States of Matter

The nature of gases, liquids & solids is all about the motion of

the particles.

Solid Liquid Gas

Movement of particles

Rotate & vibrate

Have “flow”-can move past one another

Have “flow.” In constant, random motion.

Organization of Particles

Packed in a crystal arrangement

Not organized Not organized

Compressible? No No-particles in contact w/one another

Yes. Much empty space btwn particles

Definite Volume?

Yes Yes No-Take on size of container

Definite Shape?

Yes No-take on shape of container

No-Take on shape of container

Solids

• Movement of Particles in a Solid

• Particles packed in a regular repeating pattern-”crystal”– see p 397-398– Crystal structure

• Some elements have more than 1 crystal arrangement-”allotropes”- : carbon

Allotropes of Carbon

• Diamond

• Graphite

• Comparing Diamond & Graphite

Another Allotrope of Carbon: Buckminsterfullerine: C60

Solids, cont.

• Solids at room temp tend to be metal elements & ionic compounds. Have high melting points. – Ex: copper, salts

• Also some molecular compounds are solids. They have low melting points.– ex: living things, sugar, .

Non-Crystalline Solids

• Solids that don’t have a crystal structure

• Amorphous Solid-Lacks ordered internal structure: rubber, plastic, asphalt

• Glass- Transparent inorganic substances cooled w/o crystallizing– Arrangement of particles midway btwn that of

a crystalline solid & a liquid– Breakage of glasses & crystalline solids

differs

Gases & Kinetic Theory

1. Gas particles are molecules or atoms but a gas is mostly empty space.

2. Gas particles move in constant random motion.

3. Particles continue in a straight line until acted on by a force.

4. All collisions are perfectly elastic (no energy is lost or gained.)

Gas Pressure

•Gas pressure is the result of collisions of gas particles on an object

Gas Pressure

VacuumA lack of gas particles (no particles = no gas pressure)

Atmospheric pressure

•results from the collision of air molecules with objects

•Measured with a barometer

Barometer• Height of Hg in

tube depends on pressure exerted by particles of air colliding with Hg in dish

• Affected by weather & altitude

Atmospheric Pressure

•Air density decreases with increased altitude. Why?

•Less particles higher up, therefore less pressure.

As Altitude increases - air pressure decreases

•On top of mountains - the air is thin (few particles)

Units for Measuring Atmospheric Pressure

•SI unit of measurement is the Pa (Pascal)

•Normal atmospheric pressure ~100,00 Pa

• 1atm =

• 760 mm Hg =

• 101.3 kPa =

• 14.7 psi

Plasma-the 4th form of matter

• Most common form of matter in universe

• Least common form of matter on Earth

• ionized gas

• occur @ very high temperature

• Electrons are stripped away

• Ex: fluorescent lights, lightning, stars

Kinetic Theory

• Particles of a substance are in constant random motion.

• Their energy is called __________energy!

Measuring Temperature

• Kelvin Scale is the best measure of kinetic energy

• Absolute zero is when particles stop moving. (This temp has never been reached.)

• Tk = (Tc + 273)K

• Tc = (Tk-273) C

The Kelvin Scale

• The units in the Fahrenheit & Celsius scales are degrees.

• The units in the Kelvin scale are kelvins.

Kinetic energy of a particle

• Depends on 2 things– Its mass– Its speed

– See Figure 10.15 (p 351 of text)– Compare the 1st 2 containers

• H2 at 300K O2 @ 300K

• Which has greater kinetic energy?• Which is moving faster?

Intermolecular Forces/Attractions

• hold particles close together

• reduce the space between the particles

• These 2 facts determine the physical properties of the liquids

Diffusion

• Def: the process by which particles of matter fill a space b/c of random motion

• Particles move from an area of greater to lesser concentration.

• Ex: perfume sprayed in a room

• Ex: dye in a container of water.

Diffusion-Why does it happen?

• Molecules are bumping around randomly.

• If you spray perfume, for example, the particles of air will bump into the perfume particles until they are spread around evenly.

Kinetic Energy & Temperature

• When we measure temperature we are measuring the movement of molecules/atoms.

• Temperature measures the average kinetic energy of the particles.

• at 0 K ( absolute zero) - there is no movement

Kinetic Energy & Change in State

• How does temperature relate to particle motion?

• Faster = more energy

• More energy= higher temperature

• Temperature is actually a measure of the AVERAGE kinetic energy of the particles.

Changes of State

• Evaporation & Condensation(liquid=> gas) (gas=> liquid)

Melting & Solidification(solid=>liquid) (Liquid=>solid)

SublimationSolid=> gas

Changes of State

The Relationship Between Melting & Freezing Point• Melting Point of Water is___• Freezing Point of Water is ___• Therefore, MP ___ FP

The Relationship Between Boiling & Condensation Point• Boiling point (Evaporation pt) of water is ___• Condensation point of water is ___• Therefore, BP ___ CP

Changes of State

• Temperature plays an important role!

• Evaporation-point at which particles of liquid have enough energy to escape the surface of the liquid.

• Things that affect the rate of evaporation– Surface area– Temperature– humidity

Vapor Pressure & Evaporation

• Vapor Pressure is the pressure of the gas of a substance in equilibrium with its liquid.

• HUH?

• VAPOR PRESSURE

Vapor Pressure of Different Substances

• Ethyl (Rubbing) alcohol• Water

• Which one evaporates more easily?• Which one is harder to keep from evaporating

(needs more vapor molecules above it pushing down)?

• So, which has more molecules in vapor form?• More vapor molecules = more vapor pressure?

Phase Changes

Notice What happens to the temperature when

1. ice begins to melt and

2. water begins to boil

Water: Solid-Liquid-Gas

Heat of Vaporization

• You notice that the temperature ________ for a period of time when the boiling point is reached.

• The energy that is being added is being used to break bonds, not speed up particles (no increase in kinetic energy!)

• Therefore no increase in temperature until all bonds are broken.

• The amount of energy necessary to break the bonds is called “Heat of Vaporization”

• Each substance has a different H.O.V.

Change in Energy w/o Change in Temperature?

• http://id.mind.net/~zona/mstm/physics/mechanics/energy/heatAndTemperature/changesOfPhase/changeOfState.html

• Animated motion of particles in ice & liquid water

Heat of Fusion

• When water freezes into ice, its temp also stays the same for a while.

• During this time, there is energy released while bonds are formed.

• Therefore, no energy is lost by the particles (no decrease in kinetic energy.)

• This amount of energy released is called Heat of Fusion.