Fat: Who Says?
Measuring Obesity by Bioelectrical
Impedance Analysis
Circuitous Adventures-Conductors and Insulators
Student Information Page 3C Part C
Activity Introduction:
So which materials can conduct electricity and which ones cannot? That’s what you will find
out as you complete this activity.
Activity Background:
An electrical conductor is a material that allows electrical current to flow freely. An electrical
insulator is a substance that does not allow electrical current to flow freely. A homogeneous
solution is composed of one or more substances dissolved in another substance; such that
the original substances are no longer distinguishable. An example of a homogenous solution
would be salt water because the salt breaks apart into ions when salt is placed in water. A
heterogeneous mixture consists of visibly different substances combined. An example would
be sugar water, because the sugar will eventually separate at the bottom of the glass as it
“falls out” of solution. The human body is quite complex and made of many different materials; some of these are be conductors, while others are insulators; some are homogeneous and
some are heterogeneous.
The human body has many electrolytes, which are positively and negatively charged
particles (ions) that form when salts dissolve and separate (dissociate) in water. Electrolyte
balance is important to the normal functioning of cells, nerves, muscles, blood pressure, and
glands. When electrolytes become unbalanced, as in excessive sweating, vomiting, diarrhea,
or serious burns and wounds, they need to be replaced. With severe electrolyte loss, life
threatening conditions can arise.
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3C, PART C
Corpulosity
Why are some materials conductors and others non-conductors? Metals allow
the free movement of electrons and thus are able to carry an electrical current.
What about non-metals that are conductors? We need to look at something
called ions. Ions are electrically charged elements because they have either gained or lost
electrons. When compounds such as acids, bases, and salts are dissolved in water, ions are
formed. Acids, bases, and salts are ionic compounds, which dissolve in water to produce both
positive and negative ions called electrolytes. Non-ionic compounds do not break into ions
when dissolved in water; sugar is an example.
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Activity Materials:
(per group or station)
Dry Materials:
• 1 Toothpick
• 1 Rubber band
• 1 Cotton ball
• 1 Small piece paper towel
• 3 metal wires, each made of different metal
• Battery
• Buzzer or bulb
• 1 piece of lead (graphite) from the center of a pencil*
Wet Materials:
• 5 plastic cups labeled and 1/2 filled with distilled water, tap water, sugar water,
salt water, and butter
• 1 Copy Student Information Page
• 1 Copy Student Data Page
• Paper towels or baby wipes with which to clean up.
* Woodless Graphite sticks can be used instead of pencil leads
(These can be found in the drawing sections at craft stores such as Hobby Lobby. They are
approximately 6 mm thick and 15 cm long. A sharp knife can be used to scrape off a thin coating
along the 15 cm length)
Activity Instructions:
1. Gather your materials. Be sure your get five cups - You will need one for distilled
water, tap water, sugar water, salt water, and butter.
2. Set up the simple circuit as you have used in previous parts of this activity. Create a
break between the switch and the buzzer, see Figure 1.
Bulb or Buzzer
Testing the Materials
Between the Break
Cotton Ball
Break in Circuit
Battery
Battery
Bulb
Figure 1 Creating a Break in the Circuit
3. Before you actually test each of the materials, on your own paper, create a
data table that has a column in which you predict whether that material will
conduct electricity and one to record if it actually did conduct electricity.
There are 14 different materials to test.
LESSON
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
3
ACTIVITY 3C, PART C
Corpulosity
Break in the Circuit
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4. Using the dry materials first, place one item across the break so that each
exposed wires from the circuit touch one end of the object. See Figure 1.
Repeat this step for all other dry materials.
Remember: If you hear the buzzer or see the bulb light up, then that
material has completed the circuit and that material conducts electricity.
5. Saving the butter for last, test the liquid materials next. Put both ends of
the broken circuit into the cup and submerge them in the liquid.
Make sure the two exposed metal ends of the circuit are NOT touching each
other in the liquids.
Be sure to dry off the ends BEFORE placing them in the next cup you
are testing.
6. Record all your results in the chart and indicate if the buzzer sounded.
7. Now mix the salt water with the sugar water. Create a new row on your chart (14th
item). Predict if this mixture will conduct electricity. Test your new mixture and record
these results in your chart.
Processing Out:
Conductors
Non-conductors
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Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3C, PART C
Corpulosity
1. Make a T-chart and list all the conductors you found on one side of the chart and all
the non-conductors (insulators) on the other.
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2. Were your predictions correct? Which were not correct?
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3. The salt water is a homogeneous solution. Define the word homogenous.
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4. When mixed, sugar water and salt water forms a heterogeneous mixture. Define the
word heterogeneous.
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5. How does the conductivity of this new heterogeneous mixture compare to the
conductivity of each of the liquids separately?
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6. Using the background information included in this activity, explain why salt water
conducts electricity and sugar water does not?
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8. How does this relate to your body and electrical flow?
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Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3C, PART C
Corpulosity
7. Why do you think that the combination of salt and sugar waters conducted
electricity?
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