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OB: Practice phase concepts: cooling and heating curves, phase diagrams, pressure conversions, table H problems.

OB: Practice phase concepts: cooling and heating curves, phase diagrams, pressure conversions, table H problems. Take out NEW reference tables. Recycle the old ones NOW.

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OB: Practice phase concepts: cooling and heating curves, phase diagrams, pressure conversions, table H problems.

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  1. OB: Practice phase concepts: cooling and heating curves, phase diagrams, pressure conversions, table H problems. Take out NEW reference tables. Recycle the old ones NOW.

  2. Draw the Cooling curve for cobalt. On the same graph, draw the heating curve for cadmium. Titles, axis labels and scales, be big. 3200 2400 1600 800 Temp Kelvin Energy added (or removed) at constant rate over time

  3. Draw the heating curve for cobalt. On the same graph, draw the cooling curve for cadmium. Titles, axis labels and scales, be big. 3200 2400 1600 800 Cadmium BP: 1040 KFP: 594 K Temp Kelvin Cobalt BP: 3200 K FP: 1768 K Energy added (or removed) at constant rate over time

  4. Why are the flat lines different lengths on every heating curve (and every cooling curve)? BC represents the melting of ice. It takes for water, 334 Joules of energy to melt one gram of ice from solid to liquid without increasing the temperature. It’s called the heat of fusion For water: HF = 334 J/gram DE represents the boiling of water into steam. It takes for water, 2260 Joules of energy to vaporize one gram of water to steam without increasing the temperature. It’s called the heat of vaporization For water: HV= 2260 J/gram The phase change from liquid to gas is MUCH more energetic than melting solid to liquid. For water, it’s nearly 7X more!

  5. A phase diagram shows one substance’s range of phases through temperature and pressures. Below is the phase diagram for water. Special Points on this graph: Tm: normal melting point Tb: normal boiling point TP: triple point CP: critical point

  6. Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into each top. AIR PRESSURE101.3 kPa Start pressure inside flasks the same Warm up the room to 25⁰C What is pressure inside each flask?

  7. Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into each top. AIR PRESSURE101.3 kPa Start pressure inside flasks the same 25⁰C Vapor Pressure ethanol @ 25⁰C is about 8 kPa Vapor pressure propanone @ 25⁰C is about 31 kPa What if we heat it up to 65⁰C next???

  8. Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into each top. AIR PRESSURE101.3 kPa Start pressure inside flasks the same 65⁰C Vapor Pressure ethanol @ 65⁰C is about 60 kPa Vapor pressure propanone @ 65⁰C is about 135 kPa KABOOM!

  9. Properties of SOLIDS, LIQUIDS, and GASES Compared SOLIDS Particles are strongly attracted to each other, other than some vibration there is nearly no movement of the atoms or molecules, they have a rigid or lattice arrangement of the particles, they keep their shapes and volumes, they do not take the shape of their containers. Solids cannot be compressed very much because the particles are very close together. Because of this most solids have a high density compared to their liquids or gases. When energy or heat is added, the particles will vibrate more, which often makes solids expand when heated. Particles in solids have the lowest kinetic energy. Give solids enough energy (at the proper pressure) and they will vibrate so much that they break apart and turn into ....

  10. LIQUIDS Particles have some attraction to each other but not enough to make them stuck. Liquids flow over themselves, the particles are in constant random motion. Liquids do not have a definite shape which means they take the shape of the container you put them in. If you spill liquids, the force of gravity spreads them out quite well. The hotter liquids get when you add energy, the faster the particles move, and liquids too expand slightly when heated. Liquids are dense as well, but usually not as dense as solids are. Heat a liquid enough, the particles move so much that they turn into...

  11. GASES There is virtually no attractive or repulsive force between the particles. The particles move in straight lines and very fast. They collide with other particles all of the time. These collisions will cause gas (or air) pressure. Gases take the shape of the container that you put them in. Any amount of a gas will fill any container that you put it in. The collisions are considered to be elastic, meaning there is no loss of kinetic energy due to the collisions. Heated gases make the particles move faster and have more collisions, causing expansion if possible, or greater pressures if contained in a definite volume. Gas Particles have the highest kinetic energy. Gases have very low density.

  12. Gas Pressure is measured with different pressure units, all on table A. Let’s add mm Hg now to the new tables. 1.0 atm = 760. mm Hg = 101.3 kPa = 14.7 psi Today’s pressure is exactly 1.14 atm. Convert that to mm Hg, and kPa right now…

  13. This slide left intentionally blank, you know why…

  14. 1.14 atm1 760. Mm Hg1.0 atm X = 866 mm Hg (3 SF) 1.14 atm1 101.3 kPa1.0 atm X = 115 kPa (3 SF)

  15. 1st At any one temperature, say 65°C,ethanonic acid has the lowest vapor pressure, propanone the highest. WHY??? Each liquid, these 4 included, at any one temperature will evaporate to a certain degree. How much this happens is connected first to the temperature, and then, to how strong the inter-molecular attractions the molecules have for each other. At 65°C Propanone has the lowest intermolecular attraction and therefore the highest vapor pressure. Ethanoic acid has strong intermolecular attraction, so low vapor pressure.

  16. Put a small note onto your reference tables if you want to now. Propanone has the highest vapor pressure of these four, at any temperature, because it has the weakest intermolecular attractions for itself. Ethanoic acid has the lowest vapor pressure of these four, at any temp. because it has the strongest intermolecular attractions for itself.

  17. Heating curve for an unknown substance BP in FP K Energy being added at a constant rate over time.

  18. Heating curve for an unknown substance PE D BP in FP E From BC there is no change in temperature. From DE there is no change in temperature. Ergo: Kinetic Energy is steady. Potential Energy must increase there. K PE B C Energy being added at a constant rate over time.

  19. Heating curve for an unknown substance D BP in FP E Temp KE K From CD there is an increase in temperature. That means Kinetic Energy Increases too If kinetic energy is changing, Potential energy is steady (doin’ nutin’) B C Energy being added at a constant rate over time.

  20. Kinetic Energy & Temperature are the same thing, sort of. The greater the KE, the greater the temp. Lower temp = lower KE Temp + Kinetic energy are like Michael Jackson’s hand & his glove. What ever one does, so does the other. The other energy, Potential Energy, is used when there is no change in the kinetic energy. It’s for those phase change times. If kinetic energy (temp) is changing, potential energy is steady. In a phase change kinetic energy is steady (so is temp), then the PE is going up in a heating curve, or the PE is going down in a cooling curve.

  21. Over break, make sure you read through all the diaries that you missed. Complete all through the phases diary. In January we begin thermochemistry. It’s a bunch of math, fun labs, and you’ll want to get an amazing tattoo of the formula. Q = mC∆T

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