1. Hope You Enjoyed Your Break!!
Chapter 13 continued…
Hope You Enjoyed Your Break!!

2. Review…. Answer the following questions on the paper I gave you…
1) Why does a cup of hot coffee become cold after sitting out on a table for a couple of hours?
2) What instrument is used to measure atmospheric pressure?
3) Convert 500 mm Hg to atm’s and Kpa
4) What assumption of the KMT is incorrect?
5) What factors determine the physical properties of a liquid?

3. Nature of Liquids: Evaporation
Closed vs. Open Container
Vapor Pressure: measure of the force exerted by a gas above a liquid.
A terrarium is a container which is designed to hold small plants and animals in controlled conditions. The closed nature of a terrarium creates an environment which is easy to control, allowing people to simulate everything from the desert to the rainforest.

4. Vapor Pressure
Dynamic Equilibrium: the rate of evaporation of liquid equals to rate of condensation of a vapor
-vapor pressure is constant at equilibrium
-condensation is a sign that equilibrium has occurred.

5. Animations
Manometer and Pressure vs. Temp

6. Vapor Pressure and Temperature
As temperature increases, vapor pressure increases
Increased temp
more molecules with enough K.E escape liquid
Higher frequency of evaporated molecules hitting wall of container
Increased vapor Pressure

7. Boiling Point Boiling occurs
At a specific temperature when the vapor pressure of the liquid equals atmospheric pressure.
Occurs when a liquid is heated and bubbles of vapor form.
Evaporation can occur at any temperature, boiling point only occurs for a specific temperature for a liquid.

8. Boiling Point : Different Elevations
Why does it take longer to cook food in water at high altitudes? Atmospheric pressure decreases with higher elevation; so water will boil at a lower temperature so food cooks slower Why does food take less time to cook in a pressure cooker The pressure in a pressure cooker can be greater than atmospheric pressure so the water can boiler at a higher temperature and food will cook faster.

10. Hand Boiler
How does the hand boiler shown to you in the front of the room work?
In a closed container, as the temperature goes up, so does the pressure. As the temperature increases, the molecules of gas in the container move faster, which increases the pressure. As the pressure increases in one of the chambers, the liquid will be pushed into the other one. alcohol vapor is forced up the tube, causing the liquid in the top bulb to appear to "boil."

11. Boiling Point: Different Liquids
Normal B.Point: The b.p. of a liquid at a pressure of kpa
Normal b.p. of water is 100 degrees Celsius
Different liquids have different boiling points because

12. 13.3 The Nature of Solids WHAT IS A SOLID?
The general properties of solids reflect the orderly arrangement and the fixed locations of their particles.
Particles in a solid are packed tightly together
When you heat a solid, the particles vibrate more rapidly and KE increases. Eventually the solid melts.
Melting Point: is the temperature at which a solid changes into a liquid.

13. Solids
Most solids are in the form of a crystal, an orderly, repeating, three-dimensional pattern of atoms.
The shape of the crystal reflects the arrangement of particles within the solid
The smallest group of particles within a crystal that retains the geometric shape of the crystal is known as a unit cell.

14. Crystal Systems

15. Allotropes What are a diamond, graphite and a buckyball all made from?
Allotrope: two or more different molecular forms of the same element in the same physical state.
Diamond: each carbon is strongly bonded to four others, rigid and compact
Graphite: carbon atoms linked in widely spaced layers of hexagonal ( six sided) arrays
Bucky Ball: buckminsterfullerene, 60 carbon atoms form a hollow sphere, (similar to a soccer ball shape)

16. Amorphous Solids Amorphous solid: lacks an ordered internal structure.
Examples are rubber, plastic, asphalt, glass.
When a crystalline solid breaks, the piece that broke off has same surface angles as original piece.
When a non-crystalline solid breaks, the pieces that break off have irregular angles and jagged edges.
Glass softens with temperature which is vital to glass blowers. The structure of glass in in between those of a crystalline solid and a liquid. Glass does not melt at definite temperatures, they can get soft and then molded into different shapes.

17. Changes of State
Sublimation: solid converts to a vapor. (skips liquid state)
Occurs in solids with vapor pressures that exceed atmospheric pressure at or near room temperature.
Sublimation can occur because solids can have a vapor pressure as well as liquids.
Examples:
Dry Ice (solid carbon dioxide)
Air Fresheners

18. Freeze Drying This is how they make astronaut ice cream!
Sublimation is used for freeze drying: a method of removing water from food
Freeze-drying is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. (like a trip to the moon!)
Freeze-drying works by freezing the material and then reducing the surrounding pressure and adding enough heat to allow the frozen water in the material to sublime directly from the solid phase to gas.
This is how they make astronaut ice cream!

19. Phase Changes

20. Heating Curve Illustrated

21. Any temperature and pressure combination not on a curve represents a single phase.
Phase diagram: plot of pressure vs. Temperature summarizing all equilibria between phases.
Given a temperature and pressure, phase diagrams tell us which phase will exist.

22. Phase Diagram Features of a phase diagram:
Triple point: temperature and pressure at which all three phases (solid,liquid,gas) are in equilibrium.
Vapor-pressure curve: generally as pressure increases, temperature increases.
Melting point curve: as pressure increases, the solid phase is favored if the solid is more dense than the liquid. The curve will lean away from the more dense phase.
Normal melting point: melting point at 1 atm.

23. The Phase Diagrams of H2O and CO2