With our mortar mixtures all dried it was time to test the strength of our walls.  Did we make a good choice with our mortar mixture?  We wanted our walls to be strong enough to keep the bunny out of our garden!

Each pair of first graders tested the strength of their walls by using a wrecking ball.  The higher the wrecking ball was released from, the more force that was used against the wall.  The whole class recorded which angle the wall last stood with.   Each pair's hope was that their wall could withstand the force behind the largest angle with the most force!  As engineers we built our walls and as scientists we tested them.  

First graders first thought about the rocks they brought in to build their walls.  Some rocks were different colors, shapes, and sizes.  Each of these factors would affect the structure of their walls they designed.  We practiced classifying the rocks into different groups.

Then, with their rocks and mortar mixtures in hand, first graders were eager to begin designing their walls.  Spreading their mortar mixture atop and around the rocks they collected, walls were being erected left and right.

Thanks to everyone  who collected rocks!  We had many different shapes, sizes, colors, and textures, just like Yi Min found for her wall.  

First graders are making mixtures of their own and comparing one mixture to the next with graphs.  These mixtures were all made with man-made materials.  Next steps...mixtures with earth materials!!!

If NONE of the mortars passed all three tests, what should we do to design our mortar?  First graders came up with these four suggestions:

1.  Find a new earth material that will pass all the tests.
2.  Add glue to the mortar.
3.  Add more water to the mortar.
4.  Mix the mortars together.

After a long discussion about each suggestion, first graders came up with the following:

1.  Finding a new earth material would mean a lot of digging.  We can't do that!  We're in first grade!
2.  Adding glue to the mortar might make us sick...the wall is going near the vegetable garden and we don't want to take that risk.
3.  Adding more water to the mortar would just make the mortar more runny.  It reminded someone of what happens to sand castles at the beach when the tide comes in.
4.  Mixing the mortars sounded like a feasible idea.  We've already got the mortars, and mixing materials together to make a new material is TOTALLY something a materials engineer would do!

So today we spent practicing making combinations of possible mixtures....dessert style!  

"But Mrs. Brinza.  We only tested the soil, sand, and clay when they were dry and wet.  We didn't see what happened to them once the mortar dried, like in a real wall."

"So what tests should we do?"

Our discussion turned into developing three tests--a sandwich test, a wall test, and an earthquake test.  We gathered more evidence to support which mortar would be the best choice for our walls.  Check out the evidence we gathered from our tests!

When students determined that the dry earth materials were not sticky, they figured out we better come up with a better solution for the mortar for our walls.  A mixture!

By mixing clay, soil, and sand with water, students quickly discovered that it changed the properties of the mixture.  Each mixture not only changed color but also its stickiness.  

Clay was by FAR the "best" choice for a mortar...students had a hard time getting their fingers unstuck.  "We NEED to use this for the mortar!" a first grader shouted.

Currently, we are observing three different dry earth materials--clay, sand, and soil.  We are seeing how large the particles are, if the particles are the same size, and how sticky each material is.  These tests are important as students get ready to make their own mortar to create and test a wall's strength.  

Next step...testing the strength and stickiness of these earth materials when we mix them with water!

Like all engineers, materials engineers are creative.  Materials engineers not only design new materials, but they find ways to use different materials for the same purpose.  Ultimately, they are also able to evaluate their choices and decide which material is the best for a given purpose.  

First graders explored using cloth, brick, straw, and paper for a variety of purposes...and they were certainly creative in their decision making!

Yi Min is an aspiring gardener who quickly discovers that she has competition for eating her delicious vegetables--a bunny rabbit!  After sitting out long hours trying to scare away the bunny, she realizes she needs a better solution to keep the bunny out of her garden.  With a field trip to the Great Wall of China, she is inspired to build her own wall for her garden.  Knowing that natural materials will be easier to find and cheaper than purchasing materials, Yi Min experiments with various earth materials to build a wall.  She works to improve the mortar that will hold her wall together.  By using the engineering design process, she is able to build a wall that withstands the test of time.  Her garden is saved and the bunny must look elsewhere to find food!

Key Vocabulary:  materials engineer, materials, natural, human-made, properties, mixture, mortar, engineering design process.