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.