Whose Mouth is Cleaner – Yours or a Dog’s?

Some people will argue that a dog’s mouth is cleaner than a human’s. We decided to test that theory with Test Assured’s 4 Test Kit Set for Schools and Science Fairs. Our test will compare water samples that have been in contact with human mouths and dog’s mouths. The Test Assured set includes 4 test kits for analyzing your samples and is appropriate for children in grades three through twelve.

Supplies

The first thing you need to do is gather your supplies:

• Test Assured 4 Test Kit Set with TD Meter
• 4 different water samples
• Measuring cup
• Zipper sandwich bags
• Paper towels

Preparation

To prepare for the tests, you’ll need to gather your water samples.  For this experiment, you need four different water samples.  The first one should be a control sample.  Since the water we drink and give to our dog is filtered, we used filtered water as our control.  If you normally drink tap water and give tap water to your dog, tap water should be your control sample. Our second sample was from our dog’s water bowl.  Our next sample came from a public water fountain.  The final sample needed to more closely mimic the sample from the dog bowl, so we gargled a mouthful of water and collected that for our fourth sample.

 

 These are the four samples we’ll be testing:

1. Control sample (either tap water or filtered water)
2. Water from a pet dish
3. Water from a public water fountain
4. Gargled water

We found that one of the easiest ways to handle water samples is to use zipper sandwich bags.  You can easily label the bags, and they are large enough to allow for the TDS test.  For more stability (and less chance of spills) you can put the baggies inside mugs or cups.

Now is a good time to label your vials and write your water sources in the results notebook.

Note: We tested water from our dog’s bowl, but this experiment could be done with water from a cat bowl, fish bowl, or hamster bottle.

 

 Testing

The first test you want to start with is for total dissolved solids, using the TDS meter.  The meter will not fit in the test vials, so it is easier to complete this part of the experiment while your samples are still in larger containers.  To perform the TDS test, simply turn on the meter and submerge the prongs in the samples. Rinse the meter with clean water between each test. Record your results in the results notebook.

After completing the TDS test, you will need to pour your samples into the vials you labeled.  To transfer your samples to the vials, simply snip off a small corner of the baggie to create a spout. Fill each vial to within a ¼” of the top.  Be sure to wipe up any spills, so you don’t contaminate the test strips.

Before you get started with the tests, now is a good time to make some visual observations. Take notes about how clear or cloudy your samples look.  Some of your samples may be cloudier than the others.  Some of the samples could contain dirt or food particles. These observations can be written in the “Notes” on the last page of the results notebook.

Now you’re ready to get started with the rest of the tests. It’s best to work with one sample at a time.  Follow these instructions to complete the remaining tests.

 

 

Alkalinity/pH/Hardness Test

1. Remove the test strip from the packet labeled, “ALK/pH/Hard”
2. Pick up the strip on the end with no pads
3. Dip the strip in the sample for one second and remove
4. Hold the test strip level and wait 10 seconds
5. Place the strip as shown in the picture and compare to the color chart for alkalinity, pH, and hardness
6. Record your results in the results notebook

Total Chlorine/Copper/Nitrate/Nitrite Test

1. Remove the test strip from the packet labeled, “CL/CO/NA/NI”
2. Pick up the strip on the end with no pads
3. Dip the strip in the sample three times and remove – DO NOT SHAKE OFF EXCESS WATER
4. Hold the test strip level for 2 seconds
5. Place the strip as shown in the picture and compare to the color chart for chlorine and copper
6. Wait 45 seconds before reading the results for nitrate and nitrite
7. Record your results in the results notebook

Iron Test (Complete this test last)

1. Remove one iron reagent tablet from the foil packet and place in test vial (the reagent could alter the results of other tests which is why the iron test is completed last)
2. Place the cap on the test vial and shake for approximately one minute, until the tablet is completely dissolved
3. Remove the test strip from the packet labeled, “Iron Test”
4. Dip the strip in the sample for 2 seconds
5. Shake the strip once and wait 60 seconds
6. Place the strip as shown in the picture and compare to the color chart for iron
7. Record your results in the results notebook

 Repeat all three tests for each of your samples.

Results

Now that you have completed each of the four tests on your four samples, it’s time to look at your results.  Ask yourself these questions:

• Which tests showed the most variation across all samples?
• Did any of the test results exceed the EPA recommended levels for drinking water? (These are listed in the Guide & Results Notebook.)
• What results did you find the most surprising?
• Whose mouth do you think is cleaner?

Record your answers on the “Notes” page.  If you are using this as a science fair project, you can use clear tape to fix the test sticks to the color charts to display your results.