gas laws and practical applications z.a. mason-andrews bsc. (hons), dip.ed
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Based on what is observed put forward at least two theory on gasesTRANSCRIPT
Gas Laws and Practical Applications
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
1) State the basic assumptions of kinetic theory, with reference to ideal gases
2) State properties of an ideal gas.3) Compare Real and Ideal gases
4) Calculations (Boyle’s, Charles’, Ideal Gas equation, combined gas equation, Pressure law or Constant Volume Law, Combined Gas Equation)
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Based on what is observed put forward at least two theory on gases
Matter consists of particles in Matter consists of particles in a state of constant, random a state of constant, random motionmotion. These molecules move in a straight line until they collide with the walls of the container.
In an ideal gas, these In an ideal gas, these particles occupy negligible particles occupy negligible spacespace. Volume of a gas consist mainly of empty space with molecules randomly distributed.
Forces of attraction between Forces of attraction between particles are negligibleparticles are negligible..
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Collisions between Collisions between particles are ‘perfectly’ particles are ‘perfectly’ elasticelastic. (i.e. K. Energy Before Collision =
K.Energy After Collision). This means that there are no attractive or repulsive forces involved in collisions and the total energy of the particles remain the same.
The molecules exert no force The molecules exert no force on one anotheron one another. The only interaction between molecules are their elastic collisions
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
What are the characteristics of a gas behaving most like a gas?
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Ideal GasesIdeal Gases Real GasesReal Gases
Particles occupy negligible space
Negligible forces of attraction
Perfectly elastic collisions between particles
Particles possess a definite shape and volume
Attractive forces exist between particles
Collisions not perfectly elastic, some energy converted into thermal, vibrational and rotational energy.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Under what conditions would a real gas behave like an ideal one?
Think about it....
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Gases behave ideal under conditions of high temperature and low pressure.
Increasing the temperature increases the kinetic energy of the particles, this increase in speed causes the particles to overcome the intermolecular forces of attraction between the particles and behave ideally.
Decreasing the pressure allows the particles to spread far apart form each other, allowing intermolecular forces of attraction to approach zero.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
These are results of experiments explaining the responses of gases to changes in physical quantities.
Gases are referred to as ideal gases when they obey the gas laws under all conditions
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animationsindex.htm
For an ideal gas, as Volume ↑increasesincreases Pressure ↓decreasesdecreases provided that Temperature is kept constant. (Process is isothermal).
The reverse is true if Pressure increases.
What else should be constant? And Why?Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Volume varies inversely with Pressure
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
P1V
PVPV 2211
PkV
Looks at the relationship between volume and temperature.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animationsindex.htm
For an ideal gas, as Temperature ↑increasesincreases Volume ↑increasesincreases, provided that Pressure is kept constant. (Process is isobaric).
The relationship between Temperature and Volume is directly proportional.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
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Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
• When Charles’ Law is extended to extremely low temperatures, the volume of the ideal gas should be zero.
• Does this occur?
• Explain your answer?
In reality a gas would change phase before reaching zero volume.
Temperature at which the volume of a gas would become zero if it did not condense is called absolute zero and can be found by extrapolation.
This forms the basis of a new temperature scale called absolute temperature or the Kelvin(K) which uses – 273C as the zero on the scale.
Kelvin temperature = x C + 273 Kelvin temperature must be used when Kelvin temperature must be used when
performing Gas Law calculationsperforming Gas Law calculations.Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Predict what happens to a gas when temperature increases and its volume is kept constant.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
When a gas collides with the walls of a container it exerts pressure
As temp increase particles will possess grater energy and therefore exert greater pressure
The relationship between the temperature and pressure of a gas at constant volume is called the constant volume lawconstant volume law
PP11//TT11 = = PP22//TT22 where P1 and T1 are the initial pressure and absolute temperature of a gas, and P2 and T2are its final pressure and temperature.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
This is derived from combining Boyle’s Law, Charles’ Law and the Constant Volume law or Pressure Law.
Refer to Chapter.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.
Summary activity : 1.In groups of fours produce a poem, rap, table , mind map, or use diagrams :- -To summarize the kinetic theory of gases -Describe the difference between a real and ideal gas
Include as well in your presentation :-Explanations and equations for Charles’ Law, Boyle’s Law, Constant Volume Law.-Write equations for the ideal gas and combined gas equation
Z.A. Mason-Andrews BSc. (Hons), Dip.Ed.