Chapter 7 States of Matter (gases, liquids and solids)

1. Chapter 7 States of Matter (gases, liquids and solids) • A solid has a definite shape and a definite volume • A liquid has no definite shape (it takes the shape of its container) • but a definite volume • A gas has no definite shape or volume solid liquid gas

2. In a gas, the particles are in constant random motion, each • particle being independent of the others present. • The particles in a liquid, though still close together, freely slide • over one another. • In a solid, the particles (atoms, molecules, or ions) are close • together and vibrate about fixed sites.

3. Kinetic Molecular Theory of Matter • Matter is composed of tiny particles (atoms, molecules, or ions) that have definite and characteristic sizes that do not change. • The particles are in constant random motion and therefore possess kinetic energy. • Kinetic energy – energy that matter possesses because of particle motion.

4. The particles interact with one another through attractions and repulsions and therefore possess potential energy. • Potential energy – stored energy that matter possesses as a result of its position, condition, and/or composition. • The kinetic energy (velocity) of the particles increases as the temperature is increased. • The particles in a system transfer energy to each other through elastic collisions.

5. Pages 165 - 166 Solid: High density Small compressibility Very small thermal expansion Liquid: High density Small compressibility Small thermal expansion Gas: Low density Large compressibility Moderate thermal expansion Fig. 7.5

6. I. Properties of gases A. Pressure P = force/area Usually measured by height of Hg (mercury) 1 atmosphere pressure = 1 atm = 760 mm Hg =760 torr

7. Figure 6.3

8. Page 178Chemical Connections Measure of blood pressure Systolic pressure Diastolic pressure

9. Systole is the contraction ofheart chambers, driving blood out of the chambers. Diastole is the period of time when the heart relaxes after contraction. Systolic pressure - the highest arterial pressure during each heart beat. Normal range: Diastolic pressure - the lowest arterial pressure between heart beats Normal range:

10. B. Volume, L C. Temperature, K 273K = 0oC K = oC + 273

11. D. The Gas Laws a) Boyle’s law Constant temperature or PV = constant or P1V1 = P2V2

12. b) Charles law Constant pressure or constant or

13. c) The Combined Gas Law Boyle's law: P1V1 = P2V2 Charles law: Combined gas law: or constant Combined gas law

14. Example (1) A gas occupies 3L at 2 atm. What would be the pressure if the volume was 6L at the same temperature? Example (2) A gas occupies 2.0 L at 200K and 1.0 atm pressure. What temperature would it be if the volume was 3.0L and the pressure was 380 torr?

15. d) The ideal Gas law (n = number of moles) Ideal gas law PV = nRT R = gas constant = 0.0821 Example 2.00 mol of CH4 occupies 16.4 L at 200K. What is the pressure?

16. g) Dalton's law of partial pressure Consider a mixture of two gases A and B at V, T. PV = nRT = PA + PB Total pressure partial pressure of A partial pressure of B Example: A 10 L container contains 2.0 mol O2 and 4.0 N2 at 300K. Find PO2, PN2 and PT.

17. In general Example: to a tank containing N2 at 2.5 atm and O2 at 1.5 atm we add an unknown quantity of CO2 until the total pressure in the tank is 5.2 atm. What is the partial pressure of CO2? http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::525::530::/sites/dl/free/0072828471/291136/movement_oxygen_carbon_dioxide.swf::Movement%20of%20Oxygen%20and%20Carbon%20Dioxide

18. E. Changes of state Figure 7.15 There are six changes of state possible for substances.

19. 1. Evaporation and condensation evaporation condensation H2O H2O

20. 2. Vapor pressure (v.p.) of liquids evaporation condensation rate (evaporation) = rate (condensation) liquid vapor H2O State of equilibrium (Saturation) Vapor pressure = partial pressure exerted by the vapor above the liquid at saturation at a given temperature

21. Figure 7.17 Evaporation of a Liquid in a Closed Container

22. Vapor pressure increases with temperature Vapor pressure Temperature

23. 3. Boiling – evaporation occurs anywhere in the liquid Normal boiling point – T at which v.p. of the liquid = 1 atm. or boiling T under 1 atm atm At 100oC, v.p. of water = 1 atm 1 atm v.p. (water) 100oC T

24. T 100oC Heating time

26. 4. Conditions that affect boiling point a) External Pressure: Boiling point increases as Pext increases b) Attractive forces between molecules: The stronger the attractive forces, the higher the boiling point

27. G. Intermolecular forces a) Dipole-dipole interaction d+d- d+d- H Cl H Cl H Cl H Cl H Cl H Cl Cl H Cl H Cl H Cl H

28. b) London dispersion forces Nonpolar molecules such as H2 can develop instantaneous dipoles and induced dipoles. The attractions between such dipoles, even though they are transitory, create London forces. Induced-induced dipole forces London force increases with size of the molecule

29. Consider

30. b) Hydrogen bonds H F H O H N Example: H2O figure 6.9 ball and stick models electron density models Structural formulas

31. H2O

32. If there were no hydrogen bonding between water molecules, the boiling point of water would be approximately - 80C. oC oC oC oC oC

33. cannot H-bond with another

34. In general For compounds of similar dipole moment, the larger the MW, the higher the boiling point. For compounds of similar MW, the larger the dipole moment, the higher the boiling point.

35. Boiling point of compounds that can form H-bonds are relatively high. H-bond > dipole-dipole forces > London forces

36. Circle those compounds below in which the molecules are capable of forming hydrogen bonds between themselves. NH3 NF3 HF CO2 In each pair below, circle the compound with the higher boiling point: (1) O2 or Cl2 (2) H2O or H2S (3) HBr or CF4