Boiling and Freezing Points Lesson 3: Blow It Up With Butane!
Lesson 12 of 12
Objective: Students will be able to explain how solutes and pressure affect the boiling/freezing points of liquids and be able to describe the energy transfer that occurs during phase changes.
This lesson, "Blow It Up With Butane!", is the third of a 3 lesson series. If all aspects of this lab rotation are completed, this series of lessons will take 4 to 5 days to complete.
This lab rotation consists of three very exciting labs that students love! These stations focus on how solutes and pressure can affect the physical properties of the substances involved. However, for me, this set of lessons serves a larger purpose. It is designed as a summative assessment for some scientific literacy pieces that my students have been working on: reading, writing, and group discourse/discussion. Each station, including the reading, writing, and discussion takes about one and a half to two class periods. On the Better Lesson website, each station of this rotation is a separate lesson. The stations/lessons include:
On Day 1: All Hail the Freezing Point, students "flash freeze" a test tube of water! Students drop a small piece of ice into a super-cooled water test tube and the entire test tube freezes instantaneously!
On Day 2: Oh, Boil the Pressure!, students make water freeze at 50 degrees Celcius!
On Day 3 (this lesson): Blow it Up with Butane!, students feel a liquid that is boiling that is cold and makes cool popping sounds!
For each of the lab stations, students must read for information independently and track what they are thinking as they read using reading strategies of "Talking to the Text" and the "Ladder of Discourse". Then, students follow a procedure to complete a lab station featuring an unexplained phenomena. Next, students write a well developed scientific paragraph using a format we call "ABCDE" in which they must cite multiple sources of evidence while they maintain a formal tone. Finally, students partake in group discourse and discussion as they verbally cite textual evidence and qualitative observations to support their ideas. It is truly a culminating event in which students must demonstrate mastery of both scientific content and literacy.
Now, you may be thinking, that is a lot! But, I will tell you, I truly believe this series of lessons is worth looking at. I am confident that whether you use each lesson in its entirety or not, each lesson has something you can use in your own classroom. This set of lessons includes reading and text strategies, scientific writing techniques, cool lab stations/demonstrations, and insight on how to promote deep discussion and discourse from your students. There is something for everyone!
Thus, please keep this in mind when you look at the next section that describes the connections to the NGSS and the Common Core and see the large bundle of standards that this is a set of 4 to 5 days and is a summative assessment of many reading and writing skills.
This series of lessons is designed to reach the following NGSS and Common Core Standards:
MS-PS1-2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
MS-PS1-4 Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
In addition, these lessons connect to a number of literacy Common Core Standards.
Science and Engineering Practices:
When using the text strategies utilized in this lesson, students think deeply about text in order to make their own conclusions and consider solutions to problems. Thus, students are using the Science Practice of Generating Questions and Designing Solutions which states that "Students at any grade level should be able to ask questions of each other about the texts they read, the features of the phenomena they observe, and the conclusions they draw from their models or scientific investigations. For engineering, they should ask questions to define the problem to be solved and to elicit ideas that lead to the constraints and specifications for its solution." (SP1)
In preparation for performing the lab stations, students use strategies to obtain scientific information and evidence from text (SP7). In addition, students back up their explanations in the lab document with evidence from their qualitative observations (SP8).
When students discuss what they see in the lab in comparison to what they read in the text, students can begin to see patterns how adding a solute can affect the properties of solvent. Thus, students can begin to see that macroscopic patterns are related to the nature of microscopic and atomic-level structure (Patterns). In addition, as a part of this lab, the students track how energy is transferred within systems during phase changes (Energy and Matter).
Ask students, "What are you going to learn today?". Students should respond by saying that they will be answering the Essential Question, "How do particles combine into new stubstances? And, what evidence can show how the physical and chemical properties of the substances change?" This EQ is posted on my board and on the student's Chemistry Unit Plan.
Explain that today they are going to begin a series of lab stations that will allow them to demonstrate not only their understanding of physical properties and factors that influence them, but to show their mastery of reading for understanding, writing scientific explanations, and discussing in groups with group discourse techniques. Let students know that their content focus will be Skill 4 on their Chemistry Unit Plan which states "I can identify the physical and chemical properties of the reactants and products in a reaction." Specifically, students are going to pay close attention to physical property changes caused by adding solutes and how energy transfers as matter changes phase.
**It is important to note that my students have already been introduced to physical and chemical properties as well as endothermic and exothermic reactions before this lab. To see their introduction to these concepts, check out the following lessons: Crack that Marble Labs (chemical and physical properties) and Talk About Burning Your Money! (phase changes, energy transfer, endo- and exo- thermic reactions)
Remind students that they should thoroughly read all procedures before beginning this lab station. Emphasize that they are being assessed on their ability to "Talk to the Text" and reach the top rung of the "Ladder of Discourse". Thus, taking time to thoroughly complete step one of the procedure is essential. Once students have completed this procedure, they should begin answering the question from the lab document.
Butane bottles can be purchased at superstores like Meijer. They are sold in pressurized containers with a plastic tip at the end. To get the butane out, you must pinch the plastic tip and pull it in towards the bottle. It is also important to keep away from any source of fire.
1. Read the background knowledge for “Blow it up with Butane!”
2. Close the zip lock bag so that there is only a small opening at the edge.
3. Place the tip of the butane bottle inside the opening.
4. Invert the bottle, and press the tip of the bottle on the table to release the butane inside the bag. Be careful! You don't need a lot!
5. QUICKLY seal the bag shut.
6. Observe the phase change that occurs. Keeping the bag sealed, touch the liquid with your fingers.
There are so many cool things that happen in the bag. Even though it is boiling, the bag feels really cold! And, when students pinch the bag, the gas bubbles produced "pop" in their fingers. Last the zip lock back expands and "blows up"! As shown in the video below, this lab will elicit a lot of fun reactions from your students!
While doing this lab, a student came up to me and asked if they could test to see if butane gas was more or less dense than air. She asked me for two balloons and tested! I love when students are curious about testing their ideas and making connections to science content that is not specifically addressed in this lesson.
Either at the end of the class period or at the beginning of the next class period, have students discuss the Oh Boil, the Pressure! lab station. Students in my class have been working on discussion techniques and using discussion/sentence starters to improve group discourse. (For a look into one strategy I use to help develop this skill, check out the Fishbowl Activity in the S'mores Lesson.) The videos below show some of my students going through some discussions.
Ask the students to participate in a group discussion about the following:
1. How could the bag feel cold if it was boiling?
2. Look at the container that butane is sold in. Explain why you think it is in that type of container.
Take a look at some of my students/ discussions.
Once students have completed their ABCDE paragraphs, have students conclude the lesson by peer editing their responses. When peer editing, I use a process I call, "Put Your Finger On It". I provide the students with a checklist of items they should be able find in their peer's writing (Checklist is included in resources). For each item, they have to physically touch it with their finger. If they cannot physically touch it, they provide their peer with feedback about what they are missing so that student can make corrections.
It is important to emphasize and follow through that the students are actually touching the paper with their fingers. In my experience, students just check things off the list. As students peer edit, I ask them to show me where they actually found items on the list. Physically touching the paper to find the important items increases the student feedback.
Allow students to have time to make the revisions necessary based on their peer's feedback.
This video shows you student work at every rung of the "Ladder of Discourse". It also goes through the "talking to the text" strategy for every station in this lab rotation.
Student work, Common Student Challenges, and Peer Editing found in the student work from Blow It Up With Butane.