Beacon Lesson Plan Library

Solids Rule as Precipitates Form

Rosemary Wilson
Santa Rosa District Schools

Description

Students mix two solutions containing dissolved ions, one containing calcium and the other containing carbonate, which form the precipitate CaCO3. Stoichiometry can be employed to determine the actual yield and percent yield of the product.

Objectives

The student knows that connections (bonds) form between substances when outer-shell electrons are either transferred or shared between their atoms, changing the properties of substances.

The student knows that the chemical elements that make up the molecules of living things are combined and recombined in different ways.

The student knows that scientists control conditions in order to obtain evidence, but when that is not possible for practical or ethical reasons, they try to observe a wide range of natural occurrences to discern patterns.

Materials

1. Ring stand
2. Iron ring
3. Glass funnel
4. Filter paper
5. Wash bottle
6. Two 100 mL beakers
7. One 250 mL beaker
8. Balance
9. Stirring rod
10. 0.1 M Na2CO3
11. 0.1 M Ca(NO3)2
12. 10 mL graduated cylinder

Preparations

1. Prepare 0.1 M solutions of Na2CO3 and Ca(NO3)2.
2. Assemble all the required equipment on a cart or your demonstration table.
3. Prepare lab report sheets for students’ use. (included in attachment)
4. Prepare lab rubric sheets for students’ use. (included in attachment)
5. Prepare students by lecturing on precipitate formation from a double replacement reaction or by lecturing on stoichiometry if you want that application in this lab.

Procedures

This lab can be accomplished using small volumes to show precipitate formation, or the volumes of the solutions can be increased so that stoichiometry can be employed.
1. Have the materials ready on a lab cart or demonstration table.

2. On the teacher’s demonstration table, show the students how to set up the apparatus for this lab.

3. Attach the iron ring to the ring stand.

4. Explain to the students that chemists sometimes filter to obtain the solid which has formed and sometimes they filter to obtain the liquid which is called the filtrate. In this case, the students want to obtain the solid formed, the precipitate.

5. Show the students how to correctly fold a filter paper so that it will fit properly in the funnel. Show the students how to use the wash bottle to wet the paper so it will adhere to the sides of the funnel.

6. Pour 10 mL of each solution into the demonstrator’s beakers. Using the 250 mL beaker, mix the two solutions showing the precipitate’s immediate formation.

7. Using the stirring rod, show the students how to decant the liquid to the surface of the filter paper.

8. If you want the students to employ stoichiometry with this lab, increase the volumes of the solutions and tell them to place their filter paper at a designated site so the water will evaporate and the solid can be scraped off the paper to be weighed.

9. After successful demonstration of the lab technique, distribute the lab sheets (copies of lab report are included as an attachment) and allow them to proceed with the experiment.

10. Circulate around the lab areas helping with set-up problems and proper measuring techniques.

11. At the end of the experiment, instruct the students to clean their laboratory areas and replace all the equipment on the cart or demonstration table.

Assessments

1. Lab reports are to be completed by students and graded according to content and construction.
2. Include the question, ‘What is the term used for a solid which falls out of a solution?’on the chapter test.

Extensions

1. Students need the knowledge of precipitates, solutions, double replacement reactions and stoichiometry (if that is to be employed.)
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