Monday, November 22, 2010

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.

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