The Gas Laws

Inverse Relationship

Inverse Relationship

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Pressure

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Volume

Direct Relationship

Direct

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PRESSURE AND VOLUME RELATIONSHIP

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In book - page 330

Boyle’s Law

Boyle’s Law is Pressure/Volume relationship

As Pressure increases the volume of a gas decreases…inverse relationship

FORMULAV1P1=V2P2

25 cm3 at 75 psi changes to 20 cm3 at what new pressure?

200 mls. @100 kpa will occupy what volume at 60 kpa (kilopascals)

Boyles Law

• Pressure1 x Volume1 = Pressure2 x Volume2

• For a given mass of gas at a constant temperature the volume of the gas varies inversely with the pressure.

• In an inverse relationship the product of the two variable quantities is constant.

Examples

• Deep sea diving:– Boyle’s Law– Nitrous Oxide forms in

the body when breathing high-pressured air

– The Bends: is when ascending out of water and nitrogen is diffusing out of the blood. Bubbles form.

• Breathing– Inhaling, the

diaphragm goes downward. Lungs are area of low pressure allowing air to come in.

– Exhaling, diaphragm goes upward.High pressure in lungs, air goes out.

http://science.howstuffworks.com/question101.htmThe Bends Web Site =

http://science.howstuffworks.com/lung1.htm

Diseases or Conditions that influence the machanics of

breathing Asthma: The bronchioles constrict, reducing the size of the

airways. This cuts down on the flow of air and makes the respiratory muscles work harder.

Emphysema: The lungs become stiff with fibers and become less elastic, which increases the work of the respiratory muscles.

Bronchitis: The airways become inflamed and narrower, which restricts the flow of air and increases the work of the respiratory muscles

Pneumothorax: Air in the chest cavity equalizes the pressure in the chest cavity with the outside air and causes the lungs to collapse. This is usually caused by trauma or injury. Apnea: Breathing slows or stops under a variety of conditions. There are many types of apnea, and they are usually caused by problems in the respiratory centers of the brain.

Gases diffusing in lungs

Charles’s Law

Charles Law

• Volume1 = Volume2

Temperature1 Temperature2

• The volume of a fixed mass of gas is directly proportional to its Kelvin temperature if the pressure is kept constant.

• In a direct relationship the ratio of the two quantities that change is constant.

Charles’ law Calculations

• 200 mls. Of a gas is at 1000C. The temp changes to 1500C, find the new Volume.

• 100 mls. Of a gas is at 1500C and the new volume changes to 75 mls. What is the new Temperature (in Kelvin)?

Hot Air Balloons

http://travel.howstuffworks.com/hot-air-balloon2.htm

Thermals and Migration

• How Migrating Animals Take Advantage of Thermals and UpdraftsBirds, butterflies and dragonflies all take advantage of rising currents to migrate. Think about the shape of a soaring eagle, crane, hummingbird, and monarch butterfly. All these animals are so light for their large wings that even gently rising air can push them up when their wings

are spread.

• Cumulous clouds are tell-tale signs of thermals

A thermal is a column of rising air, caused by uneven heating of the

earth

Thermal Bubbles

Temperature and Volume Law

As temperature increases volume increases as well

Charles’s law states That the volume of a Fixed mass of gas isDirectly porportional To its Kelvin temp. if The pressure is kept Constant.

Examples

• Hot air balloon:– Charles’s Law

– As the heat source increases the volume of the balloon increases allowing it to become less dense and rise.

• Thermals:– Charles’s Law

– Hot air pockets which have increased volume when heated which decrease their density. Therefore the hot air can rise.

– Thermals condense over the ocean causing cool wind to form new thermals.

– Birds use them and hot air balloons don’t like them.

Cars and Gas Lawshttp://auto.howstuffworks.com/engine3.htm

Gay-Lussac’s Law

• The pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant.

P1 = P2

T1 T2

• P1 x V1 = P2 x V2

T1 T2

• Pressure times Volume divided by temperature the new pressure times volume divided by temperature

Combined Gas Law

Boyle’s Law Problem> SOLVE!V1 = 25 mL.P1 = 100 kPaP2 = 125 kPaV2 = X (variable)

25(100) = X(125)2500 = 125X20 = X

Charles’ Law Problem > SOLVE!(Convert all temps. To Kelvin)V1 = 200 mLsT1 = 30o C. = 303o KV2 = XT2 = 100o C =373o K

200/303=X/37374600=303XX=246mls

Combined gas law-V1=150mlP1=101.3kpaT1=2730KV2=300mlP2=XT2=3230K

(150)(101.3)/323=(300)(X)/273

X= 60 kpa

Daltons LawDaltons Law

• The total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of the component gases.

• Ptotal = PA + PB + PC….

• Problem: Find the partial pressure of Nitrogen, Oxygen, other gases in the room…use today’s barometer reading.

Mt. Everest

• Physiology on Mt. Everest

• 10.67 kPa of O2 needed by humans

• Pressure on summit: 1/3 STP

Pilots and mountaineers must have supplemental oxygen when they are working in high altitudes, where oxygen is scarce.

Grahams Law

• The rate of effusion of a gas is inversely proportional to the square route of the gas’s molar mass. This relationship is also true for the diffusion of gasses.

Graham’s Law: The diffusion rate of 2 gases is inverselyProportional to the square route of the molecular gases.

Compare gas A to gas BRate of diffusion Gas A = square route Gas B Mass

Gas B Gas A MassSmaller masses diffuse fasterTo solve: Put larger mass on top, the answer = how many times faster the smaller gas diffuses.

Example: Hydrogen diffuses 4.36 times faster than fluorine.

Ideal Gas Law: R = PV Tn

Which is:

Ideal Gas Constant = Pressure x Volume

Temperature x Moles