Primary Type: Lesson Plan
Status: Published
This is a resource from CPALMS (www.cpalms.org) where all educators go for bright ideas!
Resource ID#: 155292
Behind the Scenes with Double-Replacement Reactions
In this lesson plan the students will engage in a laboratory experiment that requires them to identify the precipitate that forms when two aqueous
solutions react together. The students will apply solubility rules to determine the chemical formula and name of the precipitate that forms during the
laboratory experiment.
Subject(s): Science
Grade Level(s): 9, 10, 11, 12
Intended Audience: Educators
Suggested Technology: Microsoft Office
Instructional Time: 1 Hour(s)
Keywords: double-replacement reactions, chemical reactions, reactions, solubility rules, solubility chart
Resource Collection: FCR-STEMLearn Physical Science 2016
ATTACHMENTS
Solubility_Chart.docx
Lab_Handout.docx
Lab_Handout_Teacher_Guide.docx
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What will students know and be able to do as a result of this lesson?
Students will apply solubility rules to predict the chemical formula and name of the precipitate and aqueous solution that forms during a double-replacement reaction.
Prior Knowledge: What prior knowledge should students have for this lesson?
It is important that the student have a strong background on writing chemical formulas and naming compounds before beginning this lesson. If necessary, you may
want to review naming compounds and writing chemical formulas before beginning this lesson.
Write chemical formulas
Name binary ionic compounds and polyatomic ionic compounds
Balance chemical equations
Classify double-replacement reactions
Predict the product of a double-replacement reaction
Guiding Questions: What are the guiding questions for this lesson?
1. What type of compounds are involved in double-replacement reactions?
Ionic compounds.
2. How do ionic compounds of a double-replacement reaction react?
page 1 of 4 By exchanging cations to form two different compounds.
3. What products are formed during a double-replacement reaction?
Two new compounds are formed. They may be a precipitate (solid), a gas, or water.
4. How do you predict the states of matter of double-replacement reactions?
Use solubility rules.
Introduction: How will the teacher introduce the lesson to the students?
Lesson opener/attention getter:
1. Begin the lesson by writing the following equation on the board: Na2 CrO4 (aq) + AgNO3 (aq) ?
Show the students 2 test tubes. Test tube 1 should have 2 drops of Na2CrO4 (aq) in it, and test tube 2 should have 2 drops of AgNO3 (aq) in it.
Allow all students to observe both test tubes.
2. After the students observe the 2 test tubes, ask students the following questions:
What do you think will happen when the Na2CrO4 (aq) and AgNO3 (aq) are mixed?
Answer: Reddish brown precipitate will form.
What are the products that will form when Na2CrO4 (aq) and AgNO3 (aq) are mixed?
Answer: NaNO3 (aq) + Ag2CrO4 (s)
3. Pour the Na2CrO4 (aq) into the test tube with the AgNO3 (aq). Allow the test tube to sit for 2 minutes and then allow the students to observe the test tube.
4. After the students observe the test tube with the Na2CrO4 (aq) and AgNO3 (aq), ask students the following questions:
What rules can be used to determine which product is the precipitate and which product is the aqueous solution?
Answer: Solubility rules
What is the chemical formula and name of the precipitate that is located at the bottom of the test tube?
Answer: Ag2CrO4 (s)
Key talking points about the lesson topic:
1. Explain to the students that by utilizing the solubility rules it is possible to determine the states of matter of the products that form during a double-replacement
reaction.
2. Show the students how to use the Solubility Chart using the directions below:
If the ion is located under the soluble portion of the solubility chart then the compound that is formed is soluble (aqueous). However, if that particular ion is
attached to one of the ions located under the exceptions area of the solubility chart then the compound is insoluble and will form a solid (precipitate).
If the ion is located under the insoluble portion of the solubility chart then the compound that is formed is insoluble (precipitate). However, if that particular ion
is attached to one of the ions located under the exceptions area of the solubility chart then the compound is soluble (aqueous).
3. Solubility rules will help the students determine which product is the precipitate, and which is the aqueous solution. Therefore, if the student knows which substance
is insoluble (solid) then they can identify the solid (precipitate) in the test tube, resulting in the use of solubility rules to name the precipitate.
Investigate: What question(s) will students be investigating? What process will students follow to collect information that can be
used to answer the question(s)?
Instructions for setting up and helping students collect data:
1. Provide each laboratory group with the materials listed on the Lab Handout.
2. Students will record their experimental observations in the data table provided in the handout.
3. Reinforce the importance of stirring the solutions. Not stirring the solutions will prevent the reactants from forming the maximum amount of product. If the amount
of product is decreased then the students may not see the correct observations.
How will you check for student understanding?
As the students are performing the experiment, roam throughout the laboratory visiting each group using the delving technique to ask the following questions:
Why is it important to label the drop plate with the reactants?
Answer: To tell the difference between the various combinations of reactants.
Why is it important to stir the reactants?
Answer: Make sure the reactants react as much as possible.
Why is it important to wait 2 minutes before making observations about the products?
Answer: To provide time for the products to completely form.
Ask other open-ended questions without providing a direct answer to guide students and help them delve further into the problem.
Common errors/misconceptions to anticipate and how to respond:
Often students forget to use the solubility rules to determine which product in a double-replacement reaction will be the precipitate. Continuously remind the
students to utilize the solubility rules to determine the precipitate.
Often students become so amazed at the formation of the precipitate that they often forget to record observations of the aqueous solution that has formed. Remind
the students that the remaining aqueous solution is also important, which is the reason why they are responsible for writing its chemical formula and chemical
name as well.
Analyze: How will students organize and interpret the data collected during the investigation?
Instructions to help students organize, analyze, and interpret their data:
Organize: Refer to "Collecting Data" under the Investigate section in this lesson plan for instructions on using the data table on the lab handout.
Analyze: Instruct the students to first determine the chemical formulas of the products. Next, instruct the students to use the solubility rules to determine the state
of matter of each product.
Interpret: Instruct the students to correlate the state of matter of the products, as determined by the solubility rules, to the observations of the products obtained
from the experiment. For example, the solid that falls to the bottom of the test tube will be the precipitate and the aqueous solution is on top.
How will you check for student understanding?
page 2 of 4 As the students are performing the experiment, roam throughout the laboratory visiting each group using the delving technique to ask the following questions:
How is it possible to use only observations to distinguish between the two products?
Answer: The products separate into 2 layers, a solid layer (precipitate) and an aqueous layer.
What should you use to determine which product is the precipitate and which product is the aqueous solution?
Answer: Solubility rules
Common errors/misconceptions to anticipate and how to respond:
Refer to common errors/misconceptions under the Investigate section in this lesson plan.
Closure: What will the teacher do to bring the lesson to a close? How will the students make sense of the investigation?
For closing discussion, reiterate the connections between identifying the precipitates and aqueous solutions in the laboratory experiment to the solubility rules. Focus
on implying that without the solubility rules it would be impossible to correctly identify the chemical formulas and chemical names of the products.
Summative Assessment
The students will show they have met the learning objectives by completing the summative assessment on page 3 of the attached Lab Handout. This summative
assessment requires the students to predict the products of a double-replacement reaction and include the states of matter. The students will also use a sketch of a
test tube to label the precipitate and aqueous solution that forms from the reactants.
Formative Assessment
Specific suggestions for conducting Formative Assessment can be found in the Investigate and Analyze phases of the lesson where it says, "How will you check for
student understanding?"
The formative assessment will be a student evaluation. The student will use the evaluation to express their level of understanding about solubility rules and its
connection to writing the chemical formula and chemical name of the precipitate that forms from a double-replacement reaction.
Use the data collected from the formative assessment to guide the feedback he or she will return to the students.
The formative assessment is located on page 3 of the attached Lab Handout.
Feedback to Students
Specific suggestions for providing Feedback to Students can be found in the Investigate and Analyze phases of the lesson where it says, "Common
errors/misconceptions to anticipate and how to respond."
Since the main focus of this lesson is to connect solubility rules to identifying the chemical formula and chemical name of the precipitate, the teacher should base all
feedback on this relationship.
Record their feedback to each individual student on page 3 of the Lab Handout, next to the student evaluation.
All students should be constantly referred to using the solubility chart to determine what the precipitate will be when two aqueous solutions react.
ACCOMMODATIONS & RECOMMENDATIONS
Accommodations:
For students that may be struggling with the concept of using solubility rules to predict the state of matter of products for double-replacement reactions, a peertutor may be provided. The purpose of the peer-tutor is to constantly remind the struggling students how to read the solubility chart and its purpose for determining
the state of matter of the products.
Utilizing a peer-tutor will allow time for the educator to facilitate the entire class and not only the struggling students. The peer-tutor will take the place of the
teacher and guide the struggling student to success with completing the assigned task.
When assigning peer-tutors it is important that the educator utilize students that are capable of communication with students that are lower than they are, sensitive,
positive, and encouraging to the struggling student. Otherwise, the use of a peer-tutor will cause more destruction to the struggling child's learning process than
aid.
Extensions:
For students who master the concept of identifying and naming the precipitate, the teacher may use this activity to lead into the topic of complete ionic equations
and net ionic equations. The teacher may have these students to go back and write complete ionic and net ionic equations for each of the double-replacement
reactions that where observed during the experiment.
The teacher may also have these students to sketch test tubes and label the spectator ions and the precipitates within them.
Suggested Technology: Microsoft Office
Special Materials Needed:
Documents found in the Attachments section:
Lab_Handout.docx
Lab_Handout_Teacher_Guide.docx
Solubility_Chart.docx
Lab materials for each group:
page 3 of 4 Safety goggles
Distilled water
Spot plate (with at least 4 depressions)
Glass stirring rod
0.1 M Barium nitrate, Ba(NO3)2
0.1 M Magnesium chloride, MgCl2
0.1 M Barium chloride, BaCl2
0.2 M potassium chromate, K2CrO4
0.1 M Sodium sulfate, Na2SO4
0.2 M sodium hydroxide, NaOH
0.2 M silver nitrate, AgNO3
Labeling tape
Sharpie
Further Recommendations:
Instructions for making the solutions for the lesson opener and laboratory experiment can be found in the Flinn Scientific Reference Guide.
Disposals: Because only drops of Ba(NO3)2 (aq), Na2CrO4 (aq), Na2SO4 (aq), MgCl2 (aq), NaOH (aq), BaCl2 (aq), K2CrO4 (aq), and AgNO3 (aq) are used in this
experiment, solutions containing these materials can realistically go down the drain with excess water.
Safety:
Wear safety goggles
K2CrO4 (aq), Na2CrO4 (aq), and NaOH (aq) are toxic and can cause severe injury to the eyes and skin if contact is made.
Silver and Barium compounds are poisonous. Do not touch with bare hands, if contact is made with hands wash them thoroughly.
SOURCE AND ACCESS INFORMATION
Contributed by: Lenora Henderson
Name of Author/Source: Lenora Henderson
District/Organization of Contributor(s): Washington
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
Description
Characterize types of chemical reactions, for example: redox, acid-base, synthesis, and single and double replacement
reactions.
SC.912.P.8.8:
Remarks/Examples:
Classify chemical reactions as synthesis (combination), decomposition, single displacement (replacement), double
displacement, and combustion.
page 4 of 4