11. Chromatography – Pure Substances and Mixtures

This Friday we had a “snow day”, which means the amount of snow, or in this case freezing rain, that fell overnight rendered the roads too dangerous for sensible people to risk their lives driving to the school buses are cancelled. In our school boards the school buses get canceled but the schools never close, so all the teachers must report for duty! In addition, because it is a “regular school day” we must all carry on with activities that are directly related to the curriculum, not watching movies or playing games. (Unless they are curriculum related, of course.)

In my case, I view these “snow days “ as opportunities to do some fun labs, that I might not otherwise do, so we get the best of both worlds -- a learning activity that is related to the curriculum but a fun activity. I want to make sure that the students who show up for class have an enjoyable learning experience but those who did not make it into school are not left behind in the dust.

Our grade nine class is deep into the chemistry unit at present. We have mastered the concept that matter is subdivided into pure substances and mixtures, etc. So we took the time of Friday to do a simple Smarter Science chromatography lab to explore mixtures and pure substances further.

1. Initiate and Plan = ENGAGE

I started the class by explaining chromatography to them in real simple terms. I modelled how I could put samples on a start line on filter paper and place the bottom of the paper into a beaker with a small amount of water in it. The water moved up the paper by capillary action dragging the components of the sample with it. Before class I had prepared several chromatography papers which I dried and showed to the students. In all cases the samples I used were dots of ink from a variety of markers that I had lying around my classroom. When we examined the finished chromatographs we could observe either one solid coloured line or a line that split into a prism of colours. I posed the questions “Which inks made solid lines and which inks split into a prism of colours?” the students were quick to assert that if more than one colour could be seen in the chromatograph the ink must have been a mixture whereas chromatographs with a solid colour must have been a pure substance.

I then distributed the Smarter Science starburst diagram so we could determine all the variables that could be controlled or tested for in a similar experiment that the students would run. We brainstormed six items.

1. The amount of time the chromatograph was run

2. The amount of liquid placed in the bottom of the beaker

3. The size of the ink dot

4. The colour of the markers

5. The brand of the markers

6. Size of paper

The students discussed the list of variables with their partner to decide which one they would test for. They moved the post it note with their dependent variable to the head of the fish diagram. The other post it notes became their independent variables and were moved to the “bones of the fish diagram.

2. Perform and Record = EXPLORE

The partners continued to design their experiments by planning the values to give each on the independent variable, ie. How long to run the experiment, how much water to use, what brand of markers to use, etc. Once they had determined their variables they began experimenting.

Yet again I had the pleasure of watching student’s experience a lab technique for the first time and react in wonder. When the inks actually began running up the paper they were amazed! This short video clip illustrates the joy experienced by one group as they produced a rainbow.

3. Analyze and Interpret = EXPLAIN

The students analyzed their chromatographs to determine if the various inks they used were pure substances or mixtures. They compared their results with each other while classifying their inks.

4. Communicate = EXTEND

Because it was a snow day and these students had actually made the effort to come to school I allowed them extra time to reflect on this lab and play with the technique. I had them explain their results to me orally and write a one sentence conclusion.

N.B. The students were pleased that although they had come to class on a snow day they “didn’t have to do any work” and were allowed to experiment instead! After the lunch break we blew up a gummi bear and a sour patch kid (two different types of candies), in two separate explosions, using potassium chlorate. We followed up with a discussion of which one caused the greater reaction therefore contained the most reactant (sugar). Then we played a Periodic Table game using the smart board wherein they had to identify elements by the number of orbitals and outer most electrons they contained. Lot’ s of fun! No work! And even the administration is happy!

Posting Ten -- Discovering Physical and Chemical Properties

We’ve had a few more signs that winter is coming to Ottawa – a freezing rain storm last night resulted in a number of fender benders, including people smashing into ambulances and pedestrians falling down and breaking their bones. Yet in the classroom we persevere, the courses march ever onwards, we are over half way through the first semester now, midterm report cards have gone home, time marches on!

This week the grade nine applied science class started the chemistry unit (aka Exploring Matter) which lends itself to so many fun labs. It is important for the experienced teacher to remember that what has become ho-hum for them is new and exciting for the grade nine learner, who is often experiencing doing chemistry “in a real lab” for the first time! To that end I always make sure that the student has as authentic an experience as possible, which is easily accomplished if they wear safety goggles and use “real” scientific equipment instead of paper cups and plastic spoons. That being said I am fortunate to have an actual lab with real equipment, but the same results can be achieved using materials that are at hand.

I have taught the concept of physical and chemical properties many times and have always used a cook book lab as a follow up to the theory. This year I wanted to use the Smarter Science technique of having the students plan their own lab so I designed a table for them to use wherein they both designed the procedure and recorded their observations.

1. Initiate and Plan = ENGAGE

The students were instructed to test hair, magnesium and brom thymol blue for physical and chemical properties. The properties to be tested for were identified on the table provided.

Since we had already done a couple of labs this week the students were familiar with the equipment we have available and where it is kept. They were instructed to come up with a method of testing for each of the following physical properties: colour, lustre, solubility, density and texture as well as the chemical properties: combustibility, reaction with oxygen and reaction with acid. Only when they had filled in the middle column of the handout (above) were they allowed to gather the needed materials together.

2. Perform and Record = EXPLORE

The students’ favourite part of every lab is experimenting and recording and, as usual, they were enthusiastic participants. Although they had candles to test for combustibility the flame did not get hot enough for two of the groups to experience success with the magnesium so I brought them up to the fume hood where I have a Bunsen burner and let them use it. Wow!

3. Analyze and Interpret = EXPLAIN

In order to help the students analyze their results I posed the question “what is the difference between physical and chemical properties?” This question prompted them to review their table and analyze the techniques they had used when testing for physical versus chemical properties.

4. Communicate = EXTEND

Upon reflection most of the students were able to explain that physical properties could be detected using one of the five senses but chemical properties required a reaction, which did not seem to be reversible.

Why I love teaching!

My own favourite moment during this lab was when my shy ESL student completed her lab then came over to a group of yahoos who were dithering around , asked them if they had reacted acid with their brom thymol blue yet and proceeded to do it for them. Wowie - Zowie! They thought she was magical when the solution turned yellow. They quickly got their act together to test everything themselves. Seriously, it was beautiful! This girl had never even spoken to these rowdy boys before and now she had not only spoken to them but demonstrated her learning to them! Major props all round!

What about you? Why do you love teaching? Have you tried using the Smarter Science framework yet? Is this blog helpful to you? Please leave us a comment.

Posting Nine -- Grade 11 University Biology Frog Dissections – Smarter Science?

Today was frog dissection day, a highlight of the course! Probably the only better lab is the fetal pig dissection! Although I went through a stage where I no longer wanted to dissect preserved specimens with my classes there is so much learning that occurs during these two events that I have grown to love them and even look forward to the students’ nervous excitement.

Here’s how the frog dissection lab unfolds in my laboratory. The students work in groups of two or three. Each group is given a carefully produced dissection guide and accompanying work package. By reading the guide and following the directions they are guided through the hands-on dissection in such a manner that the written answers to the questions are self-evident. Naturally some of them do not bother to read or follow the directions so they struggle with the questions.

Is this Smarter Science? Is it a collaborative inquiry based activity? Let’s look at it a little more carefully.

In the weeks leading up to the frog dissection the students have studied the “Internal systems Unit” of the curriculum. In grade 11 this includes the digestive system, the circulatory system and the respiratory system.

Step one of Smarter Science is INITIATE AND PLAN (aka Engage). The students have been questioning, predicting , hypothesizing and inferring what the actual dissection will be like during the previous lessons while we have been studying the theory. Looks like I can check step one off.

Step two of Smarter science is Perform and Record (aka Explore). This is a carefully guided dissection so the students do NOT design their own experiment. They do, however, use instruments, record, gather data, demonstrate and experiment. Hmmm . . looks like I can check this one off.

Step three of Smarter Science is Analyze and Interpret (aka Explain). This is where the work package comes in! The questions have been designed in such a way that the students have to analyze, evaluate and review what they are doing constantly. The questions do not require simple “yes” or “no” answers. Rather they force the students to draw on their prior knowledge, discuss amongst themselves and decide, collaboratively on the appropriate responses. . . . which leads us directly to step four!

Step four of Smarter Science is Communicate (aka Extend). So now the students are discussing, explaining, reporting, writing, reflecting and teaching each other. Check, check and check!

So why didn’t I think this activity was Smarter Science? Let me review what Smarter Science is: “ . . . . is an open-source, engaging framework for teaching and learning science in grades 1-12 and for developing the skills of inquiry, creativity and innovation in a meaningful and engaging manner.”

Right! So I didn’t use the framework directly but we were inquiring in a creative, innovative, meaningful and engaging manner.

What do you think? Please write your comments in the box below.

Posting Eight -- A Reflection

We are half way through semester one and I am totally convinced of the success of using the Smarter Science framework with the grade nine applied science class. I have never had such an engaged class! The students can’t wait to get to class each day and are eager to take on any task! In fact we are currently doing our unit review in preparation for the test on electricity and they are completely engaged in this seat work! Probably because they completely understand the theory and they know that once this is over we will be exploring chemistry using the same inquiry-based learning.

In the meanwhile my own thought s are starting to drift towards next semester when my teaching schedule will include a locally developed (essential level) science class. I have been wondering how inquiry-based learning will work with them since my past experiences have shown me that these learners often have difficulty ordering their thoughts and even greater difficulty following a lab procedure. It was with these thoughts on my mind that I entered the school one morning this week. On the way to my classroom I encountered Patrick, a high needs student, who has been in my locally developed science class for two semesters in the past.

Although I greet Patrick every morning he does not always greet me. He is often locked in his own thoughts. This is the way our conversation went on this particular day:

Me: “Hi Patrick!”

Patrick : “Hi. . . Hey? . . .”

Me: “Yes?”

Patrick : “Do you like science?”

Me: “I love science!”

Patrick : “Well, if you like science . . . there is something I was wondering about . . .”

Me: “Yes? What were you wondering?”

Patrick : “Well . . . Could I become invisible?”

Me: “Invisible? Do you think you could become invisible?”

Patrick : “Well . . . I was wondering about it and I think that is science.”

Me: “Hmmm”

Patrick : “Well . . . you like science and I am wondering if I could become invisible.”

Me: “That is a very good question, Patrick. I think scientists would like to experiment with you becoming invisible. Would you like that?”

Patrick : “Yes! . . . invisible . . .I’m wondering . . . “

At this point Patrick drifted off and so did I. The more I think about it the more I think that inquiry-based science is exactly what my locally developed class needs. What do you think? Please feel free to post your comments.