Chapter 16 States of Matter

Sec. 1: Kinetic Theory Kinetic Theory—an explanation of how particles in matter behave. There are 3 assumptions of kinetic theory: All matter is made of small particles These particles are in constant motion The particles collide with each other and the walls of their container.

Solid State The particles of a solid are closely packed together. Most solids have a specific geometric arrangement. You can tell the chemical and physical properties of a solid based on the type of arrangement that a solid forms. Solids have a definite shape and volume.

Liquid State Liquids form at a melting point—the temp. that a solid begins to liquefy. Particles in a liquid have more kinetic energy than in a solid—they are moving faster. These particles can slide past each other allowing liquids to flow and take the shape of their container. Liquids have a definite volume, but no definite shape.

Gas State Particles in a gas have more kinetic energy than in a liquid. A liquid becomes a gas through vaporization or evaporation. Gas particles have enough kinetic energy to overcome the attractions between them. Gases have no definite shape or volume. They can spread apart to fill the container they are in. Diffusion—the spreading out of particles throughout a volume until they are uniformly distributed.

States of Matter

Plasma State Plasma is the most common state of matter in the universe. Plasma—matter consisting of positive and negative particles at very high temperatures. When gases get very hot, the faster the particles move, and the greater the force is when they collide. This forces the electrons to be pulled off. All stars (including the sun) consist of plasma. Plasma is also found in lightning, neon light tubes, and auroras.

Expansion of Matter As the temperature of particles increases, the particles move faster and separate. The separation of particles causes the whole object to expand. Thermal Expansion—an increase in the size of a substance when temperature increases. Examples: Solid: Expansion joints in sidewalks Liquid: Thermometer Gas: Hot air balloon

Water: The Exception Water is an exception to thermal expansion because liquid water expands as it is cooled into a solid. Water molecules are unusual because they have highly positive areas and highly negative areas. As the molecules move closer, the unlike charges are attracted. This causes some empty spaces in the structure. The empty space in ice is larger than in liquid water.

Solid or Liquid? Some substances have unusual behavior. They have properties of both solids and liquids. Amorphous solids—solids that lack the ordered structure found in crystals. Examples: Glass and plastic Liquid Crystals—start to flow as they melt, but do not lose their ordered arrangement completely Examples: Liquid Crystal Displays (LCD) in watches, calculators, computers, and TVs.

Buoyancy http://www.youtube.com/watch?v=hkT3ulsGWyA&feature=PlayList&p=087CE258DB85E875&index=8

Sec. 2: Properties of Fluids Buoyancy—the ability of a fluid (liquid or gas) to exert an upward force on an object immersed in it. This is what causes ships to float. Archimedes’ Principle—the buoyant force on an object is equal to the weight of the fluid displaced by the object. An object will float if its density is less than the density of the fluid it is placed in.

Pascal’s Principle Pressure—force exerted per unit area Pressure = Force/Area P = F/A Pascal’s Principle—pressure applied to a fluid is transmitted throughout the fluid. Example: you squeeze 1 end of a toothpaste tube, toothpaste comes out the other end.

Bernoulli’s Principle Bernoulli’s principle describes how people were able to build a machine that can fly. Bernoulli’s Principle—as the velocity of a fluid increases, the pressure exerted by the fluid decreases. Airplane wings were designed to reduce pressure above the wings.

Fluid Flow Viscosity—a resistance to flow by a liquid. Example: Take syrup out of the fridge, pour it, and it flows slowly; heat it up, and it flows faster. Cold syrup has high viscosity; warm syrup has low viscosity. A rise in temp. increases the movement of particles in any substance.

Caltech: The Mechanical Universe - 45 - Temperature and Gas Laws

Sec 3: Behavior of Gases Boyle’s Law—when volume is decreased, pressure is increased (and vice versa) as long as temperature is constant. The equation for Boyle’s Law is P1V1 = P2V2 The subscript 1 represents initial pressure and volume, and the 2 represents final P & V. The unit for pressure is pascals & the unit for volume is liters.

The Pressure-Temperature Law As temperature increases, the pressure increases too (and vice versa) This is why you should keep pressurized spray canisters away from heat.

Charles’s Law Charles’s Law—the volume of a gas increases with increasing temperature (and vice versa) The equation for Charles’s Law is V1 = V2 T1 T2 Again, 1 is initial, and 2 is final.