Investigating Change of State
Lesson 2 of 10
Objective: SWBAT identify matter at it's various phases and describe how the particles too small to see are changing as the matter changes state.
The Why Behind Teaching This:
Unit 2 addresses standards related to matter and it's interactions. The unit begins with identifying types of matter and the particles that make it up. This is covered in standard 5-PS1-1: Developing a model to describe that matter is made of particles too small to be seen. We will be changing matter by melting, evaporating, and dissolving to prove that although the physical appearance has changed, the same amount of matter still exists. This is covered in standard 5-PS1-2: Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved. We will also be using a variety of properties to identify matter through standard 5-PS!-3: Make observations and measurements to identify materials based on their properties. The investigations and experiments during this unit will focus on physical and chemical changes that occur when mixing matter which addressed in standard 5-PS1-4: Conduct an investigation to determine whether the mixing of two or more substances results in a new substance.
This specific lesson is related to standard 5-PS1-2: Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of the matter is conserved. This entire lesson focuses on the changes of state and what adding heat does to the particles. I do not get into the conservation of mass during the process. The target of the lesson is to provide them with background knowledge on how heat affects the particles, so that they can relate this to future concepts in this unit such as dissolving and physical changes.
The goal of this lesson is for students to be able to identify how adding heat, and taking heat away, affects the unseen particles in matter that causes it to change state.
Students will demonstrate an understanding of how heat affects particles by acting out the motion of particles at the conclusion of the lesson.
Preparing for Lesson:
- Have a cup and ice ready for each group. They will be racing to melt the piece of ice.
You will be drawing diagrams of the particles in the states of matter during the discussion. You will need the whiteboard, or science notebook under the document camera on the overhead.
You will need the following items for the explore activity:
- a burner
- a pot
- 8 - 10 pieces of ice
Open space for students to move while they act out changes in matter.
The Purpose Behind the Race:
I open the lesson with a fun ice melting race to help students make a connection between melting (changing state) and heat. Although this has not been taught, students already have an understanding that heat is what causes matter to change state. They observe this in their everyday lives when they eat ice cream outside, puts ice in their drink and it melts, etc. I want them to pull in some of that background knowledge when trying to melt their ice without any help from me. I like to see what creative ways they come up with to melt it.
Students Cause Matter to Change State:
I provide each group with a cup that contains one piece of ice. I give them the task of melting the ice as fast as they can without touching the ice. Those are the only directions that I give as I like to see the methods students come up with. I have some groups shaking the cup, several groups breathing in the cups, one group gets up and goes to the sink to add water to the cup, and finally I have a group take their cup over to the microwave to heat it up.
The Video of students racing to melt ice shows how all groups begin by shaking and breathing in the cups.
Video 2 of students racing to melt ice shows one group decide to take it the cup to the sink, and after seeing that, another group races over to the microwave to melt their ice. After the group microwaves it, the ice is melted within seconds and the activity ends.
Making the Connection to Heat:
I ask one person from each group dump their ice and water in the sink and return their cup to the table. While they are doing this, I review the methods used by groups to melt the ice: some groups shook the cups, some were breathing in the cups, one group added water, and then one used the microwave. I ask what all of these methods have in common, what all groups were trying to do. Students tell me they were all trying to add heat to melt it the fastest. This connection between heat and melting, leads into our lesson for the day about how heat affects the particles in matter.
Reviewing Properties of Each State of Matter:
I take about 10 minutes to review the states of matter and how particles are arranged and moving in each. I specifically call on students who did not demonstrate an understanding of these concepts on the model or the exit ticket from the first lesson on states of matter.
I ask students to describe how the particles are arranged in a solid and I draw a diagram on the whiteboard in front of the class. I ask students how particles are arranged in a liquid and I draw a diagram to model this as well. Students also describe the particles in a gas and I add a diagram of this. We discuss the differences between how the particles are arranged and how they are moving in the three states.
Students explain that the particles in a solid are tightly packed and arranged in rows. I ask why they are so tightly packed so that we review the strong bond holding them in place. I ask students to describe how this tight bond and arrangement of particles affects the properties and movement of a solid. Students tell me that solids are hard, they do not take the shape of the container they are in, they can break. I ask them how the particles are moving and many of the students tell me that they can't move. I tell them that all particles have energy, so they are moving. I point out one of the particles on the board and ask the students what it would look like if that particle was moving but had no where to go. A student in the front begin shaking back and forth, I point him out and say "Yes! Exactly!" The particles in a solid can't break that bond so they just vibrate in place next to each other.
We then move onto liquids as I point to the diagram I drew on the board. I ask how the particle arrangement changes from a solid to a liquid. Students tell me that the bond gets weaker which allows the particles to spread apart more. They also add that particles are no longer arranged in rows but instead move around freely. I ask how this motion of particles affects their properties. They tell me that liquids can flow and take the shape of any container they are put in.
I then point to the diagram of a gas and have them explain how the particle arrangement in a gas is different. They say that the bond is very weak so the particles can fly around anywhere and there is a lot of space between them. I ask how this affects their properties. Students tell me that gases can full any space, we review the word compressed, and also have to review the fact that this is the only state that can change volume. Both solids and liquids maintain the same volume.
Understanding particle arrangement is an important concept for students to understand as they will be referring back to it as we investigate how heat causes these changes in the activity today. It was taught in the first lesson, but spending time reviewing it will add so much to the lesson for today, it is worth taking the time to review.
Solid (ice) Changing to a Liquid (water):
I place several pieces of ice into a pot and walk around so the students can all see it. I ask students to discuss properties of the ice with their group and create a list of properties on a white board.
I place the pot on a burner and allow it to melt as we discuss the properties that groups have listed on their boards. We discuss the arrangement of particles and how the ice has held its shape (cube shaped and solid are two properties most groups wrote down). After discussing this, I go to the burner, remove the pot, and circulate around the room once again to show them what the ice looks like now. It is no longer ice, but liquid water. I ask groups to look back at the properties listed on their boards and identify some properties that have changed. They tell me it is no longer a solid but now a liquid, it is no longer cube shaped but has taken the shape of the container, is no longer cold but is now warm. I ask them what has remained the same, they say it is still clear and it is still water.
I place the pot back on the burner to continue heating it. I move to the whiteboard where I point out the particle arrangement in the diagrams I drew earlier in the lesson. I ask students to compare and contrast the particle arrangement in both a solid (ice) and liquid (water). We continue discussing how the particles are more spread out, and are now moving freely instead of vibrating in place. I stress that the particles themselves have not changed, the ice is made of the particles hydrogen and oxygen, and that the water is still made up of the same particles, they are just arranged differently now.
Students turn to the States of matter foldable that was glued into their notebooks in the last lesson. I draw a large arrow on the whiteboard going from a solid to a liquid and write the term "melt" inside the arrow. I also write "add heat" below the arrow indicating what causes the change. As students copy this into their notebooks, I call one group up at a time to observe the change taking place in the pot.
Liquid (water) Changing to Gas (water vapor):
As groups come up to see the change that is occurring inside the pot, I ask them to discuss in their groups what is happening to the particles in the water causing the change. After all groups have come up to observe the water boiling and steam rising from the pot, I circulate to listen to conversations while they record their thoughts on white boards. Most conversations are still focused on the water beginning to boil so I have to redirect them to think about what is happening to the particles. Each group shares their thoughts.
Students discuss how the particles are spreading apart and moving faster. I ask them how they know this, what evidence did they see that led them to this conclusion. Students tell me that the liquid changed to a gas, the steam. I check for understanding about the particles by asking students what makes up the steam. Although it is now a gas, it is still hydrogen and oxygen. Students are able to tell me this. After our discussion about changes in the particle arrangements and movement, I add an arrow from the liquid to the gas and label it as evaporating along with the note that we added heat. Students copy this in their notebook next to their foldable.
Gas (water vapor) Changing to Liquid (water):
I get a cold bottle of water out of the refrigerator and hold it over the steam. Condensation immediately covers the bottle. I walk around and let students rub the water off the outside of the bottle. I ask them to discuss in groups how that water got there as my bottle is not leaking. I circulate and listen to conversations. I hear one group having a really good conversation about how the bottle cooled off the steam and it changed back into water. I ask that group to share their thoughts with the class and then I reinforce what they say by modeling the process on the whiteboard. I add an arrow going from the gas to the liquid diagram on the board and label it condensing. I ask students what caused this change to happen, did it also require heat? They tell me we cooled it off, or removed heat from it. I label this step as removing heat.
Liquid (water) Changing to Solid (ice):
I do not model the last step as it would require over night to refreeze the water. I simply ask students what would happen to the water if we continued to remove heat to the point that it was 0 degrees Celsius. They said it would turn back into a solid, or freeze. I draw an arrow on the whiteboard going from the liquid to the solid step and label it as "freezing" and below that indicate that it requires removing heat.
Wrapping It Up By Acting It Out:
Since this lesson was whole group and required the students sitting for the the majority of the lesson, I use an activity with movement to wrap it up. I take them outside to get out of the room for a little while. I tell them that they cannot talk to each other but must act out what I tell them to in a group as if each group member is a separate particle in matter.
I call group one up and ask them to act out what the particles in a solid would look like. I am hoping to see them stand close together and model vibrating by shaking their bodies against each other. I say the word melting, and check for understanding that the particles would move away from each other and continue slowly moving around. This video of melting shows that the students understood that the particles in a solid are close together and as heat is added to cause melting they move apart. However, they did not demonstrate an understanding that the particles are constantly in motion, vibrating as a solid, and sliding past each other as a liquid.
I ask that group to sit, and call up group two. I ask them to demonstrate how the particles in a gas would move. I would like to see hey start running around quickly. I ask them to demonstrate condensing and hope to see them start walking slowly and come back closer together in the front of the room. You can see from the video of condensing that the boys in the video are aware of the space and motion of a gas, but either aren't clear on what happens during condensing, or don't know how the particles in a liquid move. They came back close together and just stopped moving when they were suppose to be a liquid.
They sit and I call up group three. I ask them to demonstrate a liquid, and hope to see them moving slowly around with a little space between them. I ask them to model freezing and am watching to see that they come close together and vibrate. The video of freezing shows that the girls understand that as a liquid they are moving around, although I do think they were moving too fast and with too much space between them. It also shows they have a good understanding of how the particles react when they are cooled enough to freezing because they all came close together and were vibrating.
Group three returns to their seats and I call up group four. I ask them to demonstrate how the particles in a liquid move. They should be moving slowly around just as the other group did for a liquid. I ask them to demonstrate evaporation, and hope to see them begin running around the space. The video of evaporating shows that this group had a good understanding of how the particles act in both a liquid and a gas when it evaporates.