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Detergent Enzyme lab - Attachment 16

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					Detergent Enzyme lab - Attachment 16

Most laundry detergents today contain enzymes in order to be more effective at removing stains. The
most difficult stains are proteins and therefore, the detergents will contain a class of enzymes called
proteases. Ask students to bring in a small sample of the detergent that is used in their home. Also
ask the students to read the label and see if there is the name of an enzyme listed (usually ends with –
ase or it could be trypsin or pepsin). The variety of detergents will allow for a simple inquiry lesson to
be designed. This activity can be modified to create different levels of inquiry. Select the level at
which you are comfortable and your students will be successful. Remember to increase the levels as
the semester/year progresses in order to place more responsibility on the students. This will also
increase the level of understanding and ultimately will assess student knowledge through a
performance task.

Materials
(per group)

4 - test tubes/ bathroom sized plastic cups
1 package of gelatin
2 - 250 mL beaker
distilled water
hot plate
10% laundry detergent solution

Teacher Notes:
   1. Gelatin will serve as a source of protein.
   2. Hot plates are recommended as students will be stirring to keep the gelatin from scorching.
   3. 10% laundry detergent solution can be made by dissolving 10 grams of detergent in
      90 mL of water.



Procedures
Varying levels of inquiry

High Level:

      Groups will design experiments to determine how effective different detergents are at breaking
       down protein. Groups must submit the experimental design to the teacher prior to the start of
       the experimentation. Teacher should ensure the experiment is safe and viable (one variable, a
       control).

      Some of the designs will include:
          o Different types of detergents (cold water formulas vs. room temperature water formula,
             liquids vs. powders, different types of the same brand)
          o Temperature ( Remind students they can only change one variable therefore if they use
             temperature they must use a single detergent) … students will place a test tube in
             different temperatures … remember the gelatin will begin to “melt” at body
             temperature (39 C) …
          o pH (Remind students they can only change one variable; therefore, if they use pH they
             must use a single detergent) … students would increase/decrease pH of the detergent
      Students need to design a data table on which they will record their data. Students will conduct
       the experiment and record data. They will use their data to draw conclusions. Students need to
       be prepared to share their experimental design and results with the class. Classmates need to
       be prepared to comment on validity of experiment/conclusions and sources of error as a part of
       the formal lab report.

Medium Level:

      Groups will be assigned a one of the specific variation of the lab stated above. One group could
       serve as the control for all the other groups (they just add water to their tubes and place them
       under the same conditions as the others)
      Student Groups will complete as directed and develop all recording documents to record
       observations and data.
      Student Groups will share experiment and results with classmates. Classmates will need to
       comment on validity of conclusions and identify sources of error as a part of the formal lab
       report.

Low Level:

Prepare the Gelatin
    Add 50 mL of water to a 250 mL beaker and bring this to a boil.
    Use a balance to measure out 2 grams of gelatin on a piece of paper towel. Remember when
       you are massing something using a triple beam balance or digital balance you must take the
       mass of the paper towel into account.
    Slowly add the gelatin to the beaker of boiling water as the beaker remains on the hot plate.
       Use a stirring rod to make sure all the gelatin dissolves. Stir while the beaker is on the hot
       plate to avoid scorching the gelatin.
    Using tongs or hot mitts, remove the beaker when the entire gelatin sample is dissolved.
    Pour approximately 10 mL (divide it as evenly as possible) of gelatin in each of the four test
       tubes or bathroom size cups. Cover and allow them to cool over night.

Prepare the Detergent
    Using a balance, measure out 10 grams of powdered detergent and place it in a 250 mL beaker.
    Using a graduated cylinder and add 90 mL of distilled water to the beaker and stir until most of
       the determent dissolves.
    If the detergent is liquid, measure 10 mL of the detergent with a graduated cylinder and then
       add it to the beaker with 90 mL of distilled water.
    Label the beaker with the name of the detergent and the type of enzyme (if known).
    TEACHER NOTE: you may want to alter the pH of a couple of the detergents by splitting the
       sample and adding HCl or NaOH to mimick the protease action of the human stomach. This
       will need to be shared with the students. Groups will need to be assigned specific materials for
       this to show valid results.



Setting up the experiment
     Mark the level of the solid gelatin with a marking pencil in each of the four tubes.
     Select 3 detergents and label the test tubes with the names of the detergents to be tested.
     The fourth tube should be label as the control.
     To the control, add 15 drops of distilled water.
      Add 15 drops of the appropriate detergent to the labeled tubes and replace the cover.
      Make sure the tubes are labeled with a mark to indicate the group.
      Allow the tubes to sit for 24 hours. (TEACHER NOTE: select one of each detergent type and
       a control to be place in a refrigerator to see the different temperature makes on enzyme action.
       A group could also be placed in a very warm … not to exceed 85 degrees … optimum enzyme
       action should be body temperature but the gelatin will “melt” above 85 F) … Collect class data
       if groups manipulate different variables
      Measure the amount of liquefaction using a ruler and record in data table.
      All the tubes to sit for an additional 24 hours and record the results.

Students will complete a formal lab report. The focus of the conclusion should be on
    The purpose of the tube with water
    Which detergent was most effective (include any alterations such as temperature or pH)
    Which detergent was least effective
    Identify the enzyme even if one was not listed on the package (protease is a good response!)
    Sources of error
    Identify manipulated and responding variables
    Why detergents were effective at dissolving proteins (do we care???)
    Using data collected from the lab to explain in detail why enzymes are important to chemical
       reactions.




Teacher Notes:
   4. Gelatin will serve as a source of protein.
   5. Hot plates are recommended as students will be stirring to keep the gelatin from scorching.
   6. 10% laundry detergent solution can be made by dissolving 10 grams of detergent in
      90 mL of water.

				
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