states of matter & gas laws

States of Matter and Gas Laws - By Aditya Abeysinghe

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States of Matter & Gas Laws


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States of MatterMatter can mainly be classified in three ways:1. Classical States of matter2. Non classical states of matter3. States classified according to the energy

content in them.Note: Although there exist different ways in

which matter can be classified, in this presentation the prominence has been given to the classical states of matter.


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On basis of energy• Low temperature

states (E.g.: Super fluids and Rydberg molecules)

• High temperature states (E.g.: Plasma (ionized gases))

• Very high energy states(E.g.: Gravitational Singularity)

Non Classical states of matter• Glass• Liquid Crystals

Classical States of matter• Solid• Liquid• Gas


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Phase changes of matter

Solid Liquid

Gas

Plasma

Melting

Freezing

Deposition

Sublimation

VaporizationCondensation

Deionization

Ionization


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Atmospheric Pressure

Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface.Atmospheric pressure is calculated in various units. The following equivalence is the most commonly used.

1 atm= 1×105 Pa= 760 mmHg= 760 torrAtmospheric pressure can simply be measured by a barometer by balancing the weight of mercury in the glass tube against the atmospheric pressure.


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Temperature

It is a measure of the thermal energy of molecules or atoms of a substance.Temperature too has many units as pressure.The relationship between these scales can be summarized as follows:F= (9/5) C +32 and K= C + 273(Always K ≥ 0)(Here F- Fahrenheit, C- Celsius, K- Kelvin)


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Gas Laws

There are six main gas laws associated with the behavior of gases:1. Boyle’s Law2. Charles's Law3. Combined Gas Law4. Avogadro's law5. Charles- Gay-Lussac’s law6. Dalton’s law of partial pressure


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Boyle’s Law

Law: If the temperature is constant for a given mass of a gas, the pressure varies inversely with volume.Applicable only if: Temperature stays constantApplicable to:1. Ideal gases at any temperature2. Real gases which behave approximately as

ideal gases specially at high temperatures.


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Graphs of Boyle’s lawP

V

PV=kP=k(1/V)

P

1/v

PV

P

PV= kLog(PV)=Log k

Log P + Log V=Log kLog P= Log k- Log V

Log P= -Log V+ Log k

Y = -mx + c

Log P

Log V

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Effect of external factors on a system obeying Boyle’s Law

1. Effect of temperature 2. Effect of massTemperature increases in the direction of the arrow head keeping the PV product constant

P

V

P

V

Mass increases in the direction of the arrow head keeping the PV product constant

Temperature increases Mass increases PV PV

P PStates of Matter and Gas Laws - By Aditya Abeysinghe


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Charles's LawLaw: If the pressure is kept constant for a given mass of a gas the volume varies directly with the absolute temperature.Applicable only if: Pressure stays constantApplicable to:1. Ideal gases at any temperature2. Real gases which behave approximately as

ideal gases specially at low pressures.

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Graphs of Charles’s Law1. With absolute (K)

temperatureV

T(K)

2. With Celsius temperature

‘Extrapolation’ shows that every gas would achieve zero volume at -273.15 0C

-273.15 0C

V

T(0C)



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Effect of external factors on a system obeying Charles’s Law

1. Effect of pressure 2. Effect of mass

V

T(K)

V

T(K)Pressure increases in the direction of the arrow head

Mass increases in the direction of the arrow head


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Combined Gas Law

PV T

k

When P is maintained constant,V/T = k. Therefore the system obeys the Charles’s law.

When T is maintained constant, PV = k. Therefore the system obeys the Boyle’s law.


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Avogadro’s law

Law: Equal volumes of gases at the same temperature and same pressure contain the same no. of molecules/atoms.Modified law: Equal volumes of gases at the same temperature and same pressure contain the same no. of moles.(Since no. of moles= no. of atoms or molecules × Avogadro Number)


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Charles-Gay Lussac LawThe second form of the Charles's law describes that there exist a direct relationship between the pressure and the absolute temperature of a system if the volume is kept constant.Then, P/T = k.

This can also be obtained from the combined gas law by keeping V constant.


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Dalton’s Law of Partial Pressures

Law: The pressure of a mixture of gases is the sum of the partial pressures of its parts.Therefore, a gas mixture which holds O2 and N2 has a total pressure of :

Ptotal = Poxygen + Phydrogen

In a similar way the unsaturated gas pressure of a gas containing vapor can be calculated.


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General/Ideal gas equationPV= nRT

(R- Universal Gas Constant)i. When mass and temperature are constant, n and T become constant. Since

R is also a constant for any gas, PV = k. Thus, when the mass and the temperature are constant, from the above equation, the system obeys Boyle’s Law.

ii. When mass and pressure are constant, P ,R and T are constant. Thus V/T = k or the system, from the above equation, obeys Charles’s Law.

iii. When mass and volume are constant, V, n and R are constant. Thus, from the above equation, P/T is a constant. P/T = k. Therefore, the system obeys Charles- Gay Lussac (Charles’s 2nd ) Law.

iv. When P, V and T are constant, The no. of moles, molecules or atoms for a particular gas is a constant. Thus, the no. of moles, molecules or atoms of one gas is equal to that of another gas at the same temperature, same volume and under same pressure. Thus the system obeys Avogadro’s Law.

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About the Universal Gas ConstantUniversal gas constant is a value/expression that is independent of the used gas and other physical factors (such as Pressure, Temperature, Volume…).Its value is 8.314J/(mol.K)It also displays a relationship with the Boltzmann Constant as ,Boltzmann Constant = Universal Gas Constant/ No. of molecules or atoms in the gas

States of Matter and Gas Laws – By Aditya Abeysinghe


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Summarizing it up!!!!

Ideal gas equationPV =nRT

Gas law problems

Combined gas equation (PV)/T = k

Charles-Gay lussac’s law

P/T = k

Charles’s lawV/T = k

Boyle’s lawPV= k

When either mass or the no. of moles are given

When the mass of a given gas is constant

When T1 = T2 When P1= P2When V1= V2

states of matter & gas laws

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