Now It's Your Turn to Identify the Reaction

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Objective

TSWBAT identify five different types of chemical reactions based on how reactants form products.

Big Idea

Students perform demos that illustrate the 5 types of chemical reactions and determine what type of reaction they are observing.

Introduction

Performance Expectation (PE)/Disciplinary Core Idea (DCI)

This lesson is aligned with 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.  Student were introduced the previous day to the 5 different chemical reactions that show that conservation of mass can occur several of ways during a chemical reaction. Today they will performing a series of reaction identifying the type of reaction and predicting the gaseous products of combustion and single replacement reactions.  

Science and Engineering Practices (SEP)

This activity has students Analyzing and interpreting data by comparing five different types of reactions.  Students will gather qualitative data from each reaction, look at the reactants and products formed and determine what type of reaction is occurring.   

Crosscutting Concepts (XC)

During this lesson students will recognize that patterns occur in science.  Students are expected to see that patterns exist in each of the 5 types of reactions and be able to recognize the reaction based on these patterns.

Lab set up

60 minutes

This lab is set up into 8 separate stations (Types of Chemical Reactions Lab) that require a variety of materials per station.  Set up is approximately one hour if you have to make and fill dropper bottles with hydrochloric acid.  Most of the stations require a only supplies.

Safety concerns for each station.

I walk around prior to the activity and make students aware of safety concerns for each station.  All students should wear goggles and apron throughout the lab.

Station 1: Students should be careful not to touch the test tubes that are collecting gas.

Station 2: Don't get acid on hands, pour waste down the sink and rinse test tube

Station 3:  Don't dumb metal down the drain, don't get the copper chloride on skin, dispose of aluminum ball in waste beaker.

Station 4:   Don't look directly at the burning magnesium ribbon, be careful lighting lighting the Bunsen burner.

Station 5:  Don't get chemicals on hands, dump waste down sink and rinse test tube.

Station 6:  Don't look into test tube when placing wooden splint in test tube, dispose of solid waste in waste beaker, rinse test tube.

Station 7:  Don't get acid on hands, do not look into the test tube because it will have a small pop, dispose of solid waste in beaker, rinse test tube.

Station 8:  I perform this as a demo 1st and have students observe and predict products.    

Materials

  • 4 dropper bottles of 1 M HCL
  • 6% hydrogen peroxide
  • Magnesium ribbon
  • Copper wire or sheet
  • Iron metal
  • Mossy zinc
  • Calcium carbonate
  • 6 test tubes and test tube holders
  • Wooden splints
  • Lighter of matches
  • 2 spatula
  • 2 forceps
  • 8 beakers for waste
  • Two petri dishes

Lab exploration

35 minutes

As explained in the previous section the stations are set up around the room into a separate stations.  Students spend approximately 4 minutes at a station before told to move the next station.  During the time at each station should need to accomplish the task that is written on each instruction sheet, write down the chemical equation, take notes, provided evidence for a chemical reaction and clean up the station (see student work).  This is initially a lot for students to do in a 4 minutes, but after 2 stations they get the hang of the procedures and complete the task in the allotted time.

Before starting the lab I demonstrate the pattern that will be followed.  This can very easily over looked but can make the difference between confusion and a successful lab.  I also tell students that must remain at the lab station till time is given.  I let them know that they can work on finishing previous stations information, such as classifying reaction, from the data that was collecting.

I also urge them to look at the front page of their lab report and use the evidence for chemical reactions to aid them in completing the lab.  On the front page students will see different ways to identify evidence of a chemical reaction.

After having many students struggle on this activity and not complete all portions of the lab report for each station, I decided not to grade it and thought it would be more beneficial to go over it as a class.  I believe that many students struggled because they don't have the necessary background knowledge to tie all aspects of the unit together.  I only took one day to do this lab and I think it could have been spread out into two days by giving students a longer opportunity at each station. Next time I perform this activity I will treat it more as a reinforcement lab than a assessment. This can be done by making sure each student understands important aspects of the reaction at every station, such as how to balance the chemical equation, what observations where used for evidence and how predict the product when necessary, before moving on to the next station.

Conclusion/Homework

5 minutes

After the brief introduction and 3 to 4 minutes at each station, little time is left to summarize the what was learned.  The main goal of the last part of the class is to let students discuss the seven stations with their group and reflect upon their observations from each station.  

As they sitting with their groups I am walking around helping students predict the products and looking to see who had difficulty determining the type of reaction.  

After performing this lesson for several years I have determined that this activity is very difficult for basic chemistry students, only having a limited amount of chemistry knowledge.  I find that it requires them to be able to synthesize a years worth of chemistry and apply it to a relatively new concept of predicting products.

 Having students predict the product is the inquiry portion of the lesson is not meant to be weighted as the main objective of the lesson.  My expectation for students is to mainly have them see that many of the products in our reactions are gases and can't be seen.  So mass is conserved even if the products present in the reaction vessel weigh less than the reactants (or more in the case of the magnesium burning.

 If students have difficulty predicting products, I do not deduct points as long as effort to predict them has been put forth.