Why does your glass of cold lemonade "sweat" on a hot day? How can water exist as a solid, liquid and gas on Earth? What happens when you stick your tongue to a cold pole in the middle of winter?
These are the questions that can be explored when working to understand how matter changes states between solids, liquids and gases (don't forget plasma and Bose-Einstein Condensate too) using the particle model of matter. This lesson relates directly to the MS-PS1 Matter and its Interactions performance indicator that asks students to, "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" (MS-PS1-4).
Additionally, this as students demonstrate their understanding of the particulate model, they access important cross cutting concepts and science practices related to:
1) Energy and Matter: Energy may take different forms and the transfer of energy can be tracked as energy flows through a designed or natural system (CCC).
2) System and System Models: Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy, matter, and information flows within systems (SP2 and CCC).
3) Patterns: Macroscopic patterns related to the nature of microscopic-level structure of matter (CCC).
4) Scale, Proportion, and Quantity: Time, space, and energy phenomena can be observed at various scales using models to study systems that are too large or too small (CCC).
Students conduct this investigation to produce data to serve as the basis for evidence that meet the goals of the investigation (SP3) by heating and cooling different liquids to identify the melting/freezing point and boiling points. Students then analyze and interpret data to provide evidence for phenomena (SP4) of changing from one state of matter to another.
This lesson can be used separately, but it also works as a creative assessment strategy to conclude a unit of study about states of matter. The sequence of these related lessons occurs as is follows:
4) Hot and Cold Investigation (This lesson)
In order to ENGAGE students in this lesson, students view the Dry Ice Sublimation video while thinking about the following prompt:
How does this video show different states of matter?
The EXPLORE stage of the lesson is to get students involved in the topic so that they start to build their own understanding. To help students explore changes of state, students familiarize themselves with these changes by formulating the question they will answer in the investigation on the Hot and Cold Investigation lab sheet:
How does adding or removing energy (changing the temperature) affect the state of matter?
Students complete the extensive Background Research section of the investigation. This section is a pivotal part of the process of building conceptual understanding because it introduces and reinforces vocabulary (melting, freezing, boiling, etc); links vocabulary to particle models; and builds a causal relationship between the variables of temperature (energy change) and changes of state.
Students require support during this section of the investigation due to the complexity of the concepts. Support strategies include:
1) Provision of developmentally appropriate and accessible resources (textbook, online resources like: Chem4Kids).
2) Planning for multiple opportunities for students to communicate what they have learned so far and help figuring out what it means. By asking questions and pointing students in the right direction by showing them resources that will help them find the information, students develop their understanding through inquiry. Questioning students presents a great quick formative assessment opportunity for evaluation of students' developing understanding.
3) Review of the concepts as a class using the Change of State Notes. By reviewing and providing students with notes, they can self-assess the quality of their work and accuracy of their understanding.
Upon completion and review of the Background Research section, students move on to plan the rest of their investigation (Part 4). This investigation follows a linear and structured inquiry path (for more discussion of linear versus non-linear scientific inquiry, visit this lesson: Exploring Scientific Methods). For an alternate way to use an investigation such as this one, read this sections' reflection: Turning Inquiry Upside Down.
The EXTEND stage allows students to apply new knowledge to a novel situation. The novel situation in this case is to perform experimental tests and collect data (Part 5 of Hot and Cold Investigation lab sheet). The data collection process has two parts. Student lab groups split into two groups and complete each part concurrently:
1) Part 1: Cold - Students use a mystery liquid (water, salt water, vinegar, isopropyl alcohol, etc.) to cool to the substance's freezing point while collecting temperature readings.
2) Part 2: Hot - Students use the same mystery liquid (water, salt water, vinegar, isopropyl alcohol, etc) to heat to the substance's boiling point while collecting temperature readings.
Upon completion of data collection, students analyze their data by determining the freezing point and boiling point of their mystery liquids. To aid in this process, students graph their data. The resulting coordinate graph (as shown here: Hot and Cold Investigation Coordinate Graphs Student Work) displays the data visually, which shows a pattern of positive slopes and flat slopes (0 slope). The positive slopes correspond to the increasing or decreasing temperature prior to freezing and boiling. The flat slopes correspond to the time when the liquid is in the process of freezing and boiling; temperature does not increase or decrease, thus making this temperature the freezing or boiling point.
Students use their determined freezing and boiling points to identify the type of matter they have using the Clear Liquids Physical and Chemical Properties Chart. Once students make a claim for their matter identification, they move on to provide evidence of their learning in the EVALUATE stage.
Teacher Note: Special safety concerns during this investigation include the use of hot plates, electrical cords and electricity in the presence of liquids, burning and freezing hazards and the use of chemicals. Remind students of general safety expectations and especially of those unique precautions required of this investigation. Goggle wearing, staying at lab tables and assuming all chemicals are hazardous (especially because the liquids in this investigation are unknown) are important to remember. Also, depending on which mystery liquids are used, there may be special considerations. For example, vinegar has a powerful and noxious odor when boiling and must be vented. Isopropyl alcohol is easily ignitable, so small amounts must be used and appropriate fire suppression devices readily available.
The EVALUATION stage is for both students and teachers to determine how much learning and understanding has taken place. At the conclusion of this lesson, students should be able to use the particulate model of matter to explain how different states of matter are a function of the arrangement and energy of the particles in matter.
In order to evaluate understanding, there are multiple methods:
2) This resource can also be used as an evaluation or relearning tool: Changes of State Relearn and Reassessment Activity.
3) Review of student work (Hot and Cold Investigation Student Work) including the analysis questions at the end of the investigation, provides additional insight into students' abilities to explain what they have learned about states of matter.
5) A final way to evaluate student learning is to create a final project following the instructions on page 2 of this version of the investigation: Hot and Cold Alternate Investigation.