Do Now: Silently, independently you 10 minutes If you finish early you may read silently and independently 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!
SWBAT 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 changes 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 change. Endothermic: the system absorbs energy from the surroundings. Example: ice melting. Exothermic: the system releases energy to it’s surroundings Example:?
How are we doing? Name a phase change. What happens to temperature? What are the two types of energy of transfer?
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 mirror. 3. The water molecule condenses on the mirror (exothermic).
Exit Ticket = Summarize Today’s Notes Take the change to review your notes from today. Draw a line and under the line begin a summary. Use your own words! Use pictures!