Fat: Who Says? (Measuring Obesity) What’s Your Resistance?
The Relationship Between Resistance and Concentration of Ions(C)
Student Data Page 3C Part 3
Problem Statement:Does the concentration of ions affect the resistance of a solution?
Activity Background:In Part 2 of this activity, you learned about ions in solution and about electrolytes in theblood. Remember that when table salt (NaCl) dissolved in water, it produced ions that were able to conduct electricity. You also learned that butter (which is a fat with the samedensity of yellow fat in the human body) acts as an insulator and therefore does not conduct electricity.
When considering the human body, electrolyte is a medical term that describes the positively and negatively charged particles in the body. For example, your body fluids —blood, plasma, interstitial fluid (fluid between cells) — are like seawater and have a highconcentration of sodium chloride (table salt, or NaCl). The balance of electrolytes is impor-tant in allowing our bodies to function normally. A severe imbalance of electrolytes is a medical emergency.
Activity Instructions:Part 1:1. Using your multimeter, set the dial to measure resistance.
2. Using the procedure you learned in previous activities, make sure the meter is functioning properly by touching the two probes together.
3. Identify Variables in the Experiment: Write the independent variable and the dependent variable for this part of the investigation and list some constants that would be importantin controlling the experiment.
Hint: The independent variable is the manipulated variable. That means the variable (factor) that you are changing. In other words, what is different between test groups? The independent variable in an experiment is the variable chosen by the experimenter and it is manipulated or changed by the experimenter.
The dependent variable is also called the responding variable or outcome variable. It may change in response to the independent variable being tested. The dependent variable is measured for the effect the independent variable has on it. Identify the independent and dependent variables in this experiment.
Constants are things that are the same with each of the items you are testing. In order to have a controlled experiment, all variables except the independent and dependent variables must be controlled. This is done by making sure that they are the same for all test groups. These are called constants in an experiment. List 3 variables that are made constant in this experiment.
List 3 variables that are kept constant in this experiment. a. ________________________________________________________b. ________________________________________________________c. ________________________________________________________
4. Hypothesis: Write a hypothesis based upon the background that predicts how the independent variable may affect the dependent variable. Be sure to write the hypothesis as an “if, then” statement._____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
5. Create a data table in which you can record the relationship between Concentration of Ions of the solution and the Resistance (Ω) of the solution. You will take 2 measurements for each concentration of salt and find the average. You will test 8 concentrations.
6. Fill the cup with distilled water. Place the multimeter electrodes as far apart as possible inthe solution. Measure the resistance and record in a data table of your own design. Repeat a second time for accuracy.
7. Add 1/2 teaspoon of kosher salt and mix the solution. Repeat step 6 again with the new solution.
8. Repeat step 7 increasing the amount of salt by 1/2 teaspoon until the readings are not changing – take at least 8 readings.
9. Graph your results by making a line graph of salt concentration vs. resistance. Be sure to include a title, axis labels, and units of measurement.
______________________________ (Axis label)
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(Axi
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Title _______________________________________________________
