Boiling and Freezing Points Lesson 1: All Hail the Freezing Point!
Lesson 10 of 12
Objective: The students will be able to explain how solutes and pressure affect the boiling/freezing points of liquids and describe the energy transfer that occurs during phase changes.
This lesson, "All Hail the Freezing Point!", is the first 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 BetterLesson website, each station of this rotation is a separate lesson. The stations/lessons include:
On Day 1 (this lesson): 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 Celsius!
On Day 3: Blow it Up with Butane!, students feel a cold liquid that is boiling, 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 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 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).
Explain to students that this series of lab rotations will be their opportunity to demonstrate scientific literacy. I let my students know that I am not only going to be assessing them on their understanding of the science content but on their ability to read, write, and speak like a scientist as well. Explain that for each of the three stations they are going to complete they must use the strategies we have been working on in class to demonstrate mastery in these areas.
First, make students aware that they will be assessed on their ability to read for understanding as they "talk to the text" and climb "The Ladder of Discourse". These are both strategies that the students have been practicing throughout this unit. When reading, students mark up their paper and write what they are thinking as they read ("Talk to the Text"). As they write their thoughts in the margins/on sticky notes, they must demonstrate deep connections to science and the text by climbing "The Ladder of Discourse". Each "rung" of the ladder increases in complexity of understanding. The levels of the ladder are "Tweets" (text to self connections), "Huh?'s"(questions or concepts they do not understand), "Found It" (finding answers to questions through context clues or finding science answers), and "Discourse" (combining ideas to think beyond the text). My reflection demonstrates a look at students work produced in this lesson.
For more background on "talking to the text" and the "Ladder of Discourse" check out the following lessons. These lessons include videos of me demonstrating these strategies and student work:
I remind students that they have been working on "sounding like a scientist" as they write. I explain that as they continue to develop that the format of their writing will become more and more complex. Emphasize that scientists value evidence in their arguments and explanations. And, scientists cite multiple sources of evidence to strengthen their claims. Scientists combine evidence from data, qualitative observations in the lab, text, diagrams, and real world phenomena to make the strongest arguments they can.
Thus, explanations do not always follow the ABCDE format that the students have been using. As scientific writing gets more complex, students should be citing from multiple sources of evidence. So, if a student was going to cite three sources, it could mean that their paragraphs may be "ABCDCDCDE" or "ABCCDDCDE". There is no concrete format. Scientific writers just know that they need to cite enough evidence to strengthen their arguments and include the elements of technical writing. As a result, their does not have to be one cookie cutter writing format. As long as students include these elements, their writing will be effective.
Review the aspects of a well developed paragraph:
A - Assertion - Write a claim. Introduce the argument or explanation.
B - Background - Provide the reader with information they will need to understand your explanation. Often, this is letting the reader know what was done in the lab.
C - Citation - Pull evidence from a text to support your claim. Cite this text by title. Pull evidence from data tables or graphs. Cite these by title and be sure to compare two data points with units when including data. Cite multiple sources of information!
D - Discussion - Discuss how the lab supports the claim by making connections to the information that was cited in the "C" section. With a more complex writing piece there could be multiple points of discussion made.
E - End - Write a conclusion sentence that ties back to the claim.
As this is a summative experience for my students, I praise them for all of the work and growth they have made in scientific literacy over the course of the school year and that I know they are ready to demonstrate independence in this area. I tell them how excited I am to watch them in showing their scientific literacy and that I can't wait to see their reading and writing over the next days!
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. In this lab, students put test tubes of water in two different beakers of ice, one with salt in the ice and one without. Students measure the temperature of the water in the test tubes and find the test tube in the beaker with ice and salt gets much colder than the beaker with just ice. This is due to the fact that the salt lowers the freezing point, melts the ice (melting is endothermic), and thus takes energy from its surroundings (the test tube being part of the surroundings).
1. Read the background reading for All Hail the Dew Point.
2. Cover the bottom of a beaker with a thin layer of salt to the bottom of a 100 mL beaker. Add a little bit of water to the bottom of a beaker; add just enough to cover the salt. Stir the solution to dissolve some of the salt.
3. In another beaker, add the same amount of water.
4. Fill two clean test tubes about 2/3 of the way with water. (Small test tubes; I use 10 mL tubes)
5. Place the test tubes in the beakers.
6. Place a thermometer in each test tube.
7. Record the initial temperatures.
8. Fill each beaker to the top with crushed ice, but don’t get any ice in the test tubes. Stir the mixture with the test tube once a minute for three minutes. If ice falls out when you stir, add it back to the beaker! After three minutes record the temperatures from each beaker.
9. Just for fun…Remove the test tube from the beaker and drop a small ice chip into the test tube.
Let students know that step nine should elicit a strong reaction. And, that sometimes it doesn't work perfectly. If dropping the ice chip into the test tube does not freeze the water instantaneously, they should try it again! Some groups of students might have to try this step 2 or 3 times. One tip that will help them is that there needs to be ice surrounding the test tube at all times. Thus, if ice falls out during stirring or if the ice melts too much, they should add more ice. They do not need to record the temperature each time they try, they are just trying to get the test tube to "flash" freeze. Moreover, they don't need to dump out the beaker with ice and salt with each attempt. If the ice chip doesn't cause this reaction, they only need to dump out the water in the test tube, get fresh water, and stir it in the salt/ice beaker for another few minutes. The timing is everything. You want to get the water just at the verge of freezing. If you don't wait enough time, nothing will happen. If you wait too long, the water in the test tube freezes before you even put in the ice chip. Step nine of the procedure is the exciting part of this lab station! Give students the chance to keep trying until they get it! I would also highly recommend that you practice this yourself before doing this lab so you have an idea of how it works.
Once students have completed this procedure, they should begin answering the question from the lab document.
Teacher Set up:
Each group will require the following set up:
I included three different videos of Step 9 of the procedure. It can be tricky and can present itself differently in each instance. But, it is truly awesome when it happens! You should practice this before teaching this lesson. Sometimes, students will need help with getting it "right".
The student lab document is organized to increase in complexity with each station. Thus, this first station has students fill in the blanks within a pre-written ABCDE paragraph. As a result, their writing goes pretty quickly with this station. The following station requires more writing time. For a closer look at this writing, see the "A Look at Student Work" section of this lesson.
Getting the reaction at the end to "work" takes practice! The video below is one more look at some things that could go wrong and how to fix it. This reaction is well worth the wait and practice! It is really awesome!
Either at the end of the class period or at the beginning of the next class period, have students discuss the All Hail the Dew Point Lab. Students in my class have been working on discourse 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.
Question 1: Why did adding salt to the ice make the water in the test tube colder?
Question 2: Identify the ABCDE in your All Hail the Dew Point paragraph.
*The written responses for these labs build in complexity and independence with each lab station. This first lab station is an ABCDE paragraph with fill in the blanks. Students are always able to fill in these blanks, but I like to take time for them to go through this paragraph and identify the key pieces that would make this paragraph a well constructed scientific writing piece. This will be especially important for students as the questions get more complex with the upcoming stations.
In the video below, students identify the pieces of the paragraph. There are a couple of observations that are key for the students to make. One, the "B", or background, often describes what the students use in the lab. However, in this paragraph, students notice that the background simply gives the reader scientific content information that they will need to know to understand the explanation. In addition, students need to pick up on the complexity of the writing. Students should notice that this paragraph is more like "ABCDCDCDE" as the student in the video below demonstrates. As students grow in their writing, they should recognize the use of multiple citations and that great writing only includes key elements; it does not have to always be "cookie cutter" ABCDE.
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 examines 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, ABCDE Structure and Adapted Version of Lab from All Hail the Freezing Point are examined here: