P h a s e C h a n g e I n s t r uc ti o n a l C a s e : A s er i e s o f s t u de n t -c e nt er e d s c i e nc e l es s o ns Lesson 1 Molecular Motion Shaker Box Summary Suggested Timeline 45 minutes Materials 3 CD cases per group 2 different colored pony beads “Molecular Motion” probe Prep 1. Set up each group with 3 CD cases, 2 different colored pony beads, and 1 copy of the Molecular Motion probe. 2. The CD cases should represent 3 states of matter. Objective(s) Students learn that matter exists in moving particles and the freedom of movement of these particles depends upon the state of matter. An increase in temperature results in a greater movement of the particles. Phase Change Instructional Case Lesson 1 This lesson is an introduction to molecular motion within the three different states of matter: solid, liquid and gas. The teacher will elicit students’ prior knowledge on the subject by using a probe to understand students’ misconceptions. Students will be manipulating three conceptual models and then will continue to manipulate and revise the model based on how temperature affects particle motion. Lesson 0 on modeling can be a great way to introduce students to the concept of modeling as a science and engineering practice. Teacher Background Knowledge Atoms and molecules are in constant motion. In a solid, the particles vibrate in place in fixed positions that maximize the attraction between them. As the temperature of a solid increases to a temperature that is just below its melting point, the molecules vibrate faster in their fixed positions. In a liquid, the attractions between molecules are still relatively strong (compared to the gas state), but the position of individual molecules is no longer fixed. Thus, liquids have the ability to flow and take the shape of their container. In the gas state, molecules have enough energy to move independently at high speeds undergoing frequent collisions. In each of the three states of matter, as temperature increases, so does the kinetic energy (motion) of the molecules. As you increase the amount of shaking, you increase the amount of motion and thus, increase temperature. The shaking of the container mimics the addition of thermal energy and breaks the attraction between the molecules. The model has the advantage of showing how density is often different. The teacher can address this concept and dispel the misconception that it is the number of molecules that differentiate solids, liquids and gases. You would expect there to be significantly fewer particles in the same volume of gas than of a solid, for instance, when discussing the concept of density. The advantage of using pony beads is that you are seeing interactions and degrees of freedom available to the particles in the different states of matter. Page 2 of 4 Lesson 1 Molecular Motion Shaker Box Standards 12 NGSS Performance Expectations: This lesson supports students in progressing toward the NGSS Performance Expectation. MS-PS 1-4: 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. Emphasis is on qualitative molecular-level models of solids, liquids, and gases to show that adding or removing thermal energy increases or decreases kinetic energy of the particles until a change of state occurs. Examples of models could include drawings and diagrams. Examples of particles could include molecules or inert atoms. Examples of pure substances could include water, carbon dioxide, and helium. MS-PS 1-5: Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved. Emphasis is on law of conservation of matter and on physical models or drawings, including digital forms that represent atoms. Assessment Boundaries: Assessment does not include the use of atomic masses, balancing symbolic equations, or intermolecular forces. In this lesson… 1 Science and Engineering Practices Disciplinary Core Ideas Cross Cutting Concepts Developing and Using Models: Use model of the CD cases and pony beads to compare and evaluate the three different states of matter. Use the model to describe the phenomena of phase transition. PS1.A: Structure and Properties of Matter Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter. Cause and Effect Use the model to predict phenomena in the designed system of the CD cases. Observe how shaking and tilting the case affects the pony beads. Listen for observations. Energy and Matter Matter is conserved because atoms are conserved in physical and chemical processes. Note that no pony beads were gained or lost during the entire activity. NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, D.C.: The National Academies Press. 2 National Governors Association Center for Best Practices, Council of Chief State School Officers Title: Common Core State Standards (insert specific content area if you are using only one) Publisher: National Governors Association Center for Best Practices, Council of Chief State School Officers, Washington D.C. Copyright Date: 2010 Page 3 of 4 Lesson 1 Molecular Motion Shaker Box In this lesson… CCSS Mathematics CCSS English-Language Arts MP.2 Reason abstractly and quantitatively. SL8.1C Pose questions that connect the ideas of several speakers and respond to others’ questions and comments with relevant evidence, observations, and ideas. 8.F.B.5 Start preparing students to think about the qualitative relationship between temperature, time and phase transition. Prior Knowledge In grades 3-5, students have learned that because matter exists as particles that are too small to see, matter is always conserved even if it seems to disappear. Before this lesson, students must have been introduced to the idea that all matter is made up of particles (atoms or molecules) that are so small we cannot see them directly. It is not necessary that students understand the difference between atoms and molecules, only that matter is made up of small particles we cannot see. If students are not familiar with this idea, briefly state that all matter is made up of small particles we cannot see; water, for instance, is made up of individual particles of water called molecules. Lesson 1. *Introduction to Modeling*: Have students understand the five important points in building conceptual models. Students can differentiate between the model and the real thing, evaluating the model and its limitations. 2. Probe: Start the lesson by giving the students the Molecular Motion Probe. This probe allows you to gauge common misconceptions your students may have about molecular motion. (If necessary, briefly explain that “molecule” is a term for a very small particle of matter we cannot see). After students have responded silently to the probe in writing, ask students to go to one of four corners of the room based on their response to the probe. 3. Ask students to explain to one other person in their corner their choice and then listen while their partner explains their reasoning for the choice. Begin a class discussion about the reasoning for choosing each of the four models. Possible questions for whole-class discussion: “How does this model help explain what we observe when substances are heated?” “Why is this model better than the others?” “What kinds of things would we expect to observe if this is what particles actually do when heated?” “How could we test this model?” 4. Tell students that they will now investigate the effects of an increase in temperature on particles (molecules) by using actual models of solid, liquid, and gas states of matter. Distribute the CD cases to groups of 2-4 students. 5. Activity: Have students shake it, tilt it, and listen to each CD case. Have students first draw each case. Underneath the drawings of each case, students write down their detailed observations, keeping in mind what happens as they shake it, tilt it, and listen to it. Page 4 of 4 Lesson 1 Molecular Motion Shaker Box 6. Questions to focus on: Which case best represents a solid, liquid, or gas? Why? What happens to the overall pattern or arrangement of beads when the case is moved? How might a higher temperature change this motion? What can you do with the CD cases to show a higher temperature? Which model from the probe (A, B, C, D) is most like the CD case model of particle motion? Potential Pitfalls The CD case models by themselves do not demonstrate that particles are always motion; latter activities in the unit do demonstrate this key idea.