Chapter 3Chapter 3

The Four Phases

Phase Changes

Boyle’s Law & Charles’s Law

Matter exists in four phases:

• SOLID

• LIQUID

• GAS

• PLASMA

Phases of Matter

SOLIDSSOLIDS• Have a definite shape• Have a definite volume• Particles packed very closely together – they

are sometimes arranged in a regular repeating pattern called a CRYSTAL

• Particles may only vibrate – too close to move• Some particles are NOT arranged in a pattern –

called AMORPHOUS solids – and may lose their shape over time under certain conditions

• Examples include: window glass, candle wax, tar, silicone rubber

LIQUIDSLIQUIDS• Have no definite shape – particles are free to

move or flow because they are not as closely packed

• Have a definite volume – but must take the shape of its container

• Some liquids flow more freely than others

• VISCOSITY is a liquid’s resistance to flow

• Which is more viscous – HONEY or WATER?

• Oil & other lubricants have high viscosity

GASESGASES• No definite shape• No definite volume• Particles are free to move so they fill the

available space, regardless of the size or shape of the container

• What holds Earth’s atmospheric gases so they don’t expand into deep space?

• Particles are in constant motion – moving so fast that they’re colliding with each other & the container at great speeds

PLASMAPLASMA

• Rarely found on Earth

• Very common in the universe (stars, like our sun)

• Matter is extremely high in energy

• Very dangerous to living things

BEHAVIOR of GASESBEHAVIOR of GASES• Because the particles of a gas are in

constant motion, changing the temperature of or the pressure on the particles will have an effect on the behavior of the particles in the space (volume) they occupy

• Two laws help us understand the relationship

Boyle’s LawBoyle’s Law• With a fixed amount of gas:

– when the pressure increases, the volume decreases

– when the pressure decreases, the volume increases

• This is an inverse proportion

P1 = V2

P2 V1

Charles’s LawCharles’s Law• With a fixed amount of gas:

– when the temperature increases, the volume increases

– when the temperature decreases, the volume decreases

• This is a direct proportion

T1 = V1

T2 V2

Which law is being shown in this cartoon?

PHASE CHANGESPHASE CHANGES• Substances will change from one phase to

another by adding (absorbing) or taking away (releasing) ENERGY

• Adding energy causes the particles in a substance to move faster & spread out

• Releasing energy causes the particles in a substance to slow down & come together

• Example = water vapor, liquid water, & ice

Phases changes are beneficial:

•This is why freezing water can “save” fruit by the release of energy which the fruit takes on

•This is also why evaporation of water or sweat from the skin is a cooling process

Phases changes include:

•MELTING – change from a solid to a liquid

•FREEZING – change from a liquid to a solid

•VAPORIZATION – change from a liquid to a gas (like evaporation)

•CONDENSATION – change from a gas to a liquid

Phase Changes

Sublimation

•Some substances are able to change from a solid state directly to a gaseous state without ever becoming a liquid

Examples include:

dry ice, fallen snow, air freshener

Melting Point vs. Freezing PointMelting Point vs. Freezing Point

• The temperature at which a solid changes to a liquid

• The temperature at which a liquid changes to a solid

• They’re equal to each other, meaning water will melt & freeze at 0°C

What is happening at X?What is the temperature?

Evaporation vs. BoilingEvaporation vs. Boiling• Evaporation occurs when a phase

change (liquid to gas) occurs from the surface of the liquid

• Boiling causes the phase change to occur within the liquid & gas bubbles rise to the top

Condensation vs. Boiling PointCondensation vs. Boiling Point

• The temperature at which a gas changes to a liquid

• The temperature at which a liquid changes to a gas

• They’re equal to each other, meaning water will condense & boil at 100°C

Phase Change Graph for Water