Week 8 - September 20, 2018 Chemical/Physical Properties and Physical/Changes

This week we didn't watch an introductory video lesson, but we nevertheless had a jam-packed day! First we defined and discussed what physical and chemical properties were in general and I provided examples of each. I told student not to concern themselves with taking notes, but to listen and follow along because they would write the notes for homework as shown below:

Homework Notes Page 1

I am taking pictures of the notes rather than putting a powerpoint slide of the notes up because I want the kids to hand write their notes rather than printing and gluing them in. Studies have shown that writing helps kids to better retain information. After our class discussion on physical and chemical properties and physical and chemical changes, students broke into small groups and did a sorting activity where they had to distinguish between various physical and chemical changes. After a class discussion on which items showed chemical changes and which showed physical changes, we were able to establish a few things: 1. Life processes  and cooking typically involve chemical changes. 2. Physical changes alter the appearance of material, but not the identity of the material.

Next, we discussed how to tell that a chemical change (reaction) has occurred. I performed 4 demos that demonstrated the evidence we can use to determine that a chemical reaction has occurred. In the first demo, I placed Nerds candy into a balloon and then covered the mouth of a Pepsi with the balloon. When I added the Nerds candy to the soda, gas was produced and collected in the balloon. This led to our first piece of evidence that a chemical reaction had occurred--the production of a gas. This demo also helped us to understand the Law of Conservation of Mass. In a closed system, the amount of material we begin with is the same amount of material that will be present once a reaction has occurred. Next, I did a demo where Red Bull energy drink was combined with milk to produce a precipitate (solid). In the third demo, I added blue food coloring to bleach and after shaking vigorously for a minute there was a color change denoted by the absence of blue food coloring. There was a return to the original color of the bleach. The last demo was the activation of a hand warmer by shaking the contents in the hand warmer packet. Heat was given off because the interactions of the contents in the packet generated heat in an exothermic reaction.

Students were given a graphic organizer below, which they colored similar to the sample below:

A copy of the graphic organizer for students who were absent can be found at this link. Evidence a Chemical Reaction Foldable

The additional notes that should be written under each flap are shown below.

It was time to apply all that we learned to our lab "Determining the Identity of an Unknown Substance". Students were given 6 different "known" powders and one mystery powder. Using 4 different indicators (water, vinegar, iodine, and cabbage juice), they were to observe the reactions that occurred, document the evidence that a chemical reaction had occurred for each powder, and use the information they gained to identify the "mystery" powder. While each group worked at slightly different paces, I was pleased that they all determined the identity of their mystery powder correctly