Unit 4 Reflections: Worksheet 1 and Electrolysis of Water

Going by the modeling "book" is not working for me lately.

Friday: I expected pure substances vs. mixtures to be a review for my students, especially after the feedback I was receiving in our post-lab discussion.  The topics are covered heavily in physical science. The students usually blow right through it in years past.  I thought it would be a great chance to squeeze in some much needed textbook reading/writing practice, with it being a familiar topic that is not all that difficult to grasp from reading.

Um... no.  That's not how it went with these students.

Friday, in class, they were assigned to read the (very short) unit out of the textbook on classification of matter.  They were then to write me a paragraph classifying the stuff we saw in the lab (salt, sand, iron, salt/sand/iron together, water, sulfur, iron, iron sulfide) as a pure substance or a mixture using vocabulary they read in the text.  I figured after they read about the topic, we'd jump right into Worksheet 1 on Monday.

What they actually did instead of reading-- sit with the book in front of them without flipping a page, then turned in a list of garbage that showed they didn't even as much look at the headings on the pages.  Not cool.  I know it was Friday, but COME ON.

So, I got to spend all of Monday reteaching what they didn't read in the book.  I did it in a PowerPoint that I've used in the past, then finally gave them Woksheet 1.

I've never understood why this is so hard for students:

I used to assign a similar worksheet in years past and my students went into panic mode when they saw it.  After my Modeling Workshop, it occurred to me that I was assuming that students had a conceptual picture of particles when it was something I truly never taught.  This year, since we have been explicitly working in conceptual "particle" mode all year, I didn't anticipate it being nearly as panic inducing.  Wrong again.  *head desk*

So we wasted more time today slooooowly correcting the very wrong answers on Worksheet 1 until it finally seemed like my students had some idea of the difference between elements, compounds, and mixtures.

Onward ho-- next we were supposed to start building towards the Law of Definite Proportions with a demonstration using a Hoffman Apparatus.  My Modeling Workshop was generous enough to provide us all with our very own Hoffman Apparatus!  Unfortunately, they didn't give us a power source.  Never fear, they told us, you can just use a 6V or 9V battery.  Ha.  Hahaha.  Ha. Of course, I procrastinated until the last minute to try this idea and found that while a battery will cause some decomposition, I could not get the reaction to go nearly fast enough to be visually impressive.  Maybe it was just me.

I needed a backup plan.  My first thought was to do the 9V battery/pencil lead electrolysis of water-- but a single set up is way too small for an effective demo.  Plus, I really wanted them to see that it was twice as much hydrogen than oxygen, and actually prove it was hydrogen/oxygen and not just bubbles.

Thanks to Google and YouTube, at the 11th hour I was able to rig up some of these setups using materials I had on hand:

Small plastic container with two push pins through the bottom, 2 test tubes, a 9V battery, and a solution of water with a small amount of sodium biocarbonate

The containers were a little cumbersome to manipulate, but the setup worked well overall.  Between weak batteries and time constraints, we didn't see a perfect 2:1 ratio, but the students clearly saw more gas being formed on the cathode side than on the anode side.  I was able to come around with a flaming splint and demonstrate the hydrogen "pop" to each group.  There wasn't quite enough oxygen to re-ignite a hot splint, but it was enough to at least make the flame visually grow.  We discussed how water vapor would not cause a flame to grow or pop-- too much water vapor may even extinguish a flame.  We also discussed that the container did not feel hot enough to be boiling, so it couldn't be "boiling" water.

I told them that scientists have found that a compound of a substance always has the same ratio of elements.  Water is always 2H:1O.  We then hypothesized the ratios of elements in other familiar compounds, like sodium chloride and glucose.

We were going to watch "Gases and How They Combine," as suggested by the lesson plan.  I watched the video myself on YouTube and it is BORING and dated.  While the demonstrations and explanations are great, I don't see my students paying enough attention to get anything out of it.  I think we'll jump right into Worksheet 2 tomorrow... then on to Dalton's Playhouse.

Despite being dreadfully far behind and feeling like 50% of my students are shut down... I do hope that by the time we get to balancing equations, it should be a non-issue.  That's basically all they are doing in Worksheet 2.

Unit 4 Reflections: Separating A Mixture

I've had to shake things up a lot.  Last week, we had two more snow days and two days where I lost my students to standardized testing.  I basically said to heck with the rest of Unit 3.  We didn't do any of the specific heat calculations.  We quizzed on the types of energy, energy bar charts, heating/cooling curves, and phase diagrams (my addition) and called it a loss.

I'm also shaking up Unit 4 a bit.  For starters, it begins with demos and discussion.  Unless I'm blowing something up, my unmotivated, under engaged juniors don't give a darn about demos.  And I've been struggling all year to get my students to buy in to group discussion-- it does not happen easily.  I truly needed to get them in the lab.  I fell back on the old "Separation of a Mixture" lab, an activity that I usually do at the beginning of the year to introduce them to the concept of experimental design and properties and mixtures.

We started Unit 4 by defining properties, then differentiating between physical and chemical properties.  I then gave them a sample of salt, sand, and iron filings and asked them to develop a plan, using their properties, to separate the three substances.  I offered them a list of available materials to help them out.  Considering I rushed them a bit on their experimental design process, they didn't do too terribly.

Overall, I was really impressed with my student's white boards with the exception of their particle diagrams.  I was very specific for the verbal this time:  I asked them to answer the question, "Why were we able to separate the three substances?"  I was very specific for their math as well, and told them to show me how to calculate the percent composition of the mixture.  I left the graphing and particle diagrams completely open ended, asking them to do what they felt was appropriate.

Most boards looked like this:

Strong answers to the questions, good math, appropriate method of graphing data, dreadful particle diagrams (WTF?), and an overall inability to spell the word "separating."

We addressed the particle diagram issue today.  I hope they got the point-- everyone was utterly braindead today.

Unfortunately, many of my lazy students have caught on that I don't actually grade whiteboards.  So, several groups produced garbage like this:

At least they figured out how to calculate percent composition...

Um... yeah.

I also performed the demonstration of heating iron and sulfur.  This is a demo I had never done before.  I could not get it to react with a hot stirring rod or hot splint.  I ended up using a ring stand, a heavy watch glass, and a bunsen burner.  The odor is horrific and the ignition was not all that impressive to the students.  I think the bunsen burner flame confused them- they just thought it was flammable even though I made a point of showing how far away the flame was from the iron ring.  But, they were able to see that we got a substance with different properties from either of the original two substances.  We left off with a textbook reading about pure substances vs. mixtures.

We'll do worksheet 1 on Monday.  I haven't shown them fractional distillation equipment (we don't even own any), so I suppose I should do that first!  Youtube here we come...

On a side note, my students had to take a district wide benchmark test today.  It was created with traditional pacing in mind, so many of the topics we have not covered.  When I flipped through the test, I figured there were about 11 out of 30 questions that my students should be capable of answering.  I was at least encouraged to see that my students mostly got those 11 questions correct.

Unit 3 Reflections: Icy Hot Lab Results

This is becoming the semester from h*ll.  Seriously.  Between implementing the chemistry modeling curriculum for the first time, the exceptionally unmotivated group of students, and the ridiculous number of interruptions, I'm ready to throw in the towel.

The good news:  my students' data came out better than expected.  Even in my first class, students were able to note a difference in the shape and slope of the heating and cooling curves at different points.

Some of their curves:

The bad news:  everything else.

I think maybe a handful of students at best understood what I think is a pretty easy concept.  A heating/cooling curve will have parts of the line that show little rate of change (flat) because the energy is being used to "break" the forces of attraction between the particles and change the matter into a different phase.

I don't know exactly what it is that I'm doing so terribly wrong, but I cannot get these students to care for the life of me.  I can't even get enough intrinsic respect out of them to try for me.  Two of my students today told me they hate everything about science.  I can't even fathom having the lack of respect to say that to my teacher when I was that age.  And all of this because they were asked to graph some data... which took nearly all of the 90 minutes to do, and do poorly at that.  Not that I told them that last part, but sheesh, look at those graphs-- do they look like work products that should have taken an hour to produce?!?  Notice there isn't a verbal conclusion or a particle diagram on any of them.  Let me just say there was supposed to be each of those as well.

I'm scared for the lab reports.  They are not going to be good.

Today really got me thinking about another teacher from my modeling workshop.  She mentioned that a constant problem she has with "inquiry" type labs, is that the students mess up, take away the wrong idea, and don't care enough to change their thinking.  That's very much what I saw with my students today.  I asked me students how they thought their graphs were going to look-- most said heating ice would be a straight increase, cooling the lauric acid would be a straight decrease.  After they (finally) plotted the data, I asked if that's what they saw.  Yup, they told me.  I asked about the flat areas and the zigzags-- it must have been the hot plate.  Or *maybe* it was human error.  They don't care, the line went up at a point, so they were all correct in their minds.

Can I just get a do-over on this semester?  I think if I had to do it all over again, I'd start WAY easier on this group and build up a better relationship with them.  I set the bar high and was hard on these students from the start, and they have now shut down on me.