Summary
Overview
This lab discusses types of reactions and replaces traditional reaction experiments involving chemicals such as lead (II) nitrate, barium chloride, and silver nitrate with greener alternatives. This lab is designed to challenge students to identify types of chemical reactions and distinguish between those that use safer, less hazardous chemicals and those that are more dangerous. Students will make a choice as to which reaction they will perform using the 12 Principles of Green Chemistry. They will ultimately learn the difference between composition, decomposition, single-displacement, and double-displacement reactions.
Learning Objectives
Students will:
- Perform composition, decomposition, single-displacement, and double-displacement reactions
- Make observations of chemical reactions and categorize them
- Write and balance chemical equations
- Analyze the reactions against the 12 Principles of Green Chemistry
NGSS Alignment
- HS-PS1-1. Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
- HS-PS1-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns in chemical properties.
- HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
Materials
Per group of 2-3 students:
- Goggles
- Gloves
- 2 (10 mL) graduated cylinders
- 3 test tubes
- Magnesium strip
- Steel wool
- 3 M hydrochloric acid
- Zinc strip or galvanized nail
- 5 mL 0.1 M copper (II) chloride solution
- 5 mL 0.1 M copper (II) sulfate solution
- 5 mL 0.1 M potassium carbonate solution
- 5 mL 0.1 M sodium carbonate solution
- 5 mL 0.1 M calcium chloride solution
- 5 mL hydrogen peroxide (5-6%)
- Potato piece (catalase). Alternative sources of catalase like yeast or liver (chicken or beef) can be substituted.
- Calcium oxide
- Copper wire
- Rubber stopper
- Wooden splint
- Match
- Calcium carbonate chips
- Wire gauze
- Bunsen burner
- Scoopula
Safety Information
- Hydrochloric acid at lower concentrations is a skin irritant and, if it comes into contact with the skin, should be washed with soap and water.
- Copper (II) sulfate is a skin irritant and, if it comes into contact with the skin, should be washed with soap and water.
- One reaction uses a wooden splint to test for the generation of gases, which involves the use of matches in the classroom; proper safety using matches should be practiced.
- Another reaction involves the use of a Bunsen burner; exercise proper laboratory safety when using the Bunsen burner.
Background Information for Teachers
There are five types of chemical reactions: composition (also called synthesis or combination), decomposition, single replacement, double replacement, and combustion. This lab will cover all but combustion.
Composition is the combining of two or more substances to make a single more complex compound. It can be depicted as:
Decomposition is the breaking down of a more complex compound into simpler substances. Decomposition and composition are opposites. Decomposition can be depicted as:
Single replacement is a reaction where an element replaces a similar element in a compound. It is also called single displacement. Single replacement can be depicted as:
Double replacement is a reaction where the positive and negative ions in two ionic compounds switch places to form two new compounds. It is also called double displacement. Double replacement can be depicted as:
In green chemistry a set of twelve principles guide chemists to choose reactants that result in the safest, most economical, and environmentally sound reactions to create a product with the desired properties. Information about the goals of green chemistry and the twelve guiding principles is available from Beyond Benign.
Safety Information
- Hydrochloric acid at lower concentrations is a skin irritant and, if it comes into contact with the skin, should be washed with soap and water.
- Copper (II) sulfate is a skin irritant and, if it comes into contact with the skin, should be washed with soap and water.
- One reaction uses a wooden splint to test for the generation of gases, which involves the use of matches in the classroom; proper safety using matches should be practiced.
- Another reaction involves the use of a Bunsen burner; exercise proper laboratory safety when using the Bunsen burner.
Teacher Preparation
Teachers should prepare:
- 3 M hydrochloric acid (HCl)
Tip: Concentrated HCl (36%) is 11.65 M. To make 100 mL 3 M HCl, add 25.8 mL concentrated HCl to de-ionized water. Remember to always add acid to water. - 0.1 M aqueous solution of copper (II) chloride (CuCl₂ FW = 134.45 g/mol)
Tip: To prepare 100 mL of 0.1 M aqueous solution of copper (II) chloride, dissolve 1.34 g CuCl₂ in 100 mL of water. - 0.1 M aqueous solution of copper (II) sulfate (CuSO₄ FW = 159.61 g/mol)
Tip: To prepare 100 mL of 0.1 M aqueous solution of copper (II) sulfate, dissolve 1.60 g CuSO₄ in 100 mL of water. - 0.1 M aqueous solution of potassium carbonate (K₂CO₃ FW = 138.21 g/mol)
Tip: To prepare 100 mL of 0.1 M aqueous solution of potassium carbonate, dissolve 1.38 g K₂CO₃ in 100 mL of water. - 0.1 M aqueous solution of calcium chloride (CaCl₂ FW = 110.98 g/mol)
Tip: To prepare 100 mL of 0.1 M aqueous solution of calcium chloride, dissolve 1.11 g CaCl₂ in 100 mL of water. - Potato catalase: Cut a potato into small pieces (about 6-cm cubes; this does not have to be exact).
Keys for Success
Explain to the students that today they will be exploring reactions through a series of labs. Chemists developing products or procedures in the lab constantly have to evaluate reactions and decide which ones will meet a specific need. The students will be evaluating reactions and looking at them through the perspective of green chemistry.
Procedure
- Introduce the students to the topic of types of chemical reactions. This video may be helpful:
- Familiarize students with the concept of green chemistry. This video may be helpful:
- Hand out the Student Pre-Lab Worksheet and ask students to complete questions 1–4. You can have them do their own research in order to evaluate the "greenness," or you can use the Supplemental Information sheet and the Principles of Green Chemistry sheet.
- In the Supplemental Information sheet, you may wish to add molecular formulas. They are not included in the sheet as written, in case you wish to have students derive the molecular formula from the name of each compound.
- For question #5, you will need to give them the Student Lab Worksheet. In this question, the students will be looking at the set of experiments in the main procedure for this lab and choosing between two reaction procedures. Again, you can have them do their own research to determine the safety and "greenness," or you can give them the Supplemental Information sheet. After they come to a conclusion, have a discussion with them to determine which reaction they will do. The intention of this lab is that only one of the two reactions in each of the sections will be done.
- The materials list on the Student Lab Sheet includes materials for each procedure option presented for all four types of reactions. The teacher materials list, however, includes only the materials for the safer, "greener" procedure. This is meant to prevent students from assuming which procedures they will do based on their given materials. Again, it is intended that the teacher only prepare the materials needed for the safer, "greener" procedure options for each reaction type.
- Put students into lab groups of 2–3 and have them perform the 4 experiments that they have chosen. Ask students to fill out the corresponding observation table for each experiment on the Student Lab Worksheet. Have students answer the questions on the Student Lab Worksheet upon completion of the reactions.
- For Reaction Type C, we use potato as a source of catalase. You may also use yeast—commonly used to discuss enzymes in biology experiments—or beef or chicken liver for a more dramatic reaction.
Disposal Information
- All solutions should be collected for hazardous waste disposal. Potato pieces should be removed and disposed in solid waste.
Assessment
Collect and review the Student Pre-lab and Student Lab worksheets from each student. An answer key is available.
