Liquids and Solids

1. Liquids and Solids Chapter 12

2. Properties of Liquids and the KMT • Liquid- can be described as a form of matter that had definite volume and takes the shape of its container • Fluid- A substance that can flow and therefore takes the shape of its container

3. 6 properties of liquids • Relatively high density- this is a result of the close arrangement of particles • Relative incompressibility- liquids are much less compressible than gases because the particles are more closely packed together • Ability to diffuse- occurs because of the constant random motion of particles

4. Surface tension- a force that tends to pull adjacent parts of a liquid’s surface together • Capillary Action- the attraction of the surface of a liquid to the surface of a solid (root pressure in plants) • Evaporation- a process by which particles escape and enter the gas phase from a non boiling liquid.

5. Vaporization – is the process by which a liquid or solid changes into a gas. Evaporation is a form of vaporization. 2 examples - perfume & fresh water from oceans

8. Introduction to Solids • When a liquid is cooled, the average energy of its particles decreases • The physical change of a liquid to a solid by removal of heat is called freezing (solidification) • All liquids freeze…but not necessarily at temperatures you normally encounter.

9. Formation of Solids • Properties of solids and the KMT • Definite shape and volume-particles are packed closely together compared to liquids and gases. • Definite melting point- the temperature at which a solid becomes a liquid • High density and low compressibility • Low rate of diffusion

10. 2 Types of Solids • Crystalline solids- consists of crystals in which the particles are arranged in an orderly, geometric, repeating pattern • Amorphous solids -amorphous means “without shape” -fiberglass, optical fibers, some plastics and glass are amorphous solids

12. Concept Questions • Describe the liquid state according to the KMT. • List the properties of liquids. • Why do liquids in a test tube form a meniscus? • Compare vaporization and evaporation.

13. Concept Questions • Describe the solid state according to the KMT. • What is the difference between amorphous solid and a crystalline solid? • Why do solids have definite volume, high density and extremely low rates of diffusion?

14. Changes of State Section 12.3

15. 6 phase changes • Solid  liquid melting • Solid  gas sublimation • Liquid  solid freezing • Liquid  gas vaporization • Gas  liquid condensation • Gas  solid deposition

17. Equilibrium- a dynamic condition in which 2 opposing changes occur at equal rates in a closed system • Phase- any part of a system that has uniform composition and properties

18. An equilibrium equation • Liquid + heat energy  vapor • Vaporization/evaporation • Vapor  liquid + heat energy • Condensation • Liquid + heat energy  vapor • Liquid-vapor equilibrium

19. What state of matter is (a)? What about (b)? _________________ is occurring at (c)?

20. Le Chatelier’s Principle • A system will remain at equilibrium until something occurs to change this condition • Le Chatelier’s principle- when a system is disturbed by application of a stress, it attains a new equilibrium position that minimizes stress • Stress- any change in concentration, pressure, or temperature

21. Let’s look again at our equilibrium system… Liquid + heat energy  vapor • Which direction is the endothermic reaction? • Which direction is the exothermic direction?

22. Equilibrium Shifts

23. Volatile and Nonvolatile Liquids • Volatile liquids- liquids that evaporate readily • Nonvolatile liquids- evaporate slowly, have strong attractive forces between particles

24. Boiling • Boiling point-conversion of a liquid to a vapor within the liquid as well as at its surface.

25. Freezing and Melting • Freezing point- the temperature at which the solid and liquid are in equilibrium at 1 atm pressure

26. Stop

27. Phase Diagrams • Phase diagrams- a graph of pressure versus temperature that shows the conditions under which the phases of a substance exist • Triple point- indicates the temperature and pressure conditions at which the solid, liquid, and vapor of the substance can coexist at equilibrium

28. Critical temperature- the temperature above which the substance cannot exist in the liquid state • Water 373.99°C • Critical pressure- the lowest pressure at which the substance can exist as a liquid at the critical temperature • Water 217.75 atm

30. At 6 atm, what is the boiling point of carbon dioxide?

31. Stop

32. Water • Water is the Earth’s most abundant liquid • Oceans, rivers, and lakes cover about 75% of the earth’s surface • 70-90% of the mass of living things is water

33. Structure of Water • The molecules in solid or liquid water are linked by hydrogen bonding • Ice consists of water molecules in a hexagonal arrangement. The empty spaces between molecules in this pattern accounts for the low density of ice • Once the molecule is heated, water molecules can crowd closer together • Thus, liquid water is denser than ice.

34. Physical Properties of Water • Pure liquid water is transparent, odorless, tasteless, and almost colorless • Any observable impurities are caused by dissolved minerals, liquids, or gases • It has a unique property of expanding in volume when it freezes • This explains why ice floats in water.

36. Molar heat of vaporization • It is a measure of the attraction between the particles of a liquid • Molar heat of fusion (H)- Depends on the attraction between the solid particles

37. Calculating Molar Heat q = m (H) q = heat (J) m = mass (g) Hvaporization H2O = 2260 J/g Hfusion H2O = 334 J/g

38. Practice Problems • How much heat energy is absorbed when 47.0 g of ice melts at STP? How much heat energy is absorbed when this same mass of liquid water boils? • What quantity of heat energy is released when 506 g of liquid water freezes? • What mass of steam is required to release 4.97 x 105 kJ of heat energy on condensation?