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:1. All matter is made of small particles

2. These particles are in constant motion

3. The particles collide with each other and the walls of their container.

Solid StateThe 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 FlowViscosity—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 LawAs temperature increases,

the pressure increases too (and vice versa)

This is why you should keep pressurized spray canisters away from heat.

Charles’s LawCharles’s Law—the volume of a

gas increases with increasing temperature (and vice versa)

The equation for Charles’s Law isV1 = V2

T1 T2

Again, 1 is initial, and 2 is final.