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Identifying Chemical Reactions (54 Favorites)
DEMONSTRATION in Balancing Equations, Conservation of Mass, Chemical Change. Last updated April 24, 2019.
Summary
In this demonstration, students observe a series of teacher led demonstrations to learn how to identify evidence that a chemical reaction has occurred, how to write a word equation to explain a chemical reaction, and how to convert a word equation to a balanced chemical equation.
Grade Level
High School and Middle School
NGSS Alignment
This demonstration will help prepare your students to meet the performance expectations in the following standards:
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
Objectives
By the end of this demonstration, students should be able to
- Identify evidence that a chemical reaction has occurred.
- Know the five indicators that a chemical reaction has occurred.
- Write a word equation to explain a chemical reaction.
- Convert a word equation to a balanced chemical equation.
Chemistry Topics
This demonstration supports students’ understanding of
- Chemical Reactions
- Chemical Change
- Indicators of Chemical Reactions
- Conservation of Mass
- Balancing Equations
Time
Teacher Preparation: 30-45 minutes
Lesson: 60 minutes
Materials
Demonstration 1:
- 1 test tube
- Forceps
- 1M hydrochloric acid, HCl
- Copper (Cu) metal granules
Demonstration 2:
- 1 test tube
- Forceps
- 1M hydrochloric acid, HCl
- Zinc (Zn) metal granules
Demonstration 3:
- 2 test tubes
- Solution of potassium iodide, KI
- Solution of lead (II) nitrate, Pb(NO3)2
Demonstration 4:
- 2 test tubes
- Solution of potassium thiocyanate, KSCN
- Solution of iron (III) nitrate, Fe(NO3)3
Demonstration 5:
- 2 test tubes
- Solution of potassium iodide, KI
- Aluminum nitrate, Al(NO3)3
Demonstration 6:
- Large beaker (minimum 1000 ml)
- Wire gauze
- Ethanol
- Paper towel
- Wooden splint
- Matches
- Ammonium dichromate, (NH4)2Cr2O7
Demonstration 7:
- Beaker tongs
- Bunsen burner
- Magnesium ribbon, Mg
Safety
- Wear protective gloves, clothing and eyewear for all demonstrations.
- Wash hands thoroughly after handling chemicals.
- Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.
- Only use hydrochloric acid, HCl, in a hood or well-ventilated area.
- Only use lead (II) nitrate, Pb(NO3)2, in a hood or well-ventilated area.
- Ammonium dichromate, (NH4)2Cr2O7, is toxic; use only in a hood or in well ventilated area.
- Avoid looking directly at burning magnesium.
Teacher Notes
- For more information about these demonstrations, read the associated article, My Favorite Demonstrations for Teaching Chemical Reactions, published in the May 2019 issue of Chemistry Solutions.
- To transition easily from one demonstration to the next, I set up the materials for the seven demonstrations in the following manner:
- Demonstrations 1 and 2: I place the 1M hydrochloric acid in a test tube, and each metal sample in a beaker.
- Demonstrations 3, 4, and 5: I place one of the aqueous solutions in a test tube and the other solution in a dropper bottle. Alternatively, both reactants can be placed in test tubes.
- Demonstration 6: I place ammonium dichromate in a 1000 mL beaker (or larger) with wire gauze over the opening. Since it will be ignited, I also create a wick using a small piece of paper towel soaked in ethanol. I use tongs to place the wick on top of the ammonium dichromate (like placing a candle into a birthday cake) and then use a burning wooden splint to light the wick.
- Demonstration 7: I place a precut magnesium ribbon in a beaker.
- I use a document camera to display each demonstration, which is connected to a classroom Smart Board, allowing all students to easily see the details of the reactions as they occur. Additionally, this serves as a helpful way to display the written information from the student handout next to the results.
- During the demonstrations, I compile and record information shared by my students in the data table displayed using the document camera and Smart Board.
- Before beginning a reaction, I have my students describe the appearance of the reactant(s) in the data table provided on the student handout. I direct them to record details about color, physical state, texture of the reactants, etc.
- I perform these demonstrations in the following order:
- Copper metal granules are added to 1M hydrochloric acid.
- Zinc metal granules are added to 1M hydrochloric acid.
- Aqueous solutions of potassium iodide and lead (II) nitrate are combined.
- Aqueous solutions of potassium thiocyanate and iron (III) nitrate are combined.
- Aqueous solutions of potassium iodide and aluminum nitrate are combined.
- Ammonium dichromate is ignited.
- Magnesium ribbon is ignited.
- Demonstration
Procedures:
- *Note that quantities are not indicated in the procedure, as specific amounts are not necessary. Small scale-reactions should be performed by the teacher.
Demonstration | Procedures |
1 | Add 1M HCl to test tube and place metal samples in beaker. Use forceps to transfer metal sample to beaker. |
2 | Add 1M HCl to test tube and place metal samples in beaker. Use forceps to transfer metal sample to beaker. |
3 | Pour solution from first test tube into the test tube containing the second solution sample. |
4 | Pour solution from first test tube into the test tube containing the second solution sample. |
5 | Pour solution from first test tube into the test tube containing the second solution sample. |
6 | Add ammonium dichromate to beaker. Create a wick using a small piece of paper towel and soaked in ethanol. Use tongs to place the wick on top of the ammonium dichromate (like placing a candle into a birthday cake). Use a burning wooden splint to light the wick. Once reaction begins, cover beaker with wire gauze. |
7 | Turn on Bunsen burner and use tongs to hold ribbon in flame until the ribbon starts to burn. |
- An answer key document has been included, and is available for download. Some additional information to be aware of for teachers:
- Demonstrations 1 and 5 will not produce a chemical reaction.
- Five of the reactions will produce indicators of a chemical reaction for students to observe.
- Demonstration 2, students will observe the formation of gas, as bubbles are produced when zinc metal is added to a test tube containing 1M hydrochloric acid. Additionally, they will notice the change in color of the zinc metal.
- Students should note gas formation in several of the demonstrations, including Demonstrations 2 and 6.
- Demonstrations 3, 4, and 6 will each show a distinctive color change.
- Demonstration 3 will produce a precipitate.
- Students will notice light is produced in Demonstrations 6 and 7.
- After all seven demonstrations have been completed, I work with students to develop word equations for any demonstrations that resulted in a chemical reaction.
- The final component of the activity is for students to create formula equations. I typically assist students with the equation for demonstration 2 and allow the students to complete the other equations on their own. I use this time to move around the classroom and provide individualized help to students.
For the Student
Lesson
Identifying Chemical Reactions
Part 1: Determine if there is a chemical reaction
Reactants
Appearance of reactant(s) |
Rxn
(Yes/No) |
Proof (List all that apply):
Appearance of Products |
|
1. | Copper metal + hydrochloric acid | ||
2. | Zinc metal + hydrochloric acid | ||
3. | Potassium iodide + lead (II) nitrate | ||
4. | Potassium thiocyanate + iron (III) nitrate | ||
5. | Potassium iodide + aluminum nitrate | ||
6. | Ammonium dichromate | ||
7. | Magnesium + oxygen |
Part 2: If there is a chemical reaction then complete the word equation
- Copper metal + hydrochloric acid →
- Zinc metal + hydrochloric acid →
- Potassium iodide + lead (II) nitrate →
- Potassium thiocyanate + iron (III) nitrate →
- Potassium iodide + aluminum nitrate →
- Ammonium dichromate →
- Magnesium + oxygen →
Part 3: Convert complete word equations to balanced chemical equations
- Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: - Formula Equation:
Balanced equation: