ingridscience

Students get out their lunch bags and open them up. They look at the containers and the bag itself, to find insulating/reflective materials, which slow down heat movement.
Heat always moves from a hotter object to a cooler object. Lunch bags and food containers are designed to either keep heat in food that needs to stay warm, or away from foods that need to stay cool.
Students draw their lunch bag, and the insulators they found, optionally on the “Lunch bag insulation” worksheet (attached below).

Examples:
Anything padded or thick plastic (lunch bag itself, plastic containers, thick wrapping) does not transfer heat well, so will block heat from getting into food that needs to stay cold, or keep heat in food that needs to stay warm.
Metal soup containers and thermos flasks have a layer of air between two walls. Air does not conduct heat so well, so slows down heat leaving the container.
Silver-lined bags reflect heat (by a heat transfer process called “radiation”), so keep heat inside a container, or keep heat away from things that need to stay cool.

This activity still in prototyping stage.

Best method so far is to use hot water to melt ice cubes, which are nested in different materials.
Photos show how to make a nest, with a piece of tin foil and an optional inset of cloth/plastic. The nests are pushed into a ramekin (or other small bowl with a flat base) to shape them. Add ice cubes of the exact same size to each nest, and float the nests in a tub of just-boiled water.
Students record which ice cube melts first, second etc. But nests often leak or tip over, in which case that nest is excluded from a group's results.
In all groups, the ice cube in the foil nest melts first. Then the ice cube in a plastic sheet, then tissue paper, thin cloth, thick cloth, and lastly bubble wrap.
To adapt the method, somehow clip/tape the nests to the side of the tub so they don't fall over.
Discussion: The heat energy in the air is transferred to the ice and heats it up and melts it, by conduction. The cloth/thick plastic does not conduct heat well, so slows down how rapidly the ice melts. Tin foil is a metal and is a good conductor - it transfers the heat energy rapidly to the ice, so the ice melts fastest when in a nest made of only tin foil.

Previous experimental method (see last three photos):
Each student group is given ice cubes to wrap in different kinds of cloth (fur, thin cloth, or no cloth).
https://www.acs.org/content/dam/acsorg/education/resources/k-8/science-…
Problems: It takes a long time to completely melt the ice cubes (an hour or more), and the ice cubes must start out exactly the same size to be able to compare their final sizes. Other variables are how quickly the students wrap each ice cube and how hot the classroom is.

Space the metal rods out around the circle of students, and ask the students to touch a metal rod and feel how warm it is. (You may need to ask them not to hold them as warmth from their hand heats up the rod.)
Gather up the rods, briefly dip them in the kettle of recently boiled hot water, then lay out again. Ask the students to briefly (copper metal heats up very fast) touch the end that was in the water.
Students may also explore and feel the end of the rod that was not in the water, and the centre of the rod, and notice differences along the rod. They may also notice that after a short while, the whole rod will cool down again.
Discuss what is happening in terms of heat:
The molecules of water moved around faster as they were heated up. (Simulation of molecule movement in a liquid as it is heated: http://www.middleschoolchemistry.com/multimedia/chapter1/lesson2.) These faster moving water molecules transfer energy to the metal rod where they are touching. The energy from the hot water makes the molecules of the metal rod move faster, which we can feel as the rod heating up. The heat spreads up the rod as the faster molecules at the end of the rod bump into adjacent molecules and give them energy too - so the middle of the rod (even though it was not touching the water) got warmer as well. Eventually the molecules lose their heat energy to the air and the rod cools down again.
The movement of heat when molecules transfer energy between each other by colliding with each other is called “conduction”.

Tell the students that they will be building a structure large enough for at least one student to get into (and might fit more). Their structure, however, will only be made from newspaper and tape, and must stand up on its own.
Prepare students by letting them know that this project will take some time and requires some patience. During the first lesson the class will be starting to make many rods from the newspapers. In a later lesson, when there are enough rods, they can be fastened together to make the structures.

Rod preparation:
Show students how to make newspaper rods:
Make a stack of eight sheets of newspaper and roll them tightly around the plastic/wooden rod. (Photo 1.) Use three small pieces of masking tape to secure the ends and centre of the newspaper so that it forms a rod. Remove the plastic/wooden rod from inside the newspaper roll.
The newspaper can be rolled along the length of the newspaper as shown in the photo at right, although wider newspaper which produces longer rods is preferable for building large structures more quickly.
Spend some class time making a common bin of rods. Store the rods upright so that they do not get bent. Make sure that the rods made are tight and stiff.
The students will continue to add to the common bin of rods throughout the following days, when they have time. The class needs about 50 rods for each group of four students.

Show students how to tightly join the newspaper rods:
Flatten the ends of two newspaper rods. Hold the flat faces tightly together and bind them tightly with masking tape, to make a strong and flexible joint (see photo 2)
Two students working on a joint together will allow the strongest joints to be made, as some hand strength and coordination is needed.
Often during the Big Build, additional rods will be added to the joint. The end of these additional rods should also be flattened and added to the stack of flat rod-ends, then taped tightly.
Students should be reminded throughout the Big Build to make their joints in this manner. As more weight is added to their structure, weak joints will not support the load. Strong individual joints will ensure success of their larger structure as they build it.

Introduce strong shapes that can be used for the Big Build:
Depending on whether students are already familiar with the superior strength of a triangle in structures, review or introduce this concept.
Ask students to build a triangle from three newspaper rods, assembling the joints as demonstrated above. See photo 3. Ask them to feel how strong the triangle is. If there is weakness, point out the most likely source: a joint that is not flat and bound tightly with tape. Check and assist in the students’ work to ensure strong, flat joints.

Once students are confident in joining rods together and in building strong triangles, let the Big Build begin!
Allow a morning (or longer) for students to work on their structures. Assist where needed, but make sure the students are designing and building their own structures as much as possible. Groups can borrow ideas from each other. Once the frame is in place, students may want to add a skin of a single sheet of newspaper.

Tell students that they will be working in groups (of 2,3 or max 4) to build a long bridge between two chairs/a chair and desk, using the materials provided. The bridge can be as narrow as they wish (it can be for ants to cross on), but it must stay up off the ground. If you would rather not have the competitive nature of this challenge, make a scenario, such as "we will turn our classroom into a city with long bridges for ants to move between desks and chairs".
Students may only use the materials provided, and cannot get any additions/replacements. Materials can be opened up, torn or broken if the students wish.
Tell them to investigate and manipulate the materials to see their different properties and ways that they might be used. Some materials will be good for structural pieces, some will be good for fastening those pieces together, some could be used as either.

Hand out bags/trays of materials, or ask students to collect their own tray of materials from bins.
Allow 20 minutes or more for building.
Some creative ideas I have seen (pictured), usually overcoming the little amount of tape they are given (try the challenge with no tape??):
Using small pieces of pipe cleaner, or toothpicks or pieces of chopstick to attach pieces of paper together.
Opening the clothes peg wide so that it clamps onto a table edge, as well as to a piece of paper.
One end of the bridge simply sitting on a desk, using materials to keep it weighed down.

Part way through building, visit each others' bridges and ask each group present a challenge they encountered and how they overcame it, or to ask the rest of the class to help them solve it. Just as engineers share ideas to solve structural problems, students are encouraged to share ideas within and between groups.

Discussion points to bring up during sharing:
Each of the materials have different properties - some are flexible, some are strong (metals are strong and flexible, paper is light). Some can be broken apart to make them longer.
Doubling up of materials makes them stronger. This is also done in making real bridges e.g. several steel beams are strapped together to make a support.
A bridge needs two components: 1. structural pieces, which make up the scaffolding and give a bridge its length. Students may have used chopsticks, extended pipe cleaners or long pieces of paper, while the structural elements in real bridges are steel or wooden beams that are long and rigid. 2. fasteners hold the the structural elements together. Students might use bolting (e.g. weaving a toothpick through two pieces of paper), taping, or crimping (e.g. tightly wrapping a piece of pipcleaner around a chopstick or using a clothespin) - all these methods are used to make real bridges. Other methods used to fasten real bridge structures together are welding, gluing and cement. Some of the materials given to the students can only be used as structural pieces, some only as fasteners, and some as both. The students will find unanticipated ways of using the materials.

After the lesson is completed, optionally have students remake the kit bags for the next use of them.

Show students an image of a local bridge with a visible frame, and ask if they have seen or been over this bridge, or one like it. Tell them that the frame is strong and keeps the bridge rigid, even with the force of all the cars and trucks driving over it.
Show students an image of a frame of a house, and ask if they have seen anything like this on a construction site in their neighborhood. Tell them that behind the walls and under the roof of every building there is a frame like this one that supports the weight of the building and everything in it.
Point out the steel/wooden beams that make up the frame of the bridge/house. Tell students that these beams are fastened together in shapes that are strong, which can distribute and balance the forces on the structures, so that they do not fall down.
Explain to the students that they will be building their own regular polygons, from rods and fasteners, and testing them for strength, to find out which shapes are the sturdiest.

Show the students the rods and fasteners that they will work with (the short plastic strips and the brads), and demonstrate how to fasten the plastic strips together to make the outside of a shape (see photo 1), with three or more sides. Then demonstrate how to test the strength of their shape by laying a square on the table and gently pushing it from one side (see photo 2).

Distribute kits containing eight short plastic strips and eight brads to each student pair. Distribute one worksheet (attached below) to each student.
Students are instructed to make a triangle, a square, then any other simple polygons they like. The shapes should be a simple outline of a shape, with no cross bracing. (Students will be able to build up to an eight-sided octahedron with their kit.) Students should draw each shape in a box on their worksheet, name it if they can, and record the number of sides.
After testing it for strength, they also record on their worksheet how strong and sturdy it is compared to their other shapes (for example using a star system). Polygons that hold their shape well (typically the triangle) are recorded as being the most sturdy (e.g. three stars). Polygons that easily distort and lose their shape (most of the other shapes) are recorded as being the least sturdy (e.g. one star).

Students add the shapes they have built to a class chart, with names and number of sides, until all shapes built are listed for all to see.
Students are asked, pair by pair, which shape they built was the most sturdy, and how sturdy the other shapes were. Record the sturdiness next to the appropriate shape on the class chart. (Some students’ data may be different from others, as sometimes the brads are tight enough to restrict the movement of the plastic strips. However all results are valid, as they are what the students observed, and are added to the data. The outlier data points are not the majority so are not included in the discussion of class results.)
Summarize the class chart: the triangle should be the shape that most often has three stars. Other shapes will vary in their rankings, but should usually rank below the triangle.

Discuss why the triangle is the strongest shape: a triangle will hold its shape even when forces are applied to it from any direction. The shape of a triangle can only be changed by changing the length of its sides, so if its sides stay rigid (do not buckle) the triangle is stable. A force on a triangle is spread around the shape, as compression (pushing forces) and tension (pulling forces), and these forces are balanced. In comparison, a force on a square or other shape with more sides can change the shape by collapsing the corners.

Ask students how they might make the weak shapes stronger. If prompting is needed, ask them which was the strongest shape (triangle), then how this shape might be made within the weak shapes.
Distribute five long plastic strips to each student pair at their desks.
Ask students to make their original shapes, then add cross braces to reinforce the weak shapes and make them strong. Photos 3, 4 and 5 show some examples of the many possible outcomes.
Ask students to retest the reinforced shapes for strength, and look for the shapes (usually triangles) that have been made from the original, larger shape.

Students bring one of their reinforced shapes to a group discussion, and show the triangles that are within it. If there is any weakness in a shape still, ask students how this could be strengthened, and point out the additional triangles that are made.

Look again at the images of the bridge and building. Ask students to find the shapes within the frame, noticing that many or all of the shapes are triangles. Engineers have learned that triangles are strong shapes, so build them into any large structure to keep it rigid and strong.

Show students ideas of mobiles.
Ask them to draw their mobile, probably best with just two sticks for time, and more interesting if one stick hangs from another so the balance point is not in the centre (see first photo).

For materials, thicker twines (e.g. hemp) and heavier objects (e.g. pine cones) allow students to do more of the tying themselves.
For hanging origami, embroidery thread can be stapled to the paper.

When they start to build it, students should work up from the bottom of the mobile.
First hang the materials to each end of the bottom stick, then hot glue in place.
Then attach the thread and move it sideways along the stick until this bottom stick is balanced (ask students to predict where the balance point will be if they have done activities on balance points and relative masses already). Then hot glue in place (with as little hot glue as possible so the balance is not upset).
Then attach the top of this thread to one side of the next stick up (or more centrally if the students prefer a more symmetrical mobile). Add (an)other object(s) to the end(s) of the stick. Tye the hanging thread and move it until the balance point is found, before hot-gluing in place.