Eric Girard A B SHEPARD HIGH School (CAMPUS), PALOS HEIGHTS, IL
High School Chemistry : Unit #3 - Unit 5 Chemical Reactions : Lesson #2

Can a Gummy Bear Build Curiosity About Chemical Reactions?

Objective: SWBAT describe how physical and chemical properties can change during a chemical reaction.
Standards: HS-PS1-7 SP1 XC-EM-MS-1
Subject(s): Science
60 minutes
1 Introduction - 0 minutes

This is the second lesson in the unit which covers NGSS HS-PS1-7, the uses of mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction; and DCI-PS1.B, the fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions. This lesson is a continuation of the previous day’s lesson where students build a foundation for understanding chemical reactions. In the previous lessons students wrote questions based on textbook reading.  Today students will use the textbook to answer another student's questions.

After students have developed an overview of the unit, students will view a demonstration of a chemical reaction.  The purpose of this is to introduce students to chemical reactions and learn the difference between open and closed-ended questions.  By continuing to develop scientific questioning they will become more proficient at the NGSS Scientific Practice 1, developing questions.

During this lesson students will recognize that energy and matter is an underlying NGSS Crosscutting concept involved in all chemical reactions.  This is not the main focus of this lesson, but as students continue to develop an understanding of chemical reactions throughout the unit they will build on the idea that matter and energy are conserved in chemical reactions.

2 Engage - 15 minutes

This is the second day where I provide students with next year’s course recommendations.  The first portion of the class is providing them with a brief overview of third year science classes offered.  I also provide a brief explanation of what classes will fit specific academic and future educational goals.  Most students will take physics as a third year science, but I specifically speak with each student to provide a recommendation that fits their goals.  While I am speaking with students they will be required to work independently on the day’s assignment.

The previous day’s lesson had students read two sections in their textbook on chemical reactions and write questions about the content.  Students were asked to write questions that could be answered by other students using the textbook.  After writing the questions they traded their questions with another student.  They then answered the questions based on the textbook information.

As an extension to this activity we start class with each student sharing a question and answer.  The only stipulation that I have is that there be no repeat questions, so that all students provide something new for the class.  For example, I don’t want two questions that ask about products that are phrased differently. 

Examples of student’s questions and answers:

  1. What is a precipitate?  Evidence of a chemical reaction based on a insoluble solid that occurs.
  2. What is an example of a decomposition reaction?  Hydrogen peroxide breaking down into water and oxygen.
  3. What does the the letter (s) mean in a chemical reaction?  Solid.

These are a couple of simple questions that students answered.  More can be seen in the following screencast of one student's question and answer sheet.

As we finish sharing questions, I have students turn in their questions and get out their journals for the next part of the lesson. 

3 Explore (Demonstration) - 15 minutes

For this part of the lesson I will teach students another questioning technique by having students make observations about a chemical reaction and develop questions based on their observations.

For this demonstration I show my students something called the Gummy Bear Sacrifice.  This is a fairly simple demonstration that requires little preparation, supplies and time, but develops a lot student curiosity and questioning. If a fume hood is not present a YouTube video can be shown in the demo place.

Prior to the bell ringing I have the demo ready to go.  This builds curiosity because most students love demos and always have questions. 

Demo Preparation

At the teachers lab table I have a red gummy bear laying on an "altar" (3 small wooden blocks) with 4 pins pushed into it.  Surrounding the red gummy bear are several orange, green and clear gummy bears.  In the fume hood I have the ring stand, test tube clamp and test tube set up.  I also have the Bunsen burner, potassium chlorate (KClO3), spatula and lighter ready to go.  This way when I bring the gummy bear over I am ready to go.

I then ask, “who likes gummy bears?”  Followed by, “what is your favorite color?”

Eventually someone says red…which leads me to my story about red gummy bears being the most abundant gummy bear in the pack and that none of the other gummy bears like being bullied by the red gummy bears. So they decided to overthrow the red gummy bear and sacrifice one to teach the other gummy bears not to bully anymore.  I have been known to throw in an analogy to Hunger Games depending on the mood of the class.

At this point I put the gummy bear on the watch glass and tell the class to walk over to the fume hood.  While around the fume hood I tell the class that it is important to make as many observations about how the sacrifice is being performed, so that it can be repeated if another read gummy bear decided to be a bully.  This helps students pay attention so that they will be able to create questions after the demo.

Now that all students are paying attention I begin the chemical portion of the demonstration in the fume hood. 

Materials needed:  Gummy bears, large test tube, Bunsen burner, ring stand, test tube clamp, spatula, lighter, KClO3, fume hood, dissection pins, 3 small blocks of wood (optional) and a watch glass

Safety:  This demonstration should be performed in a fume hood due to smoke that is emitted from the second part of the reaction.  Googles and lab coat should be worn.

Demo Procedures:

Ask a student to take the pins out of the gummy bear.

  1. Scoop KClO3 into the test tube.  Don’t use too much; 3 scoops should be good (1 cm from bottom of test tube).
  2. Light Bunsen burner and gentle heat test tube till KClO3 is melted.  Do not use a direct flame.  Hold the Bunsen burner and gentle wave the flame under the test tube so it does not get too hot.
  3. Make a note to students to observe what is occurring to the KClO3
  4. After the KClO3 has melted add the gummy bear using tongs and close the hood door completely.
  5. While I am adding the gummy bear, I ask students to listen closely and they might be able to hear the gummy bear scream.  If you have ever done this demo before you know that this reaction is quite vigorous and produces a lot of light, heat and sound (screaming). 
  6. Ask students to go back to seats after reaction is complete.

This demo is really easy to set up, and produce a lot of information about chemical reactions.  While I am doing the demo I don’t speak much about what is occurring and only continue talking about how bad red gummy bears are. 

While I am doing this students always have a bunch of questions.  I simply tell them to keep those questions in mind and they will be addressed after the sacrifice.  I don’t say much about the reaction process other than telling them that the white chemical is potassium chlorate.

My objective for being none nondescript about the reaction is to build curiosity about chemical reactions.  This technique works very well!  Students have lots of questions and tend to realize more about what is happening when less is said by me.  They will be able to scaffold what they know from the textbook reading, to what they saw in the demonstration, to what they will learn later in the unit.

4 Explore (Questioning) - 15 minutes

I like to call this part of the lesson, questioning 2.0.  Because the previous day’s lesson, and the 1st part of this lesson, had students develop questions that had little structure.  This part of the lesson will begin to teach students about the difference between open and closed-ended questions and how to structure questions with a focus.

Now that students have seen the demo, built curiosity and developed questions in their head, I provide instruction about what to do with what they've seen from the demo.

On the board I have the following instructions:

Open and closed-ended questioning requirements:

1.     Ask as many questions as you can.

2.     Do not stop to judge, discuss, edit, or answer any question.

3.     Write down every question exactly as it was asked.

4.     Change any statements into questions.

I direct their attention to the board and ask, “does anyone knows the difference between an open and closed-ended question?”  I am looking for the answer that an open question will have more than one answer and a closed question will have a definite answer and often be answered with a yes or no (but does not necessarily be answered yes or no).  An example of an closed-ended question that is not a yes or no would be, "what substance needs to be used in the Gummy Bear Sacrifice?"  Potassium perchlorate.

After the difference between the two is established, I instruct students to follow the criteria on the board and write as many questions in their journals based on the demo that come to mind .  I tell them not to judge the question, and write it down as it was phrased.  Do this in 3-5 minutes.  For clarity I let them know that any question about the demo is fair game.  For example, if you have a question, “is the test tube glass?” then write it down. 

During the question writing I am walking around to encouraging them to not judge their questions, that this is brainstorming questioning and they should have at least 5 questions.  This motivates some of the students that are afraid to ask a bad question.

After several minutes I take volunteers to provide a question. Typically lots of students want to provide questions because they truly are curious about the demo.

Two popular question that many students have are, “will the reaction occur if the powder isn’t melted?” (close-ended) and “what would happen with a different color gummy bear?” (open-ended).  The first question is a classic example of a close-ended question because the answer is "no".  The second question mention is open-ended because it will require a more in-depth answer that would need further investigation or research to answer.

After each volunteer I ask them to state whether their question was open or closed-ended.  I also ask them to think about what type of question is more testable, and which type of question can lead to further questioning.  Closed-end questions are more testable and more easily answered.

This is step helps students become more proficient in at the SP of questioning.

5 Practice - 5 minutes

After a few sample questions and brief discussion, I instruct them to go through their list of questions and decide if it is an open ended or close ended question.  I simply tell them to put an “O” or a “C” next to the question.  While they are doing this I walk around checking for accuracy.  This process is beneficial because it gets them to re-read their questions and begin to prioritize what questions are well thought out and written well.

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The next class period will build on this by having students taking an open-ended question and changing it to a close-ended question, and vice versa.  Followed up by prioritizing what questions will be good for research and what questions are more testable,