States of Matter Chapter 13

Chapter 13- The States of Matter  Gases- indefinite volume and shape, low density.  Liquids- definite volume, indefinite shape, and high density.  Solids- definite volume and shape, high density  Solids and liquids have high densities because their molecules are close together.

13.3 Liquids and Solids GasLiquidSolid Shape (e.g. fixed or not fixed) Volume (e.g. definite or indefinite) Density (relatively high, medium, or extremely low) Compressibility (e.g. relatively high, low, or extremely low) Fluidity (e.g. flows or does not flow) Not fixed Fixed IndefiniteDefinite Extremely low Medium Relatively high Relatively high Low Extremely low flows does not flowDiffusion (e.g. rapid, medium, or none) rapid mediumnone

Ideal Gas  Definition of a gas in ideal conditions.  It states: 1. Individual molecules have no mass. 2. Individual molecules have no volume. 3. No intermolecular force between molecules.

Elastic Collisions Elastic collisions are defined as a collision in which no energy is lost. H and S Balls

Inelastic Collisions Inelastic collisions lose energy as heat and sound during the collision. Most collisions are inelastic.

The Kinetic Theory of Gases Makes three descriptions of gas particles

1. A gas is composed of particles  molecules or atoms  Considered to be hard spheres far enough apart that we can ignore their volume.  Between the molecules is empty space. The Kinetic Theory of Gases Makes three descriptions of gas particles

2. The particles are in constant random motion.  Move in straight lines until they bounce off each other or the walls. 3. All collisions are perfectly elastic

Kinetic Energy and Temperature  Temperature is a measure of the Average kinetic energy of the molecules of a substance.  Higher temperature faster molecules.  At absolute zero (0 K) all molecular motion would stop.

Pressure  Pressure is the result of collisions of the molecules with the sides of a container.  A vacuum is completely empty space - it has no pressure.  Pressure is measured in units of atmospheres (atm).  It is measured with a device called a barometer.  Atmospheric Pressure Collisions of atoms and molecules in air with objects Collisions of atoms and molecules in air with objects

Standard Atmospheric Pressure  14.7 pounds per square inch.  760 mm Hg = 760 torrs  X 10 5 Pa = kPa  1 atm

Barometer  At one atmosphere pressure a column of mercury 760 mm high. Dish of Mercury Column of Mercury 1 atm Pressure

Barometer  At one atmosphere pressure a column of mercury 760 mm high.  A second unit of pressure is mm Hg  1 atm = 760 mm Hg  Third unit is the Pascal  1 atm = kPa 760 mm 1 atm Pressure

STP: Standard Temperature and Pressure Standard Temperature 0  C = 273 K Standard Temperature 0  C = 273 K

Kelvin Temperature Scale Kelvins =  Celsius + 273

Three Variables Describe a Gas  Average kinetic energy  temperature in kelvins.  Volume is measured in liters.  Pressure is the force of the gas particles.

Diffusion The process by which particles disperse from regions of higher concentration to regions of lower concentration

Crystals  A solid has a definite volume and a definite shape.  True solid substances are crystals.  Orderly repeating pattern called a crystal lattice  Examples: salt, sugar, bismuth, ice

Amorphous Solids  Solids with no crystal structure  Breaks into smaller pieces of varying shapes and sizes.  Examples: glass, wax and obsidian

Vapor Pressure and Boiling Point  Evaporated particles create pressure in a closed container.  Boiling point of a substance is the temperature at which its vapor pressure is equal to atmospheric pressure.  Normal boiling point of a liquid is the temperature at which its vapor pressure is equal to 1 atm

Same KE – different speed  Mass affects kinetic energy.  Less mass, less kinetic energy at the same speed  The smaller particles must have a greater speed to have the same kinetic energy.  Same temperature, smaller particles move faster