Intermolecular forces Part 2 Properties of liquids
Description: Intermolecular forces Part 2 Properties of liquids Vaporization Imagine a large tympanic drum with sand particles on the drumhead. As the drum is hit, the sand particles bounce. As the drum is hit harder and harder, the sand particles
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slide1. Intermolecular forces Part 2 Properties of liquids<br>
slide2. Vaporization Imagine a large tympanic drum with sand particles on the drumhead. As the drum is hit, the sand particles bounce. As the drum is hit harder and harder, the sand particles bounce higher and higher. Finally the drum is hit so hard that some of the sand particles bounce into the air and are blown away by the breeze.<br>
slide4. www.britannica.com/ebi/article-206259<br>
slide5. Wheat and chaff https://youtu.be/G_gfgxkZryM<br>
slide6. Wheat & chaff - 2 https://youtu.be/QbMWvAnUFz0<br>
slide7. Vaporization (continued) This is what happens when a liquid evaporates. The liquid is bombarded with air molecules that transfer energy to the surface molecules. At some point, a few of the surface molecules gain enough energy to escape.<br>
slide8. Vaporization (continued) Recall that temperature is a measure of the average kinetic energy of a substance.<br>
slide9. Vaporization (continued) Since the molecules with the highest energy escape, the average kinetic energy of the molecules left in the liquid drops. This is why evaporation is a cooling process.<br>
slide10. Vaporization (continued) For example . . . Consider test scores . . . 99
99
98
87
84
78
75 average
620/7 = 88.6 99
99
98
87
84
78 new
75 average
620/7 = 88.6
324/4 = 81 Highest scores
removed<br>
slide11. Crack the whip playground https://youtu.be/dDk83PwYxKQ
Notice how the one at the end cannot hang on and flies off. There is too much energy, too little strength to hold on.<br>
slide12. Evaporation can occur
at any temperature<br>
slide13. vaporization
Liquid + heat vapor
Heat is
latent heat of vaporization (energy/grams)
molar enthalpy (heat) of vaporization (energy/mol) Vaporization (continued) Vaporization is always an endothermic process<br>
slide14. Vaporization (continued) In the reverse process, the molecules lose energy as they collide. When they slow down, the intermolecular forces become more effective at holding the particles together. condensation
Vapor liquid + heat
Condensation is an exothermic process.<br>
slide15. Vaporization is a
cooling process! Condensation is a
heating process!!<br>
slide16. Vapor Pressure Leave a glass of water out – it evaporates Leave a bottle of perfume open – it evaporates. Take a closed bottle of perfume and remove the top. You will notice a rush of perfume odor. Why is there perfume ready to come out of the bottle when the lid is closed?<br>
slide17. Vapor Pressure Liquid + heat  vapor Double headed arrow has
special meaning. Dynamic Equilibrium Important concept!!<br>
slide18. Vapor Pressure Liquid molecules gain energy  vapor state
liquid + heat  vapor
This continues allowing the number of vapor molecules to increase.
Then vapor molecules collide, losing energy  liquid state
vapor  liquid + heat<br>
slide19. Vapor Pressure For every liquid molecule evaporating to vapor, a vapor molecule condenses to liquid. When the rates of evaporation and condensation are equal a dynamic equilibrium has been reached. This means the space above the liquid is saturated with the vapor. It can hold no more vapor, just like a sponge that can hold only so much water before it begins to drip.<br>
slide20. Vapor Pressure Thus . . . the  has double meaning . . .
Dynamic equilibrium
Saturation. Vapor pressure is a measure of the strength of intermolecular forces. The higher the pressure the more molecules are in the vapor state, the weaker the forces.<br>
slide21. Vapor pressure Equilibrium Vapor pressure =
The Pressure of the Vapor at Equilibrium Explaining Vapor Pressure on the Molecular Level
Dynamic Equilibrium: the point when as many molecules escape the surface as strike the surface.
Vapor pressure is the pressure exerted when the liquid and vapor are in dynamic equilibrium.<br>
slide22. Vapor Pressure & Boiling Point As a liquid (we’ll talk about water here) is heated small bubbles of dissolved gases appear. The water molecules begin moving faster and faster, increasing in kinetic energy<br>
slide23. Slo-mo water boiling https://youtu.be/0xcxumccf8Q
https://youtu.be/5sb9x2BcuEE<br>
slide24. Vapor Pressure & Boiling Point The water molecules eventually have so much kinetic energy they cannot hold on to each other.
The molecules try to fly apart pushing against the pressure directed inward caused by the atmospheric pressure. Atmospheric pressure<br>
slide25. Vapor Pressure & Boiling Point Eventually the vapor pressure equals the atmospheric pressure.
A bubble of water vapor forms. Atmospheric pressure<br>
slide26. Vapor Pressure & Boiling Point Atmospheric pressure Water
Vapor
pressure Now is when the boiling point temperature is taken.<br>
slide27. https://youtu.be/Ag4lLUXKuSM<br>
slide28. Consider this graph . . .<br>
slide29. Notice the pressure at which normal boiling point is measured<br>
slide30. Every point along the line is the boiling point at that pressure. This pressure This temperature This point
on the line
is the boiling
point at this
pressure<br>
slide2. Vaporization Imagine a large tympanic drum with sand particles on the drumhead. As the drum is hit, the sand particles bounce. As the drum is hit harder and harder, the sand particles bounce higher and higher. Finally the drum is hit so hard that some of the sand particles bounce into the air and are blown away by the breeze.<br>
slide4. www.britannica.com/ebi/article-206259<br>
slide5. Wheat and chaff https://youtu.be/G_gfgxkZryM<br>
slide6. Wheat & chaff - 2 https://youtu.be/QbMWvAnUFz0<br>
slide7. Vaporization (continued) This is what happens when a liquid evaporates. The liquid is bombarded with air molecules that transfer energy to the surface molecules. At some point, a few of the surface molecules gain enough energy to escape.<br>
slide8. Vaporization (continued) Recall that temperature is a measure of the average kinetic energy of a substance.<br>
slide9. Vaporization (continued) Since the molecules with the highest energy escape, the average kinetic energy of the molecules left in the liquid drops. This is why evaporation is a cooling process.<br>
slide10. Vaporization (continued) For example . . . Consider test scores . . . 99
99
98
87
84
78
75 average
620/7 = 88.6 99
99
98
87
84
78 new
75 average
620/7 = 88.6
324/4 = 81 Highest scores
removed<br>
slide11. Crack the whip playground https://youtu.be/dDk83PwYxKQ
Notice how the one at the end cannot hang on and flies off. There is too much energy, too little strength to hold on.<br>
slide12. Evaporation can occur
at any temperature<br>
slide13. vaporization
Liquid + heat vapor
Heat is
latent heat of vaporization (energy/grams)
molar enthalpy (heat) of vaporization (energy/mol) Vaporization (continued) Vaporization is always an endothermic process<br>
slide14. Vaporization (continued) In the reverse process, the molecules lose energy as they collide. When they slow down, the intermolecular forces become more effective at holding the particles together. condensation
Vapor liquid + heat
Condensation is an exothermic process.<br>
slide15. Vaporization is a
cooling process! Condensation is a
heating process!!<br>
slide16. Vapor Pressure Leave a glass of water out – it evaporates Leave a bottle of perfume open – it evaporates. Take a closed bottle of perfume and remove the top. You will notice a rush of perfume odor. Why is there perfume ready to come out of the bottle when the lid is closed?<br>
slide17. Vapor Pressure Liquid + heat  vapor Double headed arrow has
special meaning. Dynamic Equilibrium Important concept!!<br>
slide18. Vapor Pressure Liquid molecules gain energy  vapor state
liquid + heat  vapor
This continues allowing the number of vapor molecules to increase.
Then vapor molecules collide, losing energy  liquid state
vapor  liquid + heat<br>
slide19. Vapor Pressure For every liquid molecule evaporating to vapor, a vapor molecule condenses to liquid. When the rates of evaporation and condensation are equal a dynamic equilibrium has been reached. This means the space above the liquid is saturated with the vapor. It can hold no more vapor, just like a sponge that can hold only so much water before it begins to drip.<br>
slide20. Vapor Pressure Thus . . . the  has double meaning . . .
Dynamic equilibrium
Saturation. Vapor pressure is a measure of the strength of intermolecular forces. The higher the pressure the more molecules are in the vapor state, the weaker the forces.<br>
slide21. Vapor pressure Equilibrium Vapor pressure =
The Pressure of the Vapor at Equilibrium Explaining Vapor Pressure on the Molecular Level
Dynamic Equilibrium: the point when as many molecules escape the surface as strike the surface.
Vapor pressure is the pressure exerted when the liquid and vapor are in dynamic equilibrium.<br>
slide22. Vapor Pressure & Boiling Point As a liquid (we’ll talk about water here) is heated small bubbles of dissolved gases appear. The water molecules begin moving faster and faster, increasing in kinetic energy<br>
slide23. Slo-mo water boiling https://youtu.be/0xcxumccf8Q
https://youtu.be/5sb9x2BcuEE<br>
slide24. Vapor Pressure & Boiling Point The water molecules eventually have so much kinetic energy they cannot hold on to each other.
The molecules try to fly apart pushing against the pressure directed inward caused by the atmospheric pressure. Atmospheric pressure<br>
slide25. Vapor Pressure & Boiling Point Eventually the vapor pressure equals the atmospheric pressure.
A bubble of water vapor forms. Atmospheric pressure<br>
slide26. Vapor Pressure & Boiling Point Atmospheric pressure Water
Vapor
pressure Now is when the boiling point temperature is taken.<br>
slide27. https://youtu.be/Ag4lLUXKuSM<br>
slide28. Consider this graph . . .<br>
slide29. Notice the pressure at which normal boiling point is measured<br>
slide30. Every point along the line is the boiling point at that pressure. This pressure This temperature This point
on the line
is the boiling
point at this
pressure<br>