unit 9 - states of matter and gas behavior chemistry chapters 12-13

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Slide 2 Unit 9 - States of Matter and Gas Behavior Chemistry Chapters 12-13 Slide 3 The Behavior of Gases Kinetic-molecular theory explains the different properties of solids, liquids, and gases. Atomic composition affects physical and chemical properties. The kinetic-molecular theory describes the behavior of matter in terms of particles in motion. Gases expand, diffuse, exert pressure, and can be compressed because they are in a low density state consisting of tiny, constantly- moving particles. Slide 4 The Behavior of Gases Gases consist of small particles separated by empty space. Gas particles are too far apart to experience significant attractive or repulsive forces. Gas particles are in constant random motion. An elastic collision is one in which no kinetic energy is lost.elastic collision Kinetic energy of particles is directly proportional to temperature Gases consist of small particles separated by empty space. Gas particles are too far apart to experience significant attractive or repulsive forces. Gas particles are in constant random motion. An elastic collision is one in which no kinetic energy is lost.elastic collision Kinetic energy of particles is directly proportional to temperature Slide 5 Kinetic energy of a particle depends on mass and velocity. Temperature is a measure of the average kinetic energy of the particles in a sample of matter. Temperature Kinetic energy of a particle depends on mass and velocity. Temperature is a measure of the average kinetic energy of the particles in a sample of matter. Temperature The Behavior of Gases Slide 6 Great amounts of space exist between gas particles. Compression reduces the empty spaces between particles. Great amounts of space exist between gas particles. Compression reduces the empty spaces between particles. Slide 7 Gas Pressure Pressure is defined as force per unit area. Pressure Gas particles exert pressure when they collide with the walls of their container. The particles in the earths atmosphere exert pressure in all directions called air pressure. There is less air pressure at high altitudes because there are fewer particles present, since the force of gravity is less. Pressure is defined as force per unit area. Pressure Gas particles exert pressure when they collide with the walls of their container. The particles in the earths atmosphere exert pressure in all directions called air pressure. There is less air pressure at high altitudes because there are fewer particles present, since the force of gravity is less. Slide 8 Gas Pressure Barometers are instruments used to measure atmospheric air pressure. Barometers Barometers are instruments used to measure atmospheric air pressure. Barometers Slide 9 Gas Pressure The average height of a mercury column in a barometer at sea level is 760 mm (760 mmHg) There are other units of pressure as well with the following relationships: 1.00 atm = 760 mmHg = 760 torr = 101.3 kPa The average height of a mercury column in a barometer at sea level is 760 mm (760 mmHg) There are other units of pressure as well with the following relationships: 1.00 atm = 760 mmHg = 760 torr = 101.3 kPa Slide 10 Gas Pressure Daltons law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases of the mixture. Daltons law of partial pressures The partial pressure of a gas depends on the number of moles, size of the container, and temperature and is independent of the type of gas. Daltons law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases of the mixture. Daltons law of partial pressures The partial pressure of a gas depends on the number of moles, size of the container, and temperature and is independent of the type of gas. Slide 11 Gas Pressure P total = P1 + P2 + P3 +Pn Partial pressure can be used to calculate the amount of gas produced in a chemical reaction. P total = P1 + P2 + P3 +Pn Partial pressure can be used to calculate the amount of gas produced in a chemical reaction. Slide 12 Gas Pressure Gases are often collected by water displacement, but water vapor is introduced to the gas sample (mixture of gases) You can use Daltons law to get the partial pressure of the gas without the water vapor Gases are often collected by water displacement, but water vapor is introduced to the gas sample (mixture of gases) You can use Daltons law to get the partial pressure of the gas without the water vapor Slide 13 Forces of Attraction Attractive forces between molecules cause some materials to be solids, some to be liquids, and some to be gases at the same temperature. Intermolecular forcesincluding dispersion forces, dipole-dipole forces, and hydrogen bondsdetermine a substances state at a given temperature. Slide 14 Forces of Attraction Prefix INTRA means within, where INTER means between Slide 15 Forces of Attraction Dispersion forces are weak forces that result from temporary shifts in the density of electrons in electron clouds. Weakest of all intermolecular forces Dispersion forces become increasingly stronger as molecule gets more electrons, which explains why iodine is a solid but fluorine is a gas at room temperature Dispersion forces are weak forces that result from temporary shifts in the density of electrons in electron clouds. Weakest of all intermolecular forces Dispersion forces become increasingly stronger as molecule gets more electrons, which explains why iodine is a solid but fluorine is a gas at room temperature Slide 16 Forces of Attraction Dipole-dipole forces are attractions between oppositely charged regions of polar molecules. Dipole-dipole forces Dipole-dipole forces are attractions between oppositely charged regions of polar molecules. Dipole-dipole forces Slide 17 Forces of Attraction Hydrogen bonds are special dipole-dipole attractions that occur between molecules that contain a hydrogen atom bonded to a small, highly electronegative atom with at least one lone pair of electrons, typically fluorine, oxygen, or nitrogen. Hydrogen bonds Hydrogen bonds are special dipole-dipole attractions that occur between molecules that contain a hydrogen atom bonded to a small, highly electronegative atom with at least one lone pair of electrons, typically fluorine, oxygen, or nitrogen. Hydrogen bonds Slide 18 Forces of Attraction Slide 19 Liquids and Solids Liquids and solids are called condensed phases because their particles are very close together and do not have the energy necessary to escape the sampletheir motion is limited The particles in solids and liquids have a limited range of motion and are not easily compressed. Slide 20 Liquids and Solids Solid particles are arranged in a crystal arrangement where they are fixed in position. This arrangement results in a substance that has a defined shape and volume. Solid particles are arranged in a crystal arrangement where they are fixed in position. This arrangement results in a substance that has a defined shape and volume. Slide 21 Liquids and Solids Liquid particles have enough energy to slide by other particles, but do not have the energy to escape the sample itself. This results in a substance that has a fixed volume but takes the shape of its container. Liquid particles have enough energy to slide by other particles, but do not have the energy to escape the sample itself. This results in a substance that has a fixed volume but takes the shape of its container. Slide 22 Phase Changes Heat is the transfer of energy from an object at a higher temperature to an object at a lower temperature. Matter changes phase when energy is added or removed. Slide 23 Phase Changes When ice is heated, the ice eventually absorbs enough energy to break the hydrogen bonds that hold the water molecules together. When the hydrogen bonds break, the particles move apart and ice melts into water. The melting point of a crystalline solid is the temperature at which the forces holding the crystal lattice together are broken and it becomes a liquid.melting point When ice is heated, the ice eventually absorbs enough energy to break the hydrogen bonds that hold the water molecules together. When the hydrogen bonds break, the particles move apart and ice melts into water. The melting point of a crystalline solid is the temperature at which the forces holding the crystal lattice together are broken and it becomes a liquid.melting point Slide 24 Phase Changes Vaporization is the process by which a liquid changes to a gas or vapor. Vaporization Evaporation is vaporization only at the surface of a liquid. Evaporation Vaporization is the process by which a liquid changes to a gas or vapor. Vaporization Evaporation is vaporization only at the surface of a liquid. Evaporation Slide 25 Phase Changes In a closed container, the pressure exerted by a vapor over a liquid is called vapor pressure.vapor pressure In a closed container, the pressure exerted by a vapor over a liquid is called vapor pressure.vapor pressure Slide 26 Phase Changes The boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure.boiling point The boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure.boiling point Slide 27 Phase Changes Evaporation vs Boiling Summary: Evaporation is the result of surface level molecules obtaining enough energy to escape the sample as a gas Boiling occurs throughout the sample when the vapor pressure of the liquid is the same as the atmospheric pressure Evaporation vs Boiling Summary: Evaporation is the result of surface level molecules obtaining enough energy to escape the sample as a gas Boiling occurs throughout the sample when the vapor pressure of the liquid is the same as the atmospheric pressure Slide 28 Phase Changes Sublimation is the process by which a solid changes into a gas without beco