Update from Ms. Paige:
5th grade - Mr. Calubaquib
In Mr. Calubaquib’s class, we were examining how much salt can be dissolved in 50mL of water. We tested this by adding a 5mL spoon of salt to a bottle containing 50 mL of water. We would shake the bottle for 1 minute and then observe if the salt dissolved. We know that a solution is a type of mixture in which a solute (in our case salt) dissolves in a solvent (in our case water). Solutions appear clear. We slowly added spoons of salt until we observed undissolved salt on the bottom of the bottle. We had definitely made a saturated solution. A saturated solution is a solution in which no more solute can be dissolved in the solvent. But the challenge was to find out how much salt could dissolve in the 50mL of water. We only knew approximate spoons, and even then, not all of that salt was dissolved. We ran out of class time the first day, and picked up here the next week.
We realized that we could filter the saturated salt solution. We knew that the salt that is dissolved cannot be removed by filtration. Therefore, only the dissolved salt will pass through the coffee filter, leaving behind any undissolved salt on the filter. Then we could weigh the saturated salt solution relative to 50mL of water. We added gram weights to the water until the two cups were in balance. The gram weights were equal to the amount of dissolved salt. If I recall correctly, most students got 9-12g of salt that dissolved in 50mL of water.
I then went on to demo the concept of supersaturation by making rock candy. I first made a saturated solution of sugar and water. The students directed me to make a saturated sugar/water solution by adding sugar to the water until I no longer saw it dissolving, approximately 1 1/2 cups of sugar to 2 cups of water. Then in a second pan, I made a saturated sugar/water solution, but at 100oC (boiling water). I stirred water on a burner until it was boiling, and then I added sugar until it stopped dissolving. This was approximately 6 cups of sugar in 2 cups of water. I emphasized that the hot solution is still just supersaturated. The hot water contains the exact amount of sugar that will dissolve at that temperature. However, once we turned the heat off and it started to cool, the water would contain much more sugar than should be dissolved at room temperature. When a solution contains more solute than would normally dissolve in the solvent, we say the solution is supersaturated. Supersaturation is a precarious situation because the solute does not want to be dissolved in the solvent. By adding a surface for the solute to crystallize on, the solute will come our of solution. We added a skewer to both the saturated and supersaturated solutions. Within 2 days, we saw beautiful rock candy crystals of sugar on the skewer in the supersaturated solution but not in the saturated solution. We again reiterated that the sugar did not crystallize out of the saturated solution because that solution had the amount of solute dissolved in the solvent that it can accommodate.
This last week, we started looking at chemical reactions. I showed students that calcium chloride, citric acid, and baking soda will all individually form solutions with water. The question was, “What will happen if we mix two of the solids together with water.” We tried each combination and observed what happened. Calcium chloride, baking soda, and water fizzed, and then produced a white precipitate (a solid that forms during a chemical reaction). Citric acid, calcium chloride and water formed a solution. Citric acid, baking soda and water fizzed, but then formed a solution. We realized that the fizzing was due to a gas, but we hadn’t added a gas to the cup. This was a clue that something different had happened. We had seen a chemical reaction. In a chemical reaction, the atoms of the substances are rearranged to form new products. Production of a precipitate, gas, temperature change, and color change are all signs that a chemical reaction has happened.
5th grade - Mr. Ellingson
Mr. Ellingson’s class started three weeks ago on the chemical reaction experiment described above. We have since gone on to look at chemical reactions in greater depth. We have learned the chemical formulas for many of the substances we have been using (baking soda is NaHCO3, water is H2O, carbon dioxide is CO2, calcium chloride is CaCl2, and salt is NaCl). Chemical formulas are like a shorthand way of writing what atoms are in a compound and how many of each type of atom are present in a molecule (a single particle of the substance). We also talked about how we represent chemical reactions in using chemical equations. We put the reactants on the left side of the equation. These are the substances that we have at the beginning of the reaction. We then draw an arrow depicting that the substances are changing into something new. Then we write the formulas for the products on the right side of the arrow. The products are the new substances that are formed in a chemical reaction. We learned that in a chemical reaction matter cannot be created or destroyed, so all of the atoms present in the reactants must be present in the products. The formulas have to be balanced.
We spent a week looking at balancing chemical equations. We used M&M’s to represent atoms. We placed a colored M&M for each atom of a reactant. We then rearranged these atoms and moved them to the product side to show that all the atoms have to move to the product molecules; not M&M’s can be left behind or created. Once we successfully rearranged our atoms to make the products of the reaction, we got to eat them! Always a highlight!
Then this past week we let students make their own hypotheses about what will happen when different chemicals are mixed and try out their experiments. Each group of 2 students was allowed to pick 2 solids and 1 liquid from materials available (calcium chloride, baking soda, salt, citric acid, vinegar and water). They wrote a hypothesis about what they thought would happen based on their previous experiences, and then they put their materials in a bag and saw what happened. Some bags puffed up due to production of carbon dioxide. Other bags formed a precipitate or a solution. Some bags changed temperature. Students wrote about their observations using the vocabulary we have been learning in this unit.
4th grade and Mr. Briggs 4/5 split
We have been exploring the properties of minerals. Minerals are pure earth solids; they are the building blocks of rocks. We had previously seen that we can differentiate minerals based on the properties of color, texture, crystal structure, and luster. Three weeks ago, we learned about the property of hardness. Hardness is the resistance of a material to being scratched. The Mohs Scale is used to describe hardness. This is a scale from 1 (softest, talc) to 10 (hardest, diamond). In geology, minerals are tested for hardness using the scratch test. The scratch test consists of trying to scratch a mineral with a fingernail, aluminum object and stainless steel object. Based on which tools scratch the mineral, the geologist can assign a hardness score to the mineral. We practiced the scratch test using 4 unknown minerals we had been observing. Based on our results, we were able to identify the minerals using hints like quartz is the hardest mineral and gypsum is the softest. We were able to see how mineral hardness is a very useful property for identifying minerals.
Next, we looked at 4 rocks. Rocks are solid earth substances consisting of 2 or more minerals. We looked at basalt, limestone, marble, and sandstone. We first studied these rocks for evidence that they were rocks. We saw that marble had flecks of high luster in a background of low luster. We thought this was evidence of at least 2 minerals being present. Sandstone had particulates of brown, black and tan. We thought this was evidence of 2 or more minerals of different colors. We then learned about an interesting property of one of the minerals we had been studying - calcite. Calcite has a chemical property that when it is mixed with acid, it fizzes. We put a sample of calcite in a vial of vinegar and saw effervescent bubbles. I then asked how could students find out if any of the rocks contained the mineral calcite. Students realized that if they put their rock samples in vinegar, they should see fizzing of rocks containing calcite. One by one, we put the rocks in vials of vinegar and looked for fizzing. It was clear that basalt does not fizz and limestone fizzes. Marble and sandstone were more difficult to decide about. We decided we needed more evidence.
This last week, we talked about how to get more evidence. I pointed out that mixing calcite with vinegar produced a gas (the fizzing), but it might have produced another product. How could we see if there was another product. Students had lots of great ideas. They suggested we could look for a new solid in the bottom of the vial, or we could use a high power microscope to examine the vinegar closely. As we don’t have a microscope, and we didn’t see a solid, I asked what they could do if something was dissolved in the vinegar like salt is dissolved in saltwater. Students suggested we could evaporate the vinegar and see if anything was left. I had done this the week before to give the samples plenty of time to evaporate. We looked at the evaporation dishes and compared them to our calcite + vinegar dish (positive control; what we expect to see if calcite is present) and to a vinegar alone dish (negative control; what we expect to see if there was no calcite present). By comparing each rock’s evaporation dish to the two controls, we could determine if the rock contained calcite. We observed that after calcite reacts with vinegar there is a white crystal in the evaporation dish. We saw these same crystals in the limestone and marble dishes, but not the basalt and sandstone dishes. Based on our two sets of data (fizzing and evaporation dishes), we concluded that limestone and marble contain calcite.
3rd grade - Ms. Lin
We finished up our studies on energy a few weeks ago by looking at how energy is transferred from one place to another. We had explored energy transfer in 5 different systems. We found that energy moved using waves (sound to make rice dance, water waves to move a ping pong ball, and mechanical waves in a spring bouncing back and forth), wires (battery to make a motor shaft turn), and objects (bowling ball to knock down pins). We took a week to process all this information and put it together. We did some reading from the text book, rehashed our explorations using images on the bulletin board to describe what we had seen, and took a quiz.
Next, we started exploring one particular kind of energy - light. We talked about how we can only see when light hits on eyes. That’s why we can’t see anything at night; there is no light to hit our eyes. We also learned the science word for light. We call the energy coming out of a light source - light rays. We learned that light rays only move in straight lines. We talked about how when light hits an object a few different things can happen. The light can be transmitted. This means the light passes through the object. This happens if the object is transparent or translucent. An example of this is light rays from teh sun passing through our classroom window into our classroom. Light can also be reflected when it hits an object. This means that the light bounces off the object in a new direction. An example of this is light hitting a mirror and bouncing off. To explore reflection more, we used a flashlight and mirrors to complete challenge questions. We had questions like, “Can you make the flashlight light rays shine on the side of the flashlight?” or, “Can you make it appear the flashlight light rays appear to go through a book?” Students worked in pairs positioning mirrors. Once they completed the challenge, they drew a diagram in their notebook of the mirror positions and the light rays’ path.
This past week, we reviewed what we had done with the flashlight. We used white string to trace the path of a laser pointers light rays as they bounced off several mirrors and ended up on me. We saw that the light traveled in a straight line, when it hit a mirror it reflected (bounced in a new direction), and then continued in a straight line. We then used the white string to map how I was seeing the student sitting to my right. We worked backwards. We knew the light ended at my eye, traced back to the light rays reflecting off the student, and then traced further back that the light had begun at the overhead light. We tried an even more difficult scenario as a class. I acted the part of a parent driving, a student was the rearview mirror, and 2 students played George and Harold (of Captain Underpants fame) poking each other in the backseat. We used the white string again to trace how I saw the kids in the backseat given I don’t really have eyes in the back of my head:)
After reviewing reflection and light rays traveling in straight lines, I introduced that light is made of all colors (ROY G. BIV; red, orange, yellow, green, blue, indigo, violet). I exchanged my white string for a set of red, orange, yellow, green, blue, indigo and violet strings gathered together. We then did experiments to verify what I said. We used a prism to break sunlight into a rainbow. Then I gave students a diffraction grating (a little slide-like viewer that breaks light into the different wavelengths that make it up). Students viewed the overhead lights, sunlight, and flashlights using the diffraction grating. They saw that they observed all the colors of the rainbow. We then used the diffraction gratings to view a flashlight covered with a red plastic film or blue plastic film. Students saw that when the light was covered with a red plastic film, they only saw red, orange and yellow through the diffraction grating. When students viewed the flashlight covered in blue plastic film, they only saw blue, purple, indigo and green through the diffraction grating. We thought about why this might be. We knew that the flashlight was producing all the colors of the rainbow as we had seen initially, but after going through the film, some of the colors were missing. I told them that these colors had been absorbed (taken in by the film and converted to heat energy). This is one more thing that can happen when light hits an object. In the case of the red film, the film absorbed the blue, indigo, violet, and green colors. In the case of the blue film, the film absorbed the red, orange, and yellow colors.
We ended by thinking about how we see color. A student with a blue shirt stood beside me. We knew that the white light from the overhead light is made of all colors. We used by multi-colored string to model this light coming from the light and hitting the student’s blue shirt. We also knew that we saw blue. We realized that this must mean that only the blue light hit our eyes, and the rest of the colors must have been absorbed by the shirt. Next, we modeled what happened with a student wearing a black shirt. Again, the multi-colored light must hit the shirt, but our eyes don’t see any of the rainbow colors. Just like at night when we see black, this must mean that no light is hitting our eyes after reflecting from the shirt. The shirt is absorbing all the colors. This is why black shirts get so hot outside; they absorb all light and convert it to heat. Last, we modeled what happens when light hit a student’s white shirt. The multi-colored white light hits the shirt, and we realized that because we see white, it must mean that all the light is being reflected.