Perhaps the first assay we learned in science class was the starch test, where we dropped iodine on a substance, and if it turned “blue-black”, it indicated the presence of starch.

Now, as modern-day science teachers, we carry on the wisdom of generations of science teachers, and continue to avoid calling the positive result “black and blue”, as no science teacher wants students to associate bruises with white bread or potatoes.

The starch test has become such a common test, that I believe the term “starch test” should replace “litmus test” as the analogy cliché for social or political tests. (For example, Wikipedia states, “A litmus test is a question asked of a potential candidate for high office, the answer to which would determine whether the nominating official would choose to proceed with the appointment or nomination.”) How many non-science teachers even know what litmus is or what a litmus test is? Let’s start using analogies more people can relate to. [People would really start liken that (with an intended pun on the nature of litmus)!]

Today is the six-month anniversary of this blog. It seems such a short time ago, but alas, on June 20, 2008, my first blog was posted. This made me wonder, “How does one know if one is successful after just six short months?

To find the answer to this query, I did a search on blogs. I found no numerical metrics for success. Looking at the latest report from Google Analytics, I did see that more than 35 people per day have read this blog, and that this month alone, there were over 1,000 readers from 70 countries/territories.

The search for blogs about blogs (i.e. metablogs) yielded no numbers, which I viewed once again as evidence that collective wisdom can often be found in groups of people. The qualitative metric I did derive, however, from reading the advice of more experienced blog pundits was this: If a blogger enjoys writing about their interests, and some people are reading, then it should be considered successful. As far as this starch test is concerned, I judge this blog as a success, and I thank you for reading it.

But now on to science teaching and technology, which is the focus of this blog. In the living world, photosynthesis is one of the most important processes. Fortunately, Adaptive Curriculum has a free interactive activity that teachers and students (from all 70 countries/territories) can use to learn more about photosynthesis. In “Plants Needs for Photosynthesis” students conduct several investigations, where they can add or subtract water, light, carbon dioxide, and oxygen. The plant then does its thing (AKA: metabolism) for four hours.

After this, the starch test is performed to see if photosynthesis occurred. In the starch test, the leaves are boiled and then dipped into hot alcohol to remove the green chlorophyll. Next, the leaves are dipped into room temperature water. Finally, drops of iodine are placed upon the leaves. Through these discovery-based learning experiences, students are able to determine the conditions that are needed for photosynthesis to occur.  

Thank you to Adaptive Curriculum for giving us this free Flash-based activity, and for their support of this blog. And no matter what your starch test or litmus test for happiness may be, I wish you a happy holiday season.

Resources:

If you (or your students) don’t know what a litmus test is, here are some links:

Adaptive Curriculum’s “The Properties of Acids”

Adaptive Curriculum’s “The Properties of Bases”

Adler, Kris Lesson Plan: The pH scale. 

Whether at the high school or middle school level, students studying graphs of motion are often confused. One area of confusion occurs in the difference between distance-time graphs and displacement-time graphs. Virtual activities can cause more confusion, unless the right ones are chosen.

Distance-time graphs are a part of many middle school math and science curricula. A Google search for “distance-time graphs” reveals about 10,500 websites with many Java-based and Flash-based online activities. The problem for physics learners and teachers is that in many cases, the developers call their graph a distance-time graph but in reality they are displacement-time graphs.

Here are some examples of (otherwise) good websites making this error:

Moving Man 

Football (soccer) Distance Time Graph

GCSE Bitesize 

There are a few good sites that accurately portray distance-time graphs.

“Crocodile-clips” is a simple, free site where students move a helicopter and create a real-time distance-time graph. It doesn’t matter if the helicopter is moved away from or closer to the starting point. The true distance traveled is displayed on the graph. It is simple but effective.

Commonwealth Curriculum Pack (CCP) is a more involved site. I used this with my mixed age physics class last week and it made the point and kept their interest.

This site uses the context of the 100-meter race to show different arrival speeds. Quickly, my students learned that the steeper the slope (gradient), the greater the speed of the runner. Then we viewed several nice animated sequences of interpolation, which they then interpreted.

PBS Teacher Line http://www.pbs.org/teacherline/resources/activities/race/readings/race.htm.

Students observe stick figures run 400-meter races. They can see the runners move at actual speeds or average speeds, so this serves as a good way to help students understand instantaneous speed versus average speed.

Motion graphs will probably always be confusing for some students. We can reduce confusion with distance-time and displacement-time graphs by using internet resources that accurately portray the difference.

Additional Resources

Adaptive Curriculum’s Activity Object: “Truck On: Position and Velocity-Time Graphs” 

The Physics Classroom Tutorial: Distance and Displacement