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Chapter 10

Chapter 10. States of Matter. 10.1 Kinetic Molecular Theory (KMT). “Particles of Matter are always in motion” States of Matter We will discuss the KMT in terms of : 1. Gases 2. Liquids 3. Solids. KMT - Gases. Ideal gas- follows all of the tenets of the KMT.

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Chapter 10

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  1. Chapter 10 States of Matter

  2. 10.1 Kinetic Molecular Theory (KMT) “Particles of Matter are always in motion” States of Matter We will discuss the KMT in terms of : 1. Gases 2. Liquids 3. Solids

  3. KMT - Gases • Ideal gas- follows all of the tenets of the KMT. • 1. Gases consist of large numbers of atoms/molecules that are in continuous, random motion. • 2. The combined volume of all the atoms/molecules of the gas is negligible relative to the total volume in which the gas is contained.

  4. Gases Cont. • 3. Attractive and repulsive forces between gas particles is negligible. • 4. Energy can be transferred between particles during collisions, but the average kinetic energy of the particles does not change with time (assuming temperature is constant) = collisions are elastic • 5. The average kinetic energy of the particles is proportional to the absolute temperature. • K.E. = ½ mv2

  5. Properties of Gases • Expansion-gases occupy the volume of the container they are enclosed in. • Fluidity- gas particles move like liquids because there are no attractive or repulsive forces among them • Density- gases have low densities because of the large amounts of space between the particles.

  6. Properties of Gases Cont. • Compressibility- Gases can be easily condensed with an increase in pressure due to the large space between the particles. • Diffusion- the random mixing of particles due to their constant motion. • Effusion- gas particles pass through a tiny opening. • Rate is directly proportional to the velocities of the particles. (Smaller particles move faster and vice-versa)

  7. Real Gases • Those that do not conform to the 5 parts of the KMT. • When gases are held at high pressure and low temperatures they deviate from their expected behavior. • Noble gases conform the most to the KMT and act like ideal gases. • The more polar the gas molecule the more it deviates from the KMT and acts like a real gas.

  8. 10.2 Liquids • Have a definite volume and take the shape of its container • Particles are closer together so their attractive forces are stronger than in gases (think strength of intermolecular forces) • Fluid – the ability to flow and occupy the shape of its container.

  9. Liquids Cont. • Density – fairly high considering the closer arrangement of the particles • Incompressibility- because of the close proximity to one another, the particles in a liquid can’t be pushed much closer together. • Diffusion- liquids move easily among other liquids. Attractive forces and temperature of the particles lends to a slower diffusion rate of the liquid particles.

  10. Liquids Cont. • Surface Tension- a force that attracts adjacent particles on a liquids’ surface together enough to decrease the surface area. • The higher the intermolecular forces the higher the surface tension. • Water has a fairly high surface tension.

  11. Liquids Cont. • Capillary Action – the attraction of the surface of a liquid to the surface of a solid. • Meniscus • Chromatography • Phloem tubes in plants

  12. Liquids Cont. • Vaporization – liquid changing to a gas • Evaporation – vaporization at the surface of a liquid • Individual particles gain enough kinetic energy to break the I.F. and escape as a gas. • Freezing – liquid changing to a solid • Due to the increased intermolecular attractions among the particles

  13. 10.3 Solids • Highly ordered arrangement with minimal movement among the particles • I.F. exert stronger forces due to this proximity • Types: • Crystalline- geometric, repeating pattern of particles • Amorphous- random arrangement of particles • Glass, obsidian • “without shape”

  14. Solids Cont. • Melting- changing a solid to a liquid by applying heat energy • Overcome I.F. and break apart from the crystalline structure • Supercooled liquids (amorphous solids) – retain some liquid properties due to their lack of a uniform, organized pattern • High Density • Low diffusion rate

  15. Solids Cont. • Types of Crystals (p. 340) • 1. Ionic - NaCl • 2. Covalent Network – SiO2 • 3. Metallic - Cu • 4. Covalent Molecular – NH3

  16. Changes of State • Phase – when a substance has uniform composition and properties • Melting, freezing, vaporization, condensation, sublimation, deposition • Equilibrium – when two phases occur at the same rate. E.g., melting freezing

  17. Changes of State Cont. • Equilibrium Vapor Pressure – the pressure exerted by a vapor in equilibrium with its liquid at a given temp. • Proportional to the concentration of molecules in the vapor phase. • Increases with an increase in temperature • Volatile liquids (those that evaporate easily) have higher V.P. because they tend to have weaker I.F. between the molecules. • Vapor Pressure Animation

  18. Changes of State Cont. • Boiling – change of a liquid to vapor at the surface and within the liquid. • Boiling point – when the V.P. equals the atmospheric pressure. • Normal B.P. of water = 100oC, (normal atmospheric pressure of 1 atm, 760 torr, 101.3 kPa) • B.P. Animation

  19. Vapor Pressures of Various Substances

  20. Identity of Substances • A – Diethyl ether • B – Benzene • C - water

  21. Phase Diagrams • Phase Diagram Explanation

  22. Phase Diagram for Water

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