Introduction
"Just do it!" You have probably heard that slogan, and there is no doubt that exercise is a key part of staying healthy. But exercising depletes the body's stores of fluids and minerals, which must be replaced. Most experts agree that if you are engaged in light to moderate exercise, drinking a glass or two of water should do the trick. But if you are exercising strenuously, you also need to replenish some of the salts that your body loses through sweat. These salts, or electrolytes, are found in most sports drinks, and also in natural juices like orange juice.
What advantages does a sports drink have over water? Water provides the liquid you need to avoid dehydration, but it does not have electrolytes. An electrolyte is a substance that will dissociate into ions in a solution. The ions in the solution give it the capacity to conduct electricity. Electrolytes, such as sodium and potassium, are present in sweat. Chloride, calcium, and phosphate ions are also electrolytes.
The proper concentration of electrolytes in your blood is essential to your health. Your cardiovascular and nervous systems—to name just two—require electrolytes to function well. Differences in the concentration of sodium and potassium inside and outside of cells allow your nerve and muscle fibers to send electrical impulses (which is how these cells communicate and get your body to react and move).
Your body keeps the concentration of the various electrolytes in its fluids within a narrow range, and this process depends on consuming enough water and electrolytes. The maintenance of electrolytes within this narrow range is due to the body's homeostatic mechanisms, which control the absorption, distribution, and excretion of water and its dissolved electrolytes.
To measure the electrolytes in this science project, you will use a multimeter. A multimeter is an electronic device that measures voltage, current, and resistance. You can learn more about these terms in the Science Buddies Electronic partners For this project, you will use just the ammeter part of the multimeter. An ammeter measures current. The procedure will describe what you need to do, but you can learn more about what a multimeter is and how to use one in the Science Buddies resource How to use multimeter
How can you use an ammeter to measure the concentration of electrolytes? You will use it to measure conductance, which is proportional to the electrolyte concentration. Because electrolytes are charged particles that carry current in solution, the conductance of the solution depends on the concentration of the electrolytes. If you increase the concentration of electrolytes in a solution, the conductance of the solution also increases. In order to measure a current in the solutions, you have to apply a voltage. You will use a 9 volt (V) battery to supply the voltage.
The symbol for conductance is G and it is measured in units called siemens (S). The symbol for current is I, and it is measured in amperes (A), commonly called amps for short. The symbol for voltage is V and it is measured in volts (also abbreviated V). Calculating the conductance is easy—it is the current divided by the voltage, as shown in Equation 1.
Equation 1.
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