Chapter 3 - Properties of fluids.ppt
- 1. How do we use the Kinetic Molecular Theory to explain the behavior of gases? Introduction to Gases https://www.sisd.net/cms/lib/TX01001452/Centricity/Domain/382/Intro%20to%20Gases% 20and%20Gas%20Laws.ppt
- 2. States of Matter •There are two main factors determine the state: •The forces (inter/intramolecular) holding particles together •The kinetic energy present (the energy an object possesses due to its motion of the particles) •KE tends to ‘pull’ particles apart Atkins, P.W.; Jones, Loretta Chemistry Molecules, Matter and Change 4th Ed. . July 2000
- 3. Kinetic Energy , States of Matter & Temperature • Gases tend to have more higher kinetic energy in their molecules due to weak bonding as compare to solid and liquid. • On increase the temperature, the gas particles move faster, and thus kinetic energy increases in the system.
- 4. Characteristics of Gases • Gases can expand to fill any container to any shape. • They have random motion, no attraction in their particles • Gases are fluids (like liquids). • There is no attraction in their molecules/atoms. • Gases have very low densities. • no volume = lots of empty space
- 5. Characteristics of Gases • Gases can be compressed. • no volume = lots of empty space, • how air conditioner works? Hint: Compressor role? • Gases undergo diffusion & effusion (across a barrier with small holes). • random motion • How perfume molecules spread, from high concentration to low concentration.
- 6. Kinetic Molecular Theory of ‘Ideal’ Gases • Particles in an ideal gas… • They have no volume or no shape. • They have elastic collisions (ie. billiard ball/snooker particles exchange energy with each other, but total KE is conserved in the system. • They have constant, random, straight-line motion, no circular motion. • They don’t attract or repel each other, no attraction between molecules. • They have avg. KE directly related to temperature, it is directly proportional, if one parameter increases then other one will also increase. Atkins, P.W.; Jones, Loretta Chemistry Molecules, Matter and Change 4th Ed. . July 2000
- 7. Real Gases • The behavior of particles in a REAL gas condition • They have their own volume • They attract each other (intermolecular forces) • Gas behavior is found most ideal… • at low pressures • at high temperatures (high KE)
- 8. Real Gases •At STP, molecules of gas are moving fast and are very far apart, making their intermolecular forces and volumes insignificant, so assumptions of an ideal gas are valid under normal temp/pressure conditions. BUT… •at high pressures: gas molecules are pushed closer together, and their interactions with each other become more significant due to volume •at low temperatures: gas molecules move slower due to KE and intermolecular forces are no longer negligible
- 9. Pressure area force pressure Which shoes create the most pressure?
- 10. Atmospheric Pressure •The gas molecules in the atmosphere are pulled toward Earth due to gravity, exerting pressure •Ears ‘pop’ in an airplane or at high mountain or high rise building/skycrappers?
- 11. Pressure • Barometer • measures atmospheric pressure Mercury Barometer Atkins, P.W.; Jones, Loretta Chemistry Molecules, Matter and Change 4th Ed. . July 2000
- 12. Units of Pressure •At Standard Atmospheric Pressure (SAP) 101.325 kPa (kilopascal) 1 atm (atmosphere) 760 mm Hg (millimeter Hg) 760 torr 14.7 psi (pounds per square inch) 2 m N kPa
- 13. Temperature: The Kelvin Scale • Always use absolute temperature (Kelvin) when working with gases. ºC K -273 0 100 0 273 373 273 K C K = ºC + 273
- 14. Kelvin and Absolute Zero • Scottish physicist Lord Kelvin suggested that -273oC (0K) was the temperature at which the motion particles within a gas approaches zero. And thus, so does volume) • Absolute Zero: http://www.youtube.com/watch?v=JHXxPnmyDbk • Comparing the Celsius and Kelvin Scale: http://www.youtube.com/watch?v=-G9FdNqUVBQ
- 15. Kelvin Scale vs Celsius Scale
- 16. Converting between Kelvin and Celsius a) 0oC =_____K b) 100oC= _____K c) 25oC =______K d) -12oC = ______K e) -273K = ______oC f) 23.5K = ______oC g) 373.2K= ______oC 273 K C K = ºC + 273
- 17. Boyle’s, Charles’ and Gay-Lussac’s Laws relating T, P and/or V the combined gas law. The Gas Laws
- 18. 1. Intro to Boyle’s Law •Suppose that you hold the syringe by your hand and there should be no leak from the cylinder or body of syringe, no gas can release. Now push down on the piston of the syringe in and out. Is it any changes in the volume inside the syringe? Do you feel pressure of the gas is exerting in the syringe during the pressing of piston?
- 19. 1. Boyle’s Law Remember : Example of AC, how the compressor works
- 20. 1. Boyle’s Law •The pressure and volume of a gas are inversely proportional (as one increases, the other decreases, and vice versa •at constant temp P V General chemistry- Principles, patterns and Applications. Bruce Averill, Strategic Energy Security Solutions. Patricia Eldredge, R.H. Hand, LLC ISBN 13: 9781453322307. Saylor Foundation. Pages: 186-222
- 21. 1. Boyle’s Law Boyle’s Law leads to the mathematical expression: *Assuming temp is constant P1V1=P2V2 Where P1 represents the initial pressure V1 represents the initial volume, And P2 represents the final pressure V2 represents the final volume
- 22. Example Problem: A hot balloon having a vol of 4000 L at pressure of 100.0 kPa rises to an altitude of 2000 m, where the atm pres is found to be 50.2 kPa. There is no change in the temp and the amount of gas, find the balloon’s final vol.
- 23. V T 2. Charles’ Law • The volume and absolute temperature (K) of a gas are directly proportional (an increase in temp leads to an increase in volume) • at constant mass & pressure https://www.sisd.net/cms/lib/TX01001452/Centricity/Domain/382/Intro%20to%20Gases%20 and%20Gas%20Laws.ppt
- 24. 2. Charles’ Law
- 25. 2. Charles’ Law • Charles’ Law leads to the mathematical expression: *Assuming pressure remains constant
- 26. 2. Intro to Charles’ Law • Imagine that you put a balloon filled with gas in liquid nitrogen What is happening to the temperature of the gas in the balloon? What will happen to the volume of the balloon?
- 27. Example Problem: John filled the balloon with helium gas, having volume of 3.0 L in an air- conditioned room at 300 K. Then, he took the balloon outdoors on a warm day where the volume change or expands to 3.25 L. Suppose the pres and the vol of gas is constant, find the air temperature? A volley ball is inflated to a vol of 50 L of air at 30 oC. During the afternoon, the volume increases by 2 L. Find the new temperature outside?
- 28. 3. Intro to Gay-Lussac’s Law • Suppose you have a balloon that it has a fixed volume. • You heat the balloon. What is change in the temp of gas inside the balloon? Any change will happen to the pressure, the gas is exerting on the balloon?
- 29. P T 3. Gay-Lussac’s Law • The pressure and absolute temperature (K) of a gas are directly proportional (as temperature rises, so does pressure) • at constant mass & volume
- 30. 2. Gay-Lussac’s Law • Gay-Lussac’s Law leads to the mathematical expression: *Assuming volume remains constant Egg in a bottle to show Gay-Lussac's Law: T & P relationship: http://www.youtube.com/watch?v=r_JnUBk1JPQ
- 31. Example Problem: The pressure of the oxygen gas inside a canister with a fixed volume is 5.0atm at 15oC. What is the pressure of the oxygen gas inside the canister if the temperature changes to 263K? Assume the amount of gas remains constant. The pressure of a gas in a sealed canister is 350.0kPa at a room temperature of 15oC. The canister is placed in a refrigerator that drops the temperature of the gas by 20K. What is the new pressure in the canister?
- 32. 4. Combined Gas Law P1V1 T1 = P2V2 T2 By combining Boyle’s, Charles’ and Gay Lussac’s Laws, the following equation is derived: A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.
- 33. References 1. General chemistry- Principles, patterns and Applications. Bruce Averill, Strategic Energy Security Solutions. Patricia Eldredge, R.H. Hand, LLC ISBN 13: 9781453322307. Saylor Foundation. Pages: 186- 222 2. East, T.D and McConkey, A (1996), Applied Thermodynamics for Engineering Technologists.5thEd,Longman. 3. Atkins, P.W.; Jones, Loretta Chemistry Molecules, Matter and Change 4th Ed. . July 2000 Useful link: http://readinglists.central-lancashire.ac.uk/index