How Effective is Your Detergent?
Author(s): Arleni Lopez and Ron Hitchcock
Instrumentation - Teacher's Guide
SED 695B
Overview: Students will test several brands of detergents that they bring from home, to determine their relative effectiveness .They will vary the concentration, pH, and temperature for a provided brand of detergent to determine the optimal conditions to get the cleanest laundry

Materials
 

Topics:

Enzyme activity, macromolecules, catalysts, pH, temperature, detergent

Experiment Summary

1. Four cleaners/detergents were testes.

Oxiclean, Members Mark, Surf, Ariel

2. Their effectiveness was determined by how much gelatin was degraded over a period of 24 hours.

3. We found that Ariel was the most effective, next was Member's Mark. Surf and OxiClean were not effective at degrading proteins.

4. After completing this part of the experiment. We tested one detergent (Ariel) and altered the temperature of the water to find its optimal performance. The temperature of the water solutions was: 30. 6 C, 56.1 C, and 13.3 C.

5. We found that that Ariel works best in mild tap water conditions. It does works in cold water but not as good. We also found that proteases in the detergent are work the least in hot temperature. It seems that hot temperature denatures them.

Thus if you are washing clothes using detergent with enzymes, do not use hot water. Hot water will inactivate you proteases.

 

Standards:

Cell Biology

1.b.Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.

Genetics

5. c. Students know how genetic engineering (biotechnology) is used to produce novel biomedical and agricultural products.


 

Results

Ingredients: Ingredients: Ingredients: Ingredients:

Measuring height of gelatin

 

 

Level of gelatin

Prepare the gelatin one day before the lab. Add about 15 ml of gelatin into test tube.

Gelatin with detergent solution

 

 

Preparing the detergent solution

250 ml of water and 5 ml of detergent. Mix for two minutes

Ariel

amount degraded: 3 mm

Member's Mark

amount degraded: 2 mm

OxiClean

amount degraded: 0 mm

 

Surf

amount degraded: 0 mm

 

DATA Table

 

Ariel Tap (30.6 C)

Amount degraded: 3mm

Ariel Hot ( 56.1 C)

Amount degraded: 1mm

Ariel cold ( 13.3 C)

Amount degraded: 2 mm


Procedure for Students: (see student hand out)

1. Obtain a test tube that is half filled with gelatin.
2. Measure the height of the gelatin from the bottom of the tube to the top surface of the gelatin in millimeters.
Record your data in Table 3.
Using a Chinese marker draw a line at the level of the gelatin.
3. Prepare your detergent solution as follows:
a. Measure 5 ml of detergent using the beaker. Leave the detergent in the beaker.
b. Run the cold tap water for 15 seconds
c. Then measure 250 ml of water and add it into the beaker with the detergent.
d. Mix the solution for two minutes.
4. Add 5 ml of your detergent solution to the test tube with gelatin.
5. Label your test tube with your initials and period and place it in the rack so that it sits in vertical position. Allow the test tube to set undisturbed at room temperature for approximately 24 hours.
6. Repeat steps 1-4 with a second gelatin-filled test tube. However, use Wool Lite to prepare your solution and label the test tube "control".
7. Make sure you have completed Data Table 1.
8. After 24 hours, make observations and record in Table 2. Then measure the height of the gelatin from the bottom of the tube to the top surface of the gelatin in millimeters. Record this in Data Table 3.
9. Write down your results in the Class data table on the chalkboard. Then record the results of all other lab groups and record in Data Table 4.

 

Questions: (link to student work sheet)

1. Make a bar graph of your results from Data Table 4. Be sure to label and title your graph. If the same detergent was tested by more than one group, graph the average only.
2. Which detergent(s) was most effective in degrading the gelatin as compared to the control group?
3. Was the control detergent able to degrade the gelatin?
4. Did the control group do better than some of the other detergents?
5. Which detergent cost the least per load?
6. Which detergent cost the most per load?
7. Was the most expensive detergent the best at degrading the gelatin? Explain.
8. Was the cheapest detergent the worst at degrading the gelatin? Explain.
9. Taking into account the cost and the effectiveness of the detergent, which detergent would be the most economical to buy?
10. Would the protease enzyme in the detergent be effective in cleaning all stains? Explain.
11. Predict what would happen to the enzymes in the detergent if you changed the temperature of the water? Would the protease be as effective if you prepared your solution in hot water or freezing water?
12. Predict what would happen if you changed the pH of water. The pH of water is 7, neutral. Do you think the detergent would be as effective? Explain.
13. Some fruits like pineapple contain enzymes similar to the protease's found in detergents. Explain why gelatin recipes tell you not to add pine apple when making gelatin? What would happen if you did?
14. Find out what other fruits contain protease enzymes.
15. Knowing this about pineapple, could you remove a stain by rubbing pineapple on it? Explain.

Applications to everyday life:

Pineapple can not be added to gelatin because it contains similar protease enzymes found in detergents that would not allow the gelatin to set.

Every-day curiosities can be answered though this lab such as:

  • Do the cheap Mexican/Latin detergents really work better than American brands?
  • High efficiency detergents, do they work better than regular detergents?
  • Are powder detergents better than liquid detergents.

 

From P&G Website
Description / questions
Description / questions

Teacher Preparation

1. Prepare the gelatin as directed by the box on day in advance. This is for four of the Knox envelopes.

  • 2 cups of boiling water to dissolve gelatin powder.
  • 2 cups of cold water.
    4 cups of water equals to 946.3 milliliters.

2. Fill each test tube with 15 ml (or half way) prepared gelatin. You can add less if you would like.
3. Four envelopes of Knox are enough for 63 test tubes.
4. You don't necessarily need a refrigerator, if you reduce the amount of water, the gelatin will set at room temperature. It would also help if you cranked up the air conditioner.


Teacher Tips

1. Remind students to hold the test tube from the top. If they hold it at the bottom where the gelatin is at, their body heat might melt it.

2. Jello brand gelatin can be used instead of Knox. Colored gelatin makes it easier to see when measuring the level (height) of gelatin.

3. For more dramatic results you may choose to increase the time from 24 hours to 48 hours. The viscosity of the gelatin will affect your results. The more viscous the less the gelatin will degrade. However, if the gelatin is too soft the detergent will disintegrate all the gelatin and you will have un conclusive results

 

Limit the number and type of detergents


1. Although this lab asks that each student bring their own detergent from home, it would be better to limit the number of detergents testes. This way you end up with multiple tests for each detergent brand within the class and across classes which makes for better and easier data analysis.
2. To limit the variables ask students to bring non-concentrated liquid or power detergents. If you would like to control it even further, ask them to bring only either powder or liquid detergents.

 

Saving resources


1. If you don't have enough gelatin or test tubes for each students to have two test tubes, one for the control and one for their detergent. I would pair students up. It's extremely likely that some students will not bring their detergent. Thus pair up those students without their own detergent with one student that did bring their detergent.
2. Because you will need to purchase Wool Lite or Surf yourself, you can reduce the amount used and the cost by not having each group do a control test tube. You yourself can prepare one "control" test tube for each class, which students will use as a reference.


Answering Questions


If students ask what about lipid stains?


  • Detergents contain synthetic, organic surface-active agents called surfactants, which lower the surface tension of water and allow dirt and grease on clothing to be removed.

  • Lipase - is an enzyme that breaks down lipid stains. But Lipase enzymes break down too easily in washing machines to be very useful in detergents. However, their stability is being studied and further developed through methods such as genetic screening and modification.


What about carbohydrates stains?

  • Detergents also contain other enzymes called amylases for starch removal.
Description / questions
Description / questions
   

References & Links:

1. About Detergents

2. Lab - Do detergents containing enzymes really perform better than those lacking enzymes?

3. P&G products

4. Student work sheet

5.Wikipedia - difference between soap and a detergent