States of Matter

1. States of Matter Ch.13 Section 1: The Nature of Gases Section 2: The Nature of Liquids Section 3: The Nature of Solids Section 4: Changes of State

2. Section 13.1 What does the word Kinetic Refer to? Kinetic energy – the energy an object has because of its motion.

3. Kinetic Theory • According to the kinetic theory, all matter consists of tiny particles that are in constant motion. PhET Simulation for States of Matter Basics

4. Kinetic Theory and a Model for Gases The particles in a gas are considered to be small, hard spheres with an insignificant volume. The motion of particles in a gas is rapid, constant, and random. All collisions between particles in a gas are perfectly elastic.

5. The particles in a gas are considered to be small, hard spheres with an insignificant volume. • Within a gas, the particles are relatively far apart compared with the distance between particles in a liquid or solid. • Between the particles, there is empty space. • No attractive or repulsive forces exist between the particles.

6. Bromine molecule The motion of particles in a gas is rapid, constant, and random. • Gases fill their containers regardless of the shape and volume of the containers. • An uncontained gas can spread out into space without limit.

7. The motion of particles in a gas is rapid, constant, and random. • The rapid, constant motion of particles in a gas causes them to collide with one another and with the walls of their container.

8. The motion of particles in a gas is rapid, constant, and random. • The particles travel in straight-line paths until they collide with another particle. • The particles change direction only when they rebound from collisions.

9. All collisions between particles in a gas are perfectly elastic. • During an elastic collision, kinetic energy is transferred without loss from one particle to another. • The total kinetic energy remains constant. Review Key Concepts again with simulation. PhET Simulation for States of Matter Basics

10. Describe an elastic collision between gas molecules. An elastic collision is one in which kinetic energy is transferred from one particle to another with no overall loss of kinetic energy.

11. How does kinetic theory explain gas pressure? Gas pressureresults from the force exerted by a gas per unit surface area of an object. Gas pressure is the result of billions of rapidly moving particles in a gas simultaneously colliding with an object. • An empty space with no particles and no pressure is called a vacuum.

12. Air Pressure • Air exerts pressure on Earth because gravity holds the particles in air within Earth’s atmosphere. • The collisions of atoms and molecules in air with objects results in atmospheric pressure. • Atmospheric pressure decreases as you climb a mountain because the density of Earth’s atmosphere decreases as the elevation increases.

14. Gas Pressure A barometeris a device that is used to measure atmospheric pressure. • At sea level, air exerts enough pressure to support a 760-mm column of mercury. • On top of Mount Everest, at 9000 m, the air exerts only enough pressure to support a 253-mm column of mercury.

15. When weather forecasters state that a low-pressure system is moving into your region, it usually means that a storm is coming. What do you think happens to the column of mercury in a barometer as a storm approaches? Why?

16. The SI unit of pressure is the pascal (Pa). • One standard atmosphere (atm)is the pressure required to support 760 mm of mercury in a mercury barometer at 25°C. • The numerical relationship among the three units is • 1 atm = 760 mm Hg = 101.3 kPa. • Recall that standard temperature and pressure (STP) are defined as a temperature of 0°C and a pressure of 101.3 kPa, or 1 atm.

17. SampleProblem 13.1 Converting between units of pressure A pressure gauge records a pressure of 450 kPa. Convert this measurement to a. atmospheres b. millimeters of mercury Conversion factor: 1 atm = 760 mm Hg = 101.3 kPa.

18. Converting between units of pressureAdditional Problems • What pressure, in kilopascals and in atmospheres does a gas exert at 385 mm Hg?

19. Converting between units of pressureAdditional Problems • The pressure at the top of Mount Everest is 33.7 kPa. Is that pressure greater or less than 0.25 atm?

20. Converting between units of pressureAdditional Problems • What pressure, in mm Hg and atm, does a sample of neon gas exert at 75.0 kPa?

21. Converting between units of pressureAdditional Problems • What pressure, in mm Hg and kPa, does a sample of argon gas exert at 1.561 atm?

22. What is the pressure in millimeters of mercury inside a vacuum? 0 mm Hg

23. Kinetic Energy & Temperature As a substance is heated, its particles absorb energy, some of which is stored within the particles. • This stored portion of the energy, or potential energy, does not raise the temperature of the substance. • The remaining absorbed energy does speed up the particles, that is, increases their kinetic energy. • This increase in kinetic energy results in an increase in temperature.

24. As a substance is heated, the particles tend to move faster, and their average kinetic energy increases. • As a substance cools, the particles tend to move more slowly, and their average kinetic energy decreases. • Notice that the molecules at the higher temperature have a wider range of kinetic energies.

25. Which point on each curve represents the average kinetic energy? Compare the shapes of the curves for cold H2O and hot H2O. What would happen to the shape of the curve if the water temperature were even higher? Even lower?

26. Kinetic Energy & Temperature • Absolute zero (0 K, or –273.15oC) is the temperature at which the motion of particles theoretically ceases. • STOP for Absolute Zero: PBS Nova film

27. Were you paying attention? 1. According to the kinetic theory, the particles in a gas • are attracted to each other. • are in constant random motion. • have the same kinetic energy. • have a significant volume.

28. Were you paying attention? 2. The pressure a gas exerts on another object is caused by • the physical size of the gas particles. • collisions between gas particles and the object. • collisions between gas particles. • the chemical composition of the gas.

29. Were you paying attention? 3. The average kinetic energy of the particles in a substance is directly proportional to the • Fahrenheit temperature. • Kelvin temperature. • molar mass of the substance. • Celsius temperature.

30. Were you paying attention? 4. What is the results of increasing the temperature of a gas sample? • Adecrease in the average kinetic energy of the sample • No effect on the sample • An increase in the average kinetic energy of the sample • Theparticles slow down.

31. The Kinetic Molecular Theory Postulates • Gases particles are in a state of constant, random motion. • Gas particles travel in a straight line until they collide with another particle or the walls of the container. • Gas particles are compressible • volume is negligible. • no force of attraction or repulsion between gas particles • Energy is conserved during collisions

32. Bell Ringer • When brewing coffee, identify the solvent and the solute. • What factors may affect coffee brewing results? • The ratio of water-to-coffee • Particle size of the coffee beans • The temperature of the water • The amount of time water and coffee are in contact with each other • Why is coffee brewed with hot water? • Water is a better solvent at hot, or near-boiling temperatures.

33. DATE: 9/30/2014 Bell Ringer • Compare and contrast; what is the difference between evaporation and boiling?

34. Section 13.2 A Model for Liquids Substances that can flow are referred to as fluids. • The ability of gases and liquids to flow allows them to conform to the shape of their containers.

35. Indefinite shape; flows • Fixed volume • Almost incompressible • Indefinite shape; flows • Indefinite volume; takes the shape of its container • Easily compressed • Why are liquids not as easily compressible and gases are? • According to kinetic theory, there are no attractions between the particles in a gas. • The particles in a liquid are attracted to each other. • - These intermolecular attractions keep the particles in a liquid close together

36. Indefinite shape; flows • Fixed volume • Almost incompressible • Indefinite shape; flows • Indefinite volume; takes the shape of its container • Easily compressed • Liquids are much more dense than gases. Floats = less dense Sinks = more dense

37. Evaporation • The conversion of a liquid to a gas or vapor (heat must be added)is called vaporization. • When this conversion occurs at the surface of a liquid that is not boiling (no heat applied), the process is called evaporation. • In a closed system, the molecules collect as a vapor above the liquid. Some condense back into a liquid. • In an open system, molecules that evaporate can escape from the system.

38. During evaporation, only those molecules with a certain minimum kinetic energy can escape from the surface of the liquid. Evaporation • As evaporation occurs, the particles with the highest kinetic energy tend to escape first. • Even some of the particles that do escape collide with molecules in the air and rebound back into the liquid.

39. Evaporation • A liquid evaporates faster when heated. • Heating the liquid increases the average kinetic energy of its particles. • The added energy enables more particles to overcome the attractive forces keeping them in the liquid state. • Evaporation is a cooling process

40. Vapor Pressure The evaporation of a liquid in a closed system differs from evaporation in an open system. • When a partially filled container of liquid is sealed, some of the particles at the surface of the liquid vaporize. • These particles collide with the walls of the sealed container, producing pressure. • A measure of the force exerted by a gas above a liquid is called vapor pressure.

41. Liquid Vapor (gas) condensation evaporation Vapor Pressure Over time, the number of particles entering the vapor increases and some of the particles condense and return to the liquid state. • Eventually, the number of particles condensing will equal the number of particles vaporizing.

43. Vapor Pressure In a system at constant vapor pressure, a dynamic equilibrium exists between the vapor and the liquid. The system is in equilibrium because the rate of evaporation of liquid equals the rate of condensation of vapor.

44. Vapor Pressure An increase in the temperature of a contained liquid increases the vapor pressure. Vapor Pressure and Temperature Change • This happens because the particles in the warmed liquid have increased kinetic energy. • More of the particles will reach the minimum kinetic energy necessary to escape the surface of the liquid.

45. Vapor Pressure Vapor Pressure and Temperature Change

46. Vapor Pressure Vapor Pressure and Temperature Change The vapor pressure data indicates how volatile a given liquid is, or how easily it evaporates.

47. 12.2 mm Hg or 1.63 kPa 43.9 mm Hg or 5.85 kPa Mercury Mercury Mercury Air Ethanol Ethanol Air at standard temperature and pressure Ethanol at 0°C Ethanol at room temperature (20°C) Vapor Pressure The vapor pressure is equal to the difference in height of the mercury in the two arms of the U-tube. The vapor pressure of a liquid can be determined with a device called a manometer. Vapor Pressure Measurements

48. Were you paying attention? In a sealed gas-liquid system at a constant temperature, eventually • there will be no more evaporation. • the rate of condensation decreases to zero. • the rate of condensation exceeds the rate of evaporation. • the rate of evaporation equals the rate of condensation.

49. Teacher Demo Vapor Pressure • Water vs. rubbing alcohol • Observe & infer which liquid has the greater vapor pressure at room temperature and explain their reasoning.

50. Boiling Point When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil. • Bubbles of vapor form throughout the liquid, rise to the surface, and escape into the air. • The boilingpoint(bp) is the temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid.