Do Now:
• Silently, independently you 10 minutes
• If you finish early you may read silently and
• Have your homework out on the top right corner
of your desk.
• Today’s Topic: PHASE CHANGES!
Let’s Review…
Class Updates!
• Those that need to take the test/quiz need to do it by
the end of this week! NO EXCUSES!
• Don’t forget about participation tickets!
• Extra credit will be given for boxes of tissue
• I also have binders (only 8 for sale) for those of you still
do not have a binder for my class!
• Describe each of the six phase changes.
• Identify phase changes as endothermic or exothermic.
• By the end of the day you will be able to answer the
following question: why does steam collect on the
mirrors during a shower/bath?
Let’s what some heat transfer and phase
• Predict what you think will happen
• Write your observations in your notes
• Tea bag
• Why?
• Think-Pair-Share
Phase Change!
• Is a reversible physical change that occurs when a
substance changes from one state of matter to another.
• Melting
• Freezing
• Vaporization
• Condensation
• Sublimation
• Deposition
Temperature & Phase Changes
Temperature of a substance DOES NOT
change during a phase change.
Energy Transfer
• Energy is either absorbed or released during a phase
• Endothermic: the system absorbs energy from the
• Example: ice melting.
• Exothermic: the system releases energy to it’s
• Example:?
How are we doing?
•Name a phase change.
•What happens to temperature?
•What are the two types of energy of
Melting & Freezing
The arrangement of molecules in water becomes less orderly as water melts and more
orderly as water freezes
• Melting: increase in average kinetic energy because energy (as heat) is added
to the system and they begin to vibrate more quickly, until melting happens.
• Example: ice-cream melting
• Freezing: decrease in average kinetic energy because energy (as heat) leaves
the system, thus molecules begin to slow until an orderly arrangement (frozen).
• Example: an ice cube!
Vaporization & Condensation
Vaporization: when changes from a liquid to a gas
• Endothermic process, meaning?
• Example: The refrigerators use evaporators to keep food cold
Evaporation is the process that changes a substance from a liquid to a gas at temperatures
below the substance’s boiling point.
• Example: puddles of rain disappear a few hours after a storm.
Boiling: takes place throughout a liquid, both the temperature and the vapor pressure of
the water increases.
• Kinetic energy increases!
What vapor pressure?
• The pressure caused by the collisions of vapor particles on a container!
Vaporization & Condensation Continued
• Condensation: is the phase change in which a substance
changes from a gas or vapor to a liquid.
• Example: the steam on your bathroom mirror.
• This is because water vapor cooled as it came in
contact with the mirror. The water vapor transferred
heat to the mirror and CONDENSED into a liquid.
• It is an exothermic process.
Sublimation & Deposition
• Sublimation: is the phase change in which a
substance changes from a solid to a gas or vapor
without changing to a liquid at first.
• This is an endothermic process
• Examples: as dry ice melts, it sublimes because
the cold carbon dioxide vapor causes the water
vapor in the air to condense and form clouds
Sublimation & Deposition Continued…
• Deposition: when a gas or a vapor changes directly into
a solid without first changing into a liquid.
• This is an exothermic process (reverse of sublimation).
• Examples: frost forming on windows, because when
water vapor contacts windows it looses enough energy
to change from a gas to a solid.
Let’s Watch a Video!
Essential Question Answered
•So… why is there a ‘cloud’ on the mirror in the
bathroom after a shower?
• 1. The water molecule on the surface of the bath
water evaporates (endothermic).
• 2. Random motion carries it the surface of the
• 3. The water molecule condenses on the mirror
Exit Ticket = Summarize Today’s Notes
•Take the change to review your notes from
•Draw a line and under the line begin a
•Use your own words!
•Use pictures!

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