F)
The atmospheric pressure @ the top of Mt. Denali is about half of the air pressure in Honolulu.
How does air pressure affect the weather?
Low pressure system = clouds, wind, precipitation
High pressure system = fair, calm weather
Our 5 layered atmosphere is what keeps us in our bubble and allows us to live on Earth.
Rising above Earth, the atmosphere gets thinner until it reaches space. At the top layer, atoms and molecules can escape into space.
How do airplanes fly?
Airplane wings are shaped aerodynamically to make air go over the top of the wing faster.
The pressure of the faster moving air is decreased because there is less air present at a given time.
The pressure on top of the wing is less than the pressure below the wing.
What does this do?
The push from below the wing is larger, overcomes the pressure above the wing, and it pushes the plane up and allows it to fly.
Shape of an airplane wing
Faster moving air
P
Slower moving air
P
The curve on the top of the wing is kind of like an air slide...it directs the air down which makes it go faster
Car Engine
What kind of reaction does a car engine run on?
combustion
What are the reactants and products of a combustion reaction?
organic
compound
oxygen
carbon dioxide
+
water
+
C H
8
18
O
2
+
CO
2
H O
2
+
The heat from this controlled explosion increases the volume of air, which forces the piston down into the cylinder. This opens an outlet valve, causing the piston to rise and release exhaust gases.

As the piston moves back down again, an inlet valve opens, bringing another burst of gasoline-air mixture into the chamber. The piston, whose downward stroke closed the inlet valve, now shoots back up, compressing the gas and air to repeat the cycle. The reactions of the gasoline and air are what move the piston, which turns a crankshaft that causes the wheels to rotate.



Read more: http://www.scienceclarified.com/everyday/Real-Life-Physics-Vol-2/Gas-Laws-Real-life-applications.html#ixzz44bnObsDI
When the driver pushes on the gas pedal, a throttle valve is activated which spray droplets of gas mixed with air (containing oxygen) into the engine.
(This is what it means to have a fuel-injected engine.)
The mixture goes into the cylinder of the engine, where the piston moves up, compressing the gas and air.
Is the pressure bigger or smaller?
P
The spark plug produces a spark which ignites the mixture of gas and air. (combustion reaction)
The combustion reaction produces carbon dioxide gas, water and heat. This increases the temperature of the gas.
At increased temperature, what happens to the volume of the gas?
T
V
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