CHEMISTRY NOW: Mixing the Immiscible (Grades 5-8) Print

Objective:

Students will observe the interaction of immiscible liquids by designing an experiment to test the action of surfactants. Students will compare the results of adding various surfactants to a mixture of immiscible liquids. Students will use their data and observations to discuss why some liquids are immiscible in other liquids. Students will understand how surfactants work.


Introduction Notes:

 

CHEMISTRY NOW: Mixing the Immiscible

 

 

 

Title:

 

 

Mixing the Immiscible

 

Subject/Topic:

 

 

Soap, Surfactants

 

Grades:

 

 

5-8

 

Standards

Alignment:

 

 

Physical Science: Properties, changes of properties in matter: 5-8

Science and Technology: 5-8

Science as Inquiry: 5-8

 

 

Time Allowance:

 

 

1 hour

 

 

Overview and Purpose / Objective(s)

(information, concepts to be learned):

 

  1. Students will observe the interaction of immiscible liquids by designing an experiment to test the action of surfactants.
  2. Students will compare the results of adding various surfactants to a mixture of immiscible liquids.
  3. Students will use their data and observations to discuss why some liquids are immiscible in other liquids. 
  4. Students will understand how surfactants work.

 

 

VOCABULARY:

immiscible- when two or more substances will not mix together to form a homogeneous mixture

surfactant- a wetting agent, a substance that reduces the surface tension of a liquid and allows immiscible liquids to form a homogeneous mixture

sodium laurel sulfate (SLS) – a cleaning agent in soap (surfactant)

 

Materials:

 

-          Safety goggles

-          Small clear, plastic bottles with screw tops (soda or water bottles)

-          Water

-          Vegetable oil

-          Food coloring

-          Various substances to test such as:

                                                              i.      borax solution

                                                              ii.     hand soap solution

                                                              iii.    laundry detergent solution

                                                              iv.   ammonia solution

                                                             v.    dish detergent solution

-          Large test tubes with stoppers to fit

-          Test tube rack

-          Droppers or pipettes

-          Colored pencils

 

ACTIVITY / ENGAGEMENT

(reinforcing lesson, making real-world connection)

 

Part 1

 

1. Begin by having each group of students assemble a “wave bottle” and investigate the characteristics of two immiscible liquids.

2. How to make a “wave bottle”:

a)      Obtain a small, clear, plastic bottle with a screw top.

b)      Fill it half full with water; add vegetable oil until almost full to the top.

c)      Add a few drops of food coloring to the bottle.

d)     Screw the cap on tightly.

e)      Shake the “wave bottle” and observe.

3. Have students investigate these two immiscible liquids and record observations.

4. Discuss what the students have observed. Begin with some leading questions and then follow up:

         Where did the food coloring end up?

         What does this tell you about the food coloring’s properties?

         Why does the food coloring end up in only one of the liquids?

         Why do the liquids not mix?

         What happens when you shake the bottle vigorously?

         How can we get the two liquids to mix?

 

5. Introduce surfactants and briefly explain what these substances do. Surfactants are emulsifying agents that will allow two immiscible liquids to mix. Soaps and detergents are common surfactants. Many cleaning products are surfactants and this is one of the reasons they are so good at cleaning clothing and surfaces.

 

 
   

 

 

 

 

 

 

 

 

 

 


Thanks to ITACAnet.org

 

  1. Discuss with students how they can design a valid experiment that allows them to investigate how surfactants work and what they do to our two immiscible liquids. Begin with a leading question and follow-up:

 

         How does soap work?

         What kind of investigation can we do to observe the reaction of different surfactants with water and oil?

         Can you think of other ways to get these two liquids to mix?

 

Part 2

 

Tell students that for this part of the lesson they will be designing an experiment to help them understand how surfactants work.

 

Note:  Lab safety equipment should be used, and safety protocols followed. Goggles should be worn at all times. Caution students about working with vegetable oil – although it is not a dangerous liquid, it will leave grease stains on their clothing and it is hard to clean up if spilled. Some detergents and soaps can be skin irritants, especially if students have sensitive skin.

 

Let students know they will be given 6 large test tubes with stoppers. Each test tube will have 5 mL of water and 5 mL of vegetable oil. Have the following available for the students:

 

food coloring

borax solution

hand solution

dish detergent solution soap solution

laundry detergent solution

ammonia

 

1. Ask the students to create an experiment in which they will be testing the effectiveness of substances as surfactants. Be sure that the students (in groups or working individually) write the experiment down on the included data sheets BEFORE conducting the experiment.

2. Discuss their experimental design as a class.  Did they include a control? Did they use good experimental design?

 

 

Concluding Activities:

 

After the students have finished their investigations, students should be able to describe how the surfactants affected the immiscible liquid mixture. Discuss with students the properties of these surfactants and why these substances are used as cleaners. How might these properties be useful in cleaning laundry for example?

 

 

Extension Activities:

 

1. Students may also want to investigate other ways to get the liquids to mix, like heating or vigorous shaking.

2. They might also investigate some common household substances such as baking soda, flour, salt and sugar, since immiscible liquids are often mixed during cooking.

3. Students might want to learn to make their own soap. There are many online resources available (links below).

4. Students might investigate how surfactants are helpful in cleaning up after oil spills (see link below).

5. Students might investigate other cleaning products to evaluate their surfactant characteristics.

 

Additional Resources:

         http://www.flinnsci.com/Sections/Safety/safety.asp

         http://dictionary.reference.com/browse/immiscible

         http://scifun.chem.wisc.edu/HomeExpts/layeredliquids.htm

         http://dwb.unl.edu/chemistry/labs/LABS12c.html

         http://www.newton.dep.anl.gov/askasci/chem00/chem00600.htm

         http://chemistry.about.com/od/cleanerchemistry/a/how-soap-cleans.htm

         http://www.sintef.no/static/ch/environment/lab/Oil-spill.htm

 

 

 

 

Student Worksheet for “Mixing the Immiscible”

 

 

Experiment Title: ________________Date: _______Name: __________________

 

Student Hypothesis: __________________________________________________

 

Materials:

-          Safety goggles

-          Small clear, plastic bottles with screw tops (soda or water bottles)

-          Water

-          Vegetable oil

-          Food coloring

-          Various substances to test such as:

                                                              i.      borax solution

                                                             ii.     hand soap solution

                                                            iii.    laundry detergent solution

                                                            iv .   ammonia solution

                                                             v.     dish detergent solution

-          Large test tubes with stoppers to fit

-          Test tube rack

-          Droppers or pipettes

-          Colored pencils

 

Safety Precautions:

 

________________________________________________________________

 

________________________________________________________________

 

Procedure: 

 

Wear Safety Goggles for all lab work.

1. ___________________________________________________________

2. ___________________________________________________________

3. ___________________________________________________________

4. ___________________________________________________________

5. ___________________________________________________________

6. ___________________________________________________________

7. ___________________________________________________________

8. ___________________________________________________________

9. ___________________________________________________________

10. __________________________________________________________

 

Data and Observations:

 

 

 

 

 

 

 

 

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