Chapter 16--Solids, Liquids and Gases

Section 1—Kinetic Theory

• Kinetic Theory—an explanation of how particles in matter behave

1. All matter is composed of small particles

2. Particles are in constant random motion

3. Particles are colliding w/ea other and the walls of their container

Particles lose some energy during collisions/but amt is very small

Thermal energy

• Thermal energy is the total amt of a material’s particles including kinetic and potential energy

• When temp is lowered, particles will have less thermal energy and vibrate more slowly

Average Kinetic Energy

• Temperature means the average kinetic energy in the substance OR how fast particles are moving– Book examples—pg. 489

SOLID STATE:

Solids—contain particles that are closely packed together

-have a specific shape/arrangement

*particles don’t slide past each other

Liquid State:

• Liquids: have more kinetic energy than solids/particles slip by ea/other—flow

-Have definite volume

Melting point—temp at which a solid begins to liquefy

Heat of fusion—amt of energy needed to change from solid to liquid phase

Gas State:

• Gases: take the shape of their container/no fixed volume or shape

• Vaporization occurs by: evaporation and boiling

• Boiling Point: the temperature at which pressure of the vapor in the liquid equals outside pressure

• Heat of vaporization: amt of energy required for a liquid to change to a gas

Plasma State:

• Diffusion—spreading of particles throughout a given volume until uniformly distributed– Occurs most rapidly in gases

Plasma—matter consisting of positively and negatively charged particles w/neutral charge

ex: sun, stars, lightning bolts, auroras

Thermal Expansion

• Thermal expansion—an increase in size of a substance when the temp is increased

• Expansion in Liquids/Gases– Ex: thermometer/hot air balloons– Typically gases expand most with

heat, then liquids,then

solids

• Evaporation: changing from liquid to a gas (as a liquid is heated)

• Condensation: when water vapor in air cools and returns to liquid state

• Sublimation: when liquids change from the solid state to the gaseous state (skips melting)

Strange Behavior of Water

• Water molecules have highly positive and highly negative areas

• These charged regions affect the behavior of water

• As temp drops/particles move closer together

• Empty spaces form in ice and are larger than in liquid water

• So: water expands when going from liquid to solid state

Amorphous Solids and Liquid Crystals

• Amorphous solids—do not have a definite temp at which they change from solid to liquid, but change gradually over a temp range– Ex: plastics and glassLiquid crystals:

start to flow during the melting phase similar to a liquid, but do not lose their ordered arrangement completely

ex: LCD-watches, calc’s, etc.

SECTION 2: Properties of Fluids

• Buoyancy: the ability of a fluid to exert an upward force on an object immersed in it

• IF buoyant force = object’s weight, then object FLOATS

• IF buoyant force < object’s weight, object will SINK

Archimedes’ Principle

• Archimedes found that the buoyant force on an object = weight of fluid displaced by object

• Ex: pg. 497/498

• Density = mass / volume

• An object will float if its density is less than the density of the fluid it is placed in

Pascal’s Principle

• Pressure = force /area

• Pascal’s Principle: pressure applied to a fluid is transmitted throughout the fluid

• Ex: hydraulic machines—raising cars on hydraulics

Bernoulli’s Principle

• Bernoulli’s Principle:-as the velocity of a fluid increases, the pressure exerted by the fluid decreases

**paper ex: pg. 500Fluid Flow:Viscosity—a resistance to flow by a

fluid-fluids vary in their tendency to flow because their structures differ

SECTION 3: Behavior of Gases

• Pressure:– = force / area– Is measured in Pascals

Particle collisions create pressure and keep objects inflated by pushing the walls of the container outward

The more collisions, the more the walls of the container will expand and pressure increases

ex: balloons

VISCOSITY

• When you heat a liquid, the viscosity of the liquid DECREASES

• When you cool a liquid, the viscosity of the liquid INCREASES

• (think syrup in the fridge, vs. syrup in the microwave)

Boyle’s Law

• Boyle’s Law:– If you decrease the volume of a

container of gas and hold the temp constant, the pressure of the gas will increase

– An increase in the volume of the container causes the pressure to drop, if the temp remains constant

• ex: rubber /neoprene weather balloons—pg. 504

Pressure-Temperature Law

• If the pressure becomes greater than the canister can hold, it will explode

• CHARLES”S LAW:

the volume of a gas increases with increasing temperature as long as pressure does not change

As with Boyle’s law, the reverse is true also.