Lesson: Changing States of Matter

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Lesson Objective

Students will record notes about the 6 processes that change one state of matter into another state of matter.

Lesson Plan


  • Chart (*whiteboard may be best):
  • (in a triangle formation): Gas on top, Solid (bottom left), Liquid (bottom right).  Draw 2-way arrows for the sides of the triangle.



  • Ask: What are the 3 states of matter?
  • Solid, Liquid, Gas
  • Ask: What happened yesterday with our slushie experiment?
  • The ________ started out as a _________ and ended up changing into a ________.
  • The ice started out as a solid and ended up changing into a liquid.
  • The juice started out as a liquid and ended up changing into a liquid.
Ask: What happened to the ice?                It melted. Ask: When do things usually melt?    In the sun.
  • Why? Because it’s hot.
Ask: Can I turn water back into a solid?     How, what is that called?              Freeze it. Today we will learn the process (or the way) that states change from one state to another. Pass out student response sheets.



  • For each of theses processes, we will be writing about how it happens and we will be drawing a small sketch to illustrate the process.
  • Point to the first process Sollid -> Liquid.
  • Say: When a solid transforms (or changes) into a liquid, it is called melting. Melting happens when you add heat to a solid. If I bring ice outside into the hot sun, it will melt into liquid water.
  • Sketch: ice cube + heat from the sun = puddle of water.
  • Have students turn to their partner and teach them what melting is.
  • Call on a student to tell the class what melting is.
  • Have students fill in the melting box.
Point to the 2nd process: Liquid -> Solid
  • Say: the antonym (or opposite) of melting is freezing. Freezing happens when you take away* heat from liquid. If I put water in a freezer, the liquid water will turn into solid water à ice.
  • Sketch: puddle of water + freezer =  ice cube
  • *Students may be unfamiliar with this concept, it is important for them to know that we can’t add “cold” to something. We either have heat added or heat removed from an object.
  • Have students turn to their partner and tell them the difference between freezing and melting.
  • Call on a student to tell the class what freezing is.
  • Have students fill in the freezing box.
Point to the 3rd process: Liquid -> Gas
  • Say: When you add head to a liquid, the liquid evaporates into a gas. If I put a pot of water on the stove and heat it, what starts to travel up out of the pot? Gas or steam.
  • Sketch: pot of water + stovetop =  steam
  • Have students turn to their partner and tell them another way to get water (or another liquid) to evaporate.             
  • Leave it outside in the sun.
  • Call on a student to tell the class what evaporation is.
  • Have students fill in the evaporation box.
Point to the 4th process: Gas -> Liquid
  • Say: When gas is cooled, it turns into a liquid. The gas condenses into liquid. Overnight the air cools and water condenses onto the grass or on the window. These drops came from the condensation from air.
  • Sketch: air + cooling =  dew drops
  • Have students turn to their partner and tell them where else they these little drops of water come from.               Clouds à Rain
  • Call on a student to tell the class what condensation is.
  • Have students fill in the condensation box.
Pause to tell the students that these first four processes are the main ones that happen a lot and that we have seen before. Most of the time if a gas turns to a solid, it will first cool to a liquid, then that liquid freezes into a solid. These last 2 processes, skip the liquid step and go straight from a gas into a solid or a solid into a gas. Point to the 5th process: Gas -> Solid
  • Say: When gas is cooled very fast, it skips the liquid step and turns into a solid. This is called Deposition. When the temperature is extremely low, the water vapor (gas) in a cloud can turn into snow (solid) or frost (solid) on a window).
  • Sketch: cloud + cold =  snowball/snowflake
  • Have students ask their partner what gas needs to skip turning into a liquid and go straight to a solid.     It needs very low temperatures.
  • Call on a student to tell the class what deposition is.
  • Have students fill in the deposition box.
Point to the 6th process: Solid -> Gas
  • Say: When some solids are heated, they go through sublimation to change into a gas. The solid sublimes into a gas. 
  • Sketch: dry ice* + heat =  Carbon Dioxide gas
  • Have students turn to their partner and ask them if sublimation turns a solid into liquid or a solid straight into a gas.
  • Call on a student to tell the class what sublimation is.
  • Have students fill in the sublimation box.
  • *It might be helpful to show a picture of dry ice, if the students haven’t heard of it. Or an optional demonstration would support their understanding of this process.



  • Tell the students that today they learn 6 different processes that explain how states of matter change from one into the other. When they go home, they should think of other ways that they might have experienced any of these processes. Can other things melt? How? What else can freeze? How? Have they seen evaporation anywhere else? Have they seen condensation on any other objects?
  • Tomorrow we will be playing a musical activity to explore how the atoms in these states move around!



This is a heavy "lecture" lesson that I rarely do in my lessons, but there is so much information that I prefer to just diagram the whole thing and then explain key concepts (melting/freezing, evaporation/condensation). So many of these processes are invisible to the students' eyes. Students should know that there is a very real process that makes the states of matter go from one state into the other. I am looking forward to bringing in a little more demonstration to illustrate these processes to my students in the future (e.g. dry ice). 

Lesson Resources



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