ingridscience

Remove the backing from the contact paper and tape it, sticky side up, to the table in front of a student.
Students stick hexagons of tissue paper to the contact paper, arranged as a honeycomb (or not). Tell them that once the tissue paper touches the contact paper it is impossible to get up again without tearing it.

It can be hung in a window as "stained-glass" art.

Distribute a jar of water and a couple of pieces of pottery to each pair or small group of students.
Explain that they will mimic the way that flowing rivers and the rain interact with the rocks on mountains.

Ask students to add their pottery pieces to their jar and screw on the cap. The pottery pieces are rocks.
Ask students to vigorously shake the jar. They are mimicking water and wind bashing the rocks, and wearing them away - the process of weathering. With the pottery, the pieces are broken into smaller particles much much faster than most of the natural weathering of the harder rocks of mountains.

Students look inside their jar to see that they have made smaller particles from their rock, then draw what they see. The left side of the second page of either attached worksheet can be used.

Explain that as rocks are worm away, they make sand and mud particles. Sand particles are larger and mud particles are smaller. The particles are washed into streams, then rivers, then the ocean. In the ocean they are carried by the currents until they are deposited in a calm shallow bay. Over a long time, a sand and mud beach is made, and continues to be built upon.

Optional: compare chalk and granite gravel. Do they break apart more quickly or slowly than the pottery.

Show the students a photo of a bridge or other man-made structure. Point out the shapes made by the steel girders (e.g. triangles in the Burrard Street Bridge, diamonds and rectangles in the Port Mann Bridge). Explain that the shapes are made during construction to make the structure as strong as possible. Tell the students they will be testing different shapes for their strength.

Show the students how to make a triangle and a square from a sheet of paper and tape, how to lay a platform between two identical shapes, and add a load to the platform. Do not reveal what will happen.

Students make two identical triangles and two identical squares by folding a letter sized sheet of paper and taping it closed with pieces of masking tape. If there is time, they can also make two of another shape that they choose (e.g. circle, pentagon). This requires some skill to accurately assess where to make the folds, and to tape the edges together so that there is no overlap. If the students are unable to do this accurately, the teacher should do it for them.
Students test the strength of each shape by laying a cardboard platform between two of the same shape, adding a small container to the centre of the bridge, then adding pennies to the container until the shape starts to collapse or distort.
Students record the number of pennies added to a shape before it distorts or collapses. (See the attached worksheet).

As a class, add all results to a class graph, with number of pennies up the side of the graph and the shapes along the bottom, and find out which shape is the strongest. It is expected that the triangle would be the strongest (see image for one class' results).

(This graph is a good opportunity to show students that sometimes data is a little messy, and one might need a lot of data points before seeing a pattern emerging.
From one group’s results, it might not have been clear which shape was the strongest, but when everyone’s results are graphed together, a pattern emerges: the triangle is clearly stronger than the other shapes. There is not enough data here to determine if the square or circle is stronger.)

Explain why the triangle is the strongest shape: the sides of a triangle are a fixed length, so as a force is applied the angles of the triangle cannot change, so maintaining the triangle’s shape. A triangle will fail when either the sides buckle (as probably happened in this experiment), or when the joints break apart. When a load pushes down on the triangle, the two top sides are under compression as the force from above pushes down on them. The bottom side is under tension as the ends are pulled apart. (So in construction the bottom side that only experiences tension can be made of a lighter material than the upper two sides that must be more rigid to stand up to compressive forces). In the case of the square, the angles can change even when the length of the sides stays the same - it is easily pushed into a diamond shape.

Ask the students to sled down the mini hill on their plastic sleds to make the run smooth. Describe and practice walking up the side of the hill to get back to the top without walking up the area they are sledding on.

Distribute squares of other sledding materials. Ask the students if they think they will sled down on each material faster or slower than on their plastic sled.
Students sled down the hill multiple times, to get an accurate impression of whether the provided material is faster or slower than the sled. They many want or need to do the run on their sled again to compare.
Students exchange sledding materials until they have all tried all kinds.
Students can record results on the suggested worksheet, though we reviewed from our memories to avoid the complexities of writing in the snow.

Sit as a group in the snow, and material by material hear the results the students found, then look at the material and discuss why it is faster/slower than their sled.
Common results (though if your cloth type is different, your results may be different - then discuss according to your results):
The rough felt-like cloth should barely move at all. It has a very bumpy surface which gets caught up in the snow, generating a lot of friction (the surfaces get stuck in each other and stop them from moving past each other so easily).
The smooth fake-leather cloth will move a little, but not as fast as the sled. It has more ridges on it than the sled, which get stuck on the snow, generating some friction which slows it down.
Snow pants vary a lot as they are not so rigid. In interpreting results, you might want to discuss the folds in the pants, the smooth material that they are made of, the bumps of the seams in the cloth - in general more bumpy (little or large bumps in the cloth) slow things down i.e. make more friction.
Some magic carpet sleds have a rough and a smooth side. Students should be able to predict which side will go faster, then can test this out when they return to the main hill.