Author(s): Thompson, T. Garner / Date Created / Revised: May 31, 2016
Six Weeks Period: 5th / Grade Level & Course: 10th & 11th Chemistry
Timeline: 8 days / Unit Title:Solutions / Lesson #1
Stated Objectives:
TEK # and SE / C.10 Science concepts. The student understands and can apply the factors that influence the behavior of solutions. The student is expected to:
C.10A Describe the unique role of water in chemical and biological systems.
Supporting Standard
C.10E Distinguish between types of solutions such as electrolytes and nonelectrolytes and unsaturated, saturated, and supersaturated solutions.
Readiness Standard
Scientific Process TEKS
C.2 Scientific processes. The student uses scientific methods to solve investigative questions. The student is expected to:
C.2I Communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphs, journals, summaries, oral reports, and technology-based reports.
See Instructional Focus Document (IFD) for TEK Specificity
Key Understandings / · A solution is composed of a solvent and one or more solutes in a homogenous mixture.
— What is a solute? What is a solvent?
· Water plays a unique role in chemical and biological systems.
— What are the properties of water that make it unique and an important solvent?
— How is water important in chemical systems?
— How is water important for life?
· There are several ways to describe aqueous solutions.
— How are different types of solutions describe
Misconceptions / Students may think substances are either soluble or not soluble in water.
Students may think there is only one way to describe the concentration of a solution. Students may think of solutions as only made up of solids in water.
Key Vocabulary /
· solute
· solvent
· electrolyte / · nonelectrolyte
· dilute
· concentrated / · saturated
· unsaturated
· supersaturated
Suggested Day
5E Model / Instructional Procedures
(Engage, Explore, Explain, Extend/Elaborate, Evaluate) / Materials, Resources, Notes
Advance Preparation
/ 1. Refer to the MSDS sheets for safety and disposal information of chemicals.2. Prior to Day 1:
· Prepare samples of vegetable oil and detergent in labeled dropper bottles.
· Obtain small rubber bands that will float on water in a petri dish. Try the investigationprior to classto be sure your rubber bands will sink in the investigation.
· Optional: Arrange for access to student computers/Internet for research.
3. Prior to Day 2:
· Prepare the following for theDescribing Solutionsdemonstrations:
o 4–500 mL beakers, half full of tap water, and labeled 1, 2, 3, and 4
o Sodium chloride: 4 samples of 1g, 5g, 10g, 20g
o Supersaturated sodium acetate solution:
§ Place 75 g of sodium acetate in a 250 mL beaker, and add 50 mL of water. (The solubility of sodium acetate is 170 g/100 mL at 100°C.)
§ Heat the beaker gently on the hot plate, and stir constantly until the sodium acetate is completely dissolved. Make sure that all crystals are dissolved. Add a few more mL of water, if necessary, to dissolve all crystals.
§ Remove the beaker from the heat, and cover it with aluminum foil.
§ Allow the solution to cool undisturbed. The solution must be completely cool before using.
§ If the solution crystallizes, add a few mL of water, reheat, and cool again.
4. Prior to Day 3:
· Prepare sets of solutions and chemicals in small, labeled dropper bottles for each group or lab table to share (Electrolytes and Non-Electrolytes).
· Obtain conductivity meters that will allow you to differentiate samples of tap, distilled, and de-ionized water. Test the solid, molten ionic, and molecular substances as well. Ensure you have batteries for the conductivity meters. Note: If you do not have enough materials, youcould perform the testing as a demonstration.
· If available, consider using probeware (conductivity sensors). You will then need to modify the equipment and materials provided to students.
· Decide how you want to have students share their results. For example, you may wish to prepare class data tables for each period on chart tablet.
5. Prior to Day 4, determine your guidelines for the Performance Indicator. It may be helpful to create an example or two for students to be able to visualize your requirements.
6. Note: Begin to collect labels and/or bottles from commercial products that will be used in the upcomingLesson 02, Day 1to show concentrations. Consider asking students to bring in examples from home. / · aluminum foil (1 roll for demonstration)
· beakers (250 mL, 2 for demonstration)
· beakers (see Advance Preparation, 4 - 500 mL, half full of tap water, labeled 1, 2, 3, and 4 for demonstration)
· conductivity tester (1 per group)
· distilled water
· dropper bottle of liquid detergent (1 per group)
· dropper bottle of vegetable oil (1 per group)
· graduated cylinder (1 for demonstration)
· hot plate (1 for demonstration)
· markers (per group)
· molecular model set (per group)
· paper (large, such as poster boards, construction paper, etc., 1 per student)
· Petri dish (top or bottom, 1 per group)
· rubber band (1 per group)
· safety goggles (1 for teacher)
· safety goggles (1 per student)
· sodium acetate (crystals for demonstration)
· sodium chloride (see Advance Preparation, 4 samples - 1 g, 5 g, 10 g, 20 g)
· stirring rod (1 for demonstration)
· stirring rod or spoon (1 for demonstration)
· supersaturated sodium acetate solution (see Advance Preparation, per demonstration)
· well plates (12 per group)
· filled dropper bottles (see Advance Preparation, labeled, per group)
· 0.1 M NaCl
· 0.1 M Ca(OH)2
· 0.1 M NaHCO3
· 0.1 M acetic acid
· 0.1 M hydrochloric acid
· dilute household ammonia solution
· dilute sucrose solution
· rubbing alcohol
· vegetable oil
· de-ionized or distilled water
· tap water
Day 1 and 2
Engage / 1. Dividethe classinto groups of 2–4. Instruct students to write their observations in their science notebooks after each step. Explain that at the end of the activity, they will discuss their observations.
2. Distribute materials to each group.
3. Project the following, and instruct students to respond to the following questions in their science notebooks:
· What do you think will happen when you place a rubber band in the petri dish and add water?
· What change do you think will occur if vegetable oil is added to the water and rubber band?
· What do you think will then happen if you place a drop of detergent placed on the oil?
4. Instruct students to fill the Petri dish half full with distilled water. Then, carefully place their rubber band on the water so it “floats.”
5. After the rubber band is in place, instruct students to carefully add two drops of vegetable oil onto the area of the water that is enclosed by the rubber band. Ask students to observe what happens.
6. Instruct students to place a drop of detergent onto the center of the oil layer (inside the rubber band) and observe what happens.
7. Ask students to dispose of the materials appropriately and set up for the next period or group.
8. Project the following questions, and ask students to discuss in their groups:
· How can you explain the rubber band “floating” on the water?Accept all answers at this time.
· What happened to the rubber band shape when you added the oil? Why? Accept all answers at this time.
· What happened to the rubber band shape when you added the detergent? Why?Accept all answers at this time.
9. Monitor student group discussions to record any possible misconceptions. Remind groups about the polar nature of water molecules, if necessary.
· Note: Water molecules sticking together –cohesion– creates surface tension. The rubber band should take on a circular shape when the oil is added because the surface tension of the surrounding water, pulling the rubber band outward, is not balanced by the surface tension of the oil. Adding detergent to the oil then causes the oil to begin to dissolve, changing the surface tension, and thus, the shape of the rubber band.
10. Facilitate a discussion in which student groups summarize their observations and explanations. If students do not address surface tension, guide the discussion in this area.
11. Allow students several minutes to summarize their answers in their science notebooks. Remind them to use complete sentences.
12. Use a partner sharing strategy to continue the discussion by asking students to brainstorm other unique properties of water. Ask partners to record the properties in their science notebooks.
13. Provide an opportunity for students to share their ideas with the rest of the class. Record all ideas for reference as students continue the unit and look for similarities. Additionally, begin to sort student ideas into categories to relate to the properties of water. /
Materials:
· Petri dish (top or bottom, 1 per group)· rubber band (1 per group)
· distilled water (per group)
· dropper bottle of vegetable oil (1 per group)
· dropper bottle of liquid detergent (1 per group)
Instructional Notes:
This activity may also be conducted as a demonstration with a projection system.
Consider sharing and review of video demonstrations or illustrations of water surface tension.
Check For Understanding:
Use student discussions and reflections as opportunities for formative assessment.Science Notebooks:
Students write observations of the rubber band in the water before oil is added, after oil is added, and after detergent is added.Day 3 and 4
Engage/Explore / 1. Continue to facilitate the discussion of the importance and properties of water. Instruct students to take notes in their science notebooks.
2. Purposefully, connect earlier concepts from Unit 04 to the properties of water studied in this unit (See the Instructional Notes and Background Information sections.).
3. Distribute molecular model sets, and instruct students to build a water molecule. Ask students to draw the representation in their notebooks.
4. Askstudents to respond to the following prompts in their science notebooks:
· Draw the Lewis electron dot structure for water.
· Explain how polarity in a water molecule is established.
5. Remind students to use complete sentences and academic vocabulary in their responses. Some words to include are valence electrons, octet, polar, nonpolar, electronegativity, atom, bent, linear, trigonal planar, and tetrahedral.
6. Discuss the following:
· What is the molecular shape of water?Bent
· How is polarity related to the geometric shape of the molecule?If the geometrical shape is unbalanced when there are polar bonds, then the molecule will be polar.
7. Focusing on water as a solvent, ask students to explainsolvent, solute,andsolution. Guide the discussion as needed.
Ask:
· What is a solute?A solute is a substance being dissolved to make a solution.
· What is a solvent?A solvent is the substance in which a solute is dissolved to make a solution.
8. Ask students to reflect on the role or importance of water in chemical and biological systems.
9. Include the following questions and others based on student discussions in the Engageactivity:
· How can an insect walk on the surface of a pond?
· What are some effects related to ice floating in water?
· How does water in a plant move from its roots to leaves?
· How does the high percentage of water in blood contribute to the role of blood in the body?
· How do fish “breathe?”Answers will vary based upon discussion.
10. Use the following questions in summarizing student ideas from the discussion.
· How is water important for life?Thechemical processes of life all happen in cells in aqueous solution because of water’s unique properties
· How is water important in chemical systems?When water is the solvent for a reaction, the reaction is said to occur in anaqueous solution.
· What are the properties of water that make it unique and an important solvent?Answers will vary, but include: water molecules are polar and dissolve polar and ionic compounds, and other properties of water that impact Earth processes (e.g., weather, erosion) include its high surface tension, high heat capacity, and density as a solid, less than as a liquid.
11. Optional -Assign individual students or teams to research and share other examples of the importance of water, especially in biological systems. Provide research materials and/or access to student computers/Internet (see Advance Preparation). Alternatively, you may wish to assign this activity for homework. /
Materials:
· molecular model set (per group)Instructional Notes:
Background connections to prior concepts in Unit 04:
Covalent bond: bond in which one or more pairs of electrons are shared by two atoms. Sharing may be equal, such as between two of the same atoms, or unequal, sharing between two different atoms. Unequal sharing results in a polar bond, depending on the differences in the electronegativities of the two atoms. The polarity of the bond will be more negative toward the more electronegative atom.
The polarity of bonds in conjunction with the molecular structure determines whether a molecule is polar or not. Water, H2O, is a polar molecule; for example. It is not linear, but bent due to oxygen’s two pairs of unshared electrons. Since each O-H bond is polar (negative toward the O), the H2O molecule is polar as well.
Science Notebooks:
Students record notes on the properties of water and the importance of water in biological and chemical systems
Day 4 and 5 Explore/Explain / 1. Ask students to recall the Classification of Matter unit in which they studied mixtures and pure substances.
Pose the following question:
· Is a solution a heterogeneous or a homogeneous mixture? Why? Homogeneous because it is the same throughout
2. Explain to students that they will need to understand some concepts related to solutions and will be constructing definitions for related terms.
3. Writer or project the wordssolvent,solute,concentrated,anddilute.
4. Show students the samples of solid NaCl and the labeled beakers of tap water (see Advance Preparation).
5. Pour each NaCl sample into the appropriate beaker. Stir each until all the salt is dissolved.