Andrew Janisse GK-12 “5E” Theme Based Lesson Plan for
“Heating and Cooling Atoms”
Topic:
What happens to materials when they are heated on an atomic level and how does that affect properties?
National Science Education Standards:
SCIENCE AS INQUIRY STANDARD (9-12) Abilities necessary to do scientific inquiry, and understanding about scientific inquiry
PHYSICAL SCIENCE STANDARDS (9-12) Structure of atoms. Structure and properties of matter.
SCIENCE AND TECHNOLOGY STANDARDS (9-12) Understanding about science and technology
MS Science Framework:
CHEMISTRY: 1c INQUIRY Demonstrate the use of scientific inquiry and methods to formulate, conduct, and evaluate laboratory investigations (e.g., hypotheses, experimental design, observations, data analyses, interpretations, theory development). (DOK 3)
2a PHYSICAL SCIENCE Describe and classify matter based on physical and chemical properties and interactions between molecules or atoms. (DOK 1) Including: physical properties (e.g., melting points, densities, boiling points) of a variety of substances, substances and mixtures, and the three states of matter in terms of internal energy, molecular motion, and the phase transitions between them
2e PHYSICAL SCIENCE Compare the properties of compounds according to their type of bonding. (DOK 1) Which include: 1) covalent, ionic, and metallic bonding, 2) Polar and non-polar covalent bonding, 3) valence electrons and bonding atoms.
2f PHYSICAL SCIENCE Compare different types of intermolecular forces and explain the relationship between intermolecular forces, boiling points, and vapor pressure when comparing differences in properties of pure substances. (DOK 1)
4a PHYSICAL SCIENCE Analyze the nature and behavior of gaseous, liquid, and solid substances using the kinetic molecular theory. (DOK 3)
ORGANIC CHEMISTRY: 1a INQUIRY Conduct a scientific investigation demonstrating safe procedures and proper care of laboratory equipment. (DOK 2) Including: safety rules and symbols, proper use and care of the compound light microscope, slides, chemicals, and accuracy and precision in using graduated cylinders, balances, beakers, thermometers, and rulers.
1g INQUIRY: Communicate and defend a scientific argument in oral, written, and graphic form. (DOK 3)
2f PHYSICAL SCIENCE Relate structure to physical and chemical properties of hydrocarbon. (DOK 1)
3b PHYSICAL SCIENCE Develop a logical argument supporting the use of organic chemicals and their application in industry, drug manufacture, and biological chemistry. (DOK 1)
Objectives:
Students must be able to recognize and observe that material properties change as a result of heating or cooling.
After explanation, the students should be able to explain that observed material property changes are due to changes on microscopic level of materials.
Students should be able to explain that atoms and molecules increase/decrease their relative mobility when heated or cooled respectively.
Engage
The lesson begins with a fairly straightforward engage. The students are asked to think about materials on smaller and smaller length scales. An example of how this would go would be that the students will be asked about a basketball, then they would think about the bumps on surface, then they would be asked about the surface of those bumps, and ultimately to think about the material the rubber is made of.
The lesson is made up of a collection of demonstrations and experiments. Each one has its own explore-explain-elaborate arc. This basic engage gets the students thinking about the building blocks of materials that they see every day. This will help them visualize atoms or molecules that make up a material that they can use as a reference when doing subsequent demonstrations.
The instructor can use a PowerPoint or white board to have images of a material with greater and greater magnification to help students in this exercise. The PowerPoint used in this lesson can be found on the University of Southern Mississippi (USM) NSF GK-12 website (http://www.usmgk12.org) and used as an example.
5 mins
Explore
Nitinol Memory Wire Demo Materials needed: Nitinol “memory wire” (ordered from Educational Innovations), heat gun
Wire is deformed and then heated by the students. The heating returns the wire to its un-deformed state. Students are then asked what the heating is doing to the material, and how they think it is being done. Students give hypotheses of what is going on and then defend their thoughts.
A detailed description of Nitinol and how shape memory materials work can be found at:
http://en.wikipedia.org/wiki/Nickel_titanium
http://en.wikipedia.org/wiki/Shape-memory_alloy
15 mins
Heating an Iron Wire Experiment Materials needed: Iron wire, Variac connected to wire, magnet, ring stands, mass (50-200g)
This “Explore” heavily focuses on students’ observations, inquiries, and hypotheses. An iron wire is pulled taut and has each end attached to a variable electrical source. Before heating a mass is hung on the middle of the wire. A single magnet is also attached somewhere on the wire. The current through the wire is slowly increased and students observe and call out what is happening. They must also explain why the think the action they are witnessing is occurring. The wire slowly begins to dip and as the current is increased and the wire gets hotter the wire begins to glow bright orange and then white. The magnet then falls off of the wire giving the students another observation to record and begin to submit explanations for. The current is finally cut off and the students observe the wire rise up as it cools.
A detailed description of the experiment and solid phase changes can be found at:
http://stem2.org/je/hotwireppt.pdf
30 mins
Milk Jug Demo Materials needed: empty milk or water jug, heat gun
A normal milk jug is shown to the students, and they are again asked to record observation with special emphasis placed on optical properties. A discussion can be had with the students about what they know about why light may not come through the wall of the jug directly. The side of the jug is then heated with the heat gun. The wall softens and also turns translucent. This being the third demonstration students should be able to begin to give explanations before the “Explain” portion relating to the movement of the polymer chains to describe the phenomenon observed.
A detailed description of the demonstration and the phenomenon observed can be found at: http://www.asmfoundation.org/content/docs/intropoly.pdf
10 mins
Polystyrene Cup Demo Materials needed: polystyrene plastic cups (not Styrofoam), heat gun, tongue depressor
This demonstration is about shape memory in polymers similar to that seen in the Nitinol demo earlier. A discussion should be had with the students about the process of shape memory seen previously. The cups are heated with heat guns and held down (so they don’t fly away) with the tongue depressors. The plastic’s shape returns to a sheet that it was originally molded from. Students are asked to describe how the cup ids able to do this. At this point in the lesson the students should be able to provide good explanations including the mobility of the polymer chains.
10 mins
Happy/Sad Balls Materials needed: Happy/Sad Balls demonstration kit (from Educational Innovations), tongs, liquid nitrogen
Two balls of similar appearance are passed around. Students are asked which will bounce better and then a drop test is performed. Students are asked for their explanations of the balls behavior. The balls are then placed in liquid nitrogen (-170oC) and dropped again. A difference in properties is then observed and students should able able to relate that to the mobility of the material. The concept of glass transition temperature and its relation to molecular mobility can also be introduced with this demonstration.
A full description of the experiment and what is causing the phenomenon can be found at: http://www.evilmadscientist.com/2006/happy-and-sad-balls/
30 mins
Heat Treating Steel Materials needed: 4 steel hair pins per students, tongs, propane torch
Students heat treat steel hair pins in 3 different ways (anneal, quench, and temper) the student then perform bend to break tests on each and record the results. The students compare their results with each other and make suggestions as to what is happening in the material that leads to what is seen.
Students will have 4 sample hair pins (Annealed, Quenched, Tempered, and Control)
Annealed: Students heat the bend of a hair pin to red hot with a propane torch and then allow the pin to air cool back to room temp.
Quenched: Students heat the bend of a hair pin to red hot with a propane torch and then quickly dunk the pin into cool water.
Tempered: Students heat the bend of a hair pin to red hot with a propane torch and then quickly dunk the pin into cool water as in the quenched sample but then the hair pin is placed into the flame again for a few seconds (do not let get red hot).
Control: Unheated hair pin.
A detailed description of the experiment and what heat treatment does to steel can be found at: http://www.asminternational.org/content/docs/heattreatingsteel.pdf http://www.youtube.com/watch?v=98lh5Q0M0cg
60 mins
Prince Rupert’s Drops Materials needed: Glass rods, propane torch, large beaker filled with water
The tip of a glass rod is held over a propane torch. The tip is held over a large beaker filled with cool water. The glass in the tip of the rod becomes molten and eventually flows and drops into the beaker, where it rapidly cools and solidifies into the shape of a tear drop. Continue this process to produce as many Prince Rupert’s Drops as desired. This demonstration follows the same theme of molecular mobility. The Prince Rupert Drop is an example of tempered glass. It becomes very hard and will not break when struck firmly with a hammer, but will shatter into a fine powder if a crack propagates past the surface into the sample. Such crack can be propagated in the Prince Rupert Drop easily by snapping the thin tail of the drop. This can be coupled with the hair pin experiment to exemplify drastic property changes that can be imparted on a material by heat treating in different ways.
A full description of the experiment can be found at:
http://www.popsci.com/diy/article/2008-06/shattering-strongest-glass
http://en.wikipedia.org/wiki/Prince_Rupert's_Drop
http://www.youtube.com/watch?v=Pdy2_vi0FfM
45 mins
Explain
After every demonstration or experiment described in the explore section the class is called back to the board where a 5-15 minute lecture is given to describe in further detail the specific phenomena observed. The instructor can use a mixture of PowerPoint slides and videos to keep the students attention, and not have the explain phase seem monotonous. The PowerPoint used in this lesson can be found on the USM NSF GK-12 website (http://www.usmgk12.org) and used as an example.
5-15 mins per demonstration
Elaborate
Due to the nature of this lesson (multiple demos and experiments with a common theme) the students are learning what explains the phenomenon they observe. The students then go into another demonstration or experiment serving as an elaboration of the main lesson which furthers their understanding of the main idea of the lesson that heating a material allows for the atoms or molecules of the material to have increased mobility. As the lesson progresses each new explore activity is marked with more complete and accurate descriptions of what is happening in materials from the students.
Takes place throughout lesson
Evaluate
The students are given work sheets to work along with the lesson and each demonstration and lesson. The worksheet has a blend of direct questions (such as “what happened when X was heated?”), and more open ended explanation questions for students to apply their own understanding to explain what they are observing.
Work sheets are collected and graded. A summary paper can also be assigned to the students to further assess comprehension of the lesson.
Takes place throughout lesson.
The worksheets used in this lesson can be found on the USM NSF GK-12 website (http://www.usmgk12.org).
Safety:
This lesson includes extreme heat and cold. Students should be made aware of dangers involved should an accident occur with the hot or cold materials. Students should wear lab goggles and gloves at all times and if possible they should also wear protective outerwear such as a lab coat or apron. Considerations for specific demos/experiments in this lesson are given below.
Iron Wire Experiment: the teacher should be the only person running the vairac and the students should be far from the wire as the experiment runs. The weight and magnet will also be hot so do not allow the students to touch them until cooled and the magnet should bit be over anything that can easily catch fire for when it falls.
Happy/Sad Ball Demo: This demo utilizes liquid nitrogen (-196 0C). Students should be instructed not to touch the LN2 to prevent cold burns and also to not touch anything taken out of the LN2 before letting it warm up. The balls placed in the LN2 should be handled with tongs.
Heat Treating Steel: A propane torch with an open flame is sued in this experiment. All heat treated samples should be handled with tongs. Students should not have any loose-fitting or dangling clothing. Teacher or supervisors are to be the only ones operating the propane torch. “Annealed” samples should be allowed to air cool fully before placing down to avoid burning table surface.
Prince Rupert’s Drops: A propane torch with an open flame is sued in this experiment. Students should not have any loose-fitting or dangling clothing. Teacher or supervisors are to be the only ones operating the propane torch. Water beaker should be large enough to allow for a big target for the molten glass to fall into. Nobody should attempt to retrieve the glass drops from the beaker until the propane torch is turned off.