2/09 p. 22 Phase Changes Notes

• IQ: On your foldable on p. 21 write 2 examples each for solids, liquids, and gases on/by the respective slide.

• States of Matter (What’s water made of)

Changes of State/Phase changesThe conversion of a substance from 1 physical form to another• Physical change• Heat energy, particle _________ & _______

changes.• Temperature/KE = the _______of the particles’

motion

MELTING• Change of solid to liquid• Melting _____is the temp. @ which the

change occurs• Most substances have ______ melting

points.• Melting point = ________ point (same

temp.)• Happens because matter ________ energy,

particles ________ apart and move ______.– Heat/NRG stays inside, so ___________ change.

FREEZING• Change of liquid to _________.• Freezing point is the temp. @ which the

change occurs = melting point. Ex. Water freezes and _________ at 0 deg. C.

• Matter releases heat/_______, particles slow down– Heat energy goes out, so _________ change

VAPORIZATION• Any change from liquid to _____• Particles ________ and spread apart.• Matter absorbs NRG, so __________ change(i)_________ : happens throughout the liquid

– _________ point – temp. at which the change occurs

(ii) ______: happens @ the ________of a liquid at all ______, ex. drying clothes outside, puddle ________.

___________

• Change of gas to _____• Condensation point is the temp. @ which

the change occurs• Matter ______ energy, particles ___ ____.– Heat/NRG goes outside, so exothermic change

• Ex. “Dew” and ____ is a form of condensation

___________• Change from solid to _____, never hits

liquid state• Matter absorbs NRG, so _________ change• Ex. _____ ____(frozenCO2)

Deposition

• Phase change from a gas to a _________.

• Particles slow down, move ______ ______-very fast and release heat _____________.____________ change

OQ: Evaporation or boiling?i. Slowerii. Happens at a certain temp. iii. Needs more energy

2/09 p. 22 Phase Changes Notes

• IQ: On your foldable on p. 21 write 2 examples each for solids, liquids, and gases on/by the respective slide.

• States of Matter (What’s water made of)

p. 23 Changes of State/Phase changes

The conversion of a substance from 1 physical form to another• Physical change• Heat energy, particle arrangement &

movement changes.• Temperature/KE = the speed of the particles’

motion

MELTING• Change of solid to liquid• Melting point is the temp. @ which the

change occurs• Most substances have unique melting

points• Melting point = freezing point (same

temp.)• Happens because matter absorbs energy,

particles spread apart and move faster.– Heat/NRG stays inside, so endothermic

change

FREEZING• Change of liquid to solid• Freezing point is the temp. @ which the

change occurs = melting point. Ex. Water freezes and melts at 0 deg. C.

• Matter releases energy, particles slow down– Heat energy goes out, so exothermic change

VAPORIZATION• Any change from liquid to gas• Particles speed up and spread apart.• Matter absorbs NRG, so endothermic change(i)Boiling: happens throughout the liquid – Boiling point – temp. @ which the change occurs

(ii) Evaporation: happens @ the sur- face of a liquid at all temps, ex. drying clothes outside, puddle drying.

CONDENSATION

• Change of gas to liquid• Condensation point is the temp. @ which

the change occurs• Matter releases energy, particles slow

down– Heat/NRG goes outside, so exothermic change

• Ex. “Dew” and fog is a form of condensation

SUBLIMATION• Change from solid to gas, never hits liquid

state• Matter absorbs NRG, so endothermic

change• Ex. dry ice (frozenCO2)

Deposition

• Phase change from a gas to a solid.

• Particles slow down, move closer together very fast and release heat energy.exothermic change

Review

OQ: Evaporation or boiling?i. Slowerii. Happens at a certain temp. iii. Needs more energy

2/10 Phase changes cont’d

IQ: On your phase changes foldable on p. 19, fill in the blanks for phase changes, using your notes.

OQ: Which phase changes did you demonstrate in today’s activity. How could you demonstrate sublimation?

2/11 Phase Changes Graph

IQ: Name all phase changes that take place in the water cycle.

2/10 Water’s phase changes graph

IQ: If the melting point of a substance is higher than the boiling point of water, in what phase will the substance be at room temp.? Explain.

Water

• Water exists on our planet in three states.

• Ice, water, and water vapor

• What causes water to be in one phase or another?

ENERGY

• When energy is added to a substance that energy causes the particles in the substance to move faster and farther apart.

• What happens to the particles when energy is taken away from a substance?

Phase Change

• Energy content is responsible for the different phases of matter.

• Matter can be made to change phase when energy is added to or taken away from a substance.

Melting- Solid to Liquid

• Melting is the changing of a solid to a liquid when the substance absorbs heat energy.

• Melting Point– Water 0° C.– Table salt 801° C.– Diamond 3700° C.

Vaporization- Liquid to Gas

• Vaporization is the changing of a liquid to a gas when the substance absorbs heat energy.

• Vaporization occurring at the surface of a liquid is called evaporation.

Evaporation- a Cooling Process

• As water in the perspiration evaporates from your skin it absorbs and carries away heat energy from your body.

Boiling

• If enough heat energy is applied to a substance particles inside the liquid can change to gas.

• These particles travel to the surface of the liquid and then into the air. This process is called boiling.

Boiling Point

• Boiling Point – temperature at which a substance boils.– Water 100° C.– Table salt 1413° C.– Diamond 4200° C.

• What is the difference between evaporation and boiling?

Gas to Liquid

• Gases can change phase, also in a gas to liquid phase change.

• A substance in the gas phase that loses heat will change to a liquid. This is called

____________.

Condensation

• Water vapor in surrounding air loses heat energy when it comes in contact with the cold glass. Water vapor condenses and becomes liquid drops of water.

Sublimation – Solid to Gas

• Solid to gas phase change occurs when the surface particles of a solid change directly into a gas.

Sublimation – Solid to Gas

• You may notice this in the cold winter with snow. The snow does not melt, but slowly disappears.

• Dry ice goes directly from solid carbon dioxide to gas.

Heat (thermal energy)

Tem

pera

ture

º C

.

100

0

A

B

C

E

solid

liquid

gas

Water Phase Change Graph

Copy the following graph:

D

Discuss with your partner,i) What is happening in each part, A thru E in

the graph. ii) Why is the graph this shape, instead of

having a line with a constant slope?

Block of Ice to Steam

• Block of Ice to Water Vapor• Phase change diagram

Heat (thermal energy)

Tem

pera

ture

º C

.

100

0

A

B

C

DE

melting

freezing

condensing

boiling

Phase Change Diagram

- The graph shows a const. temp. during melting/freezing and boiling/condensation, as during a phase change, the extra heat energy goes towards breaking or creating the intermolecular bonds, so there is no change in the temp./speed of particles but heat is constantly added or lost.

OQ: Which phase change requires more energy? Why do you think that is?

Use the graph below to answer the questionsa. What is the freezing point?b. What is the boiling point?c. At which time interval is the substance a solid?

• OQ: As phase changes occur, heat energy of the substance __________(changes, stays constant), while the temperature __________(changes, stays constant).

Comparing Changes of State

• Changes occur because of an endothermic (NRG is +) or exothermic (NRG is -) change

• + or – NRG changes how the particles in the matter move

These endo- & exothermic changes cause the H2O cycle.

All of the endo- & exothermic changes occur @ specific temps!

Temp Change vs. Change of State

When matter absorbs or loses NRG, it will either change temp or change state.

Temp remains constant until change of state is finished.

Section 2 Review ?s: COMPLETE ANSWERS

1. Compare & contrast endo- & exothermic changes.

2. Describe how the motion & arrangement of particles change as a substance freezes.

3. Compare & contrast boiling & evaporation.

4. After taking a shower, you notice there are droplets of H2O on the mirror. Explain why. Be sure to state where the H2O came from & how it goes from state to state.