Identifying Common Electrolytes and Comparing their Strengths (page 2)
Try New Approaches
- Sodium chloride (table salt) is an electrolyte (a compound that conducts an electric current in a water solution or in a molten state). Test other substances to determine whether they are electrolytes or nonelectrolytes. Repeat the experiment replacing the salt with materials such as table sugar (sucrose) and Epsom salts (magnesium sulfate).
- The number of ions in a solution is directly proportional to the conductivity of the solution; that is, the greater the number of ions, the greater the intensity of the bulb's glow. Repeat the original experiment replacing the salt with solid materials (sugar and Epsom salts) and then using solutions such as vinegar, soda, fruit juices, milk, and other liquid foods. Remove the negative end of the connected batteries and the foil from the bowl and wash with distilled water after each test Compare the electrolytic strength of each solution by comparing how intensely the bulb glows. Science Fair Hint: Display the testing materials with drawings indicating the intensity of the light produced by each testing material.
- Does the number of batteries change the intensity of the light? The energy for pushing the electric current through the filament in the bulb comes from chemical reactions in the batteries. Use a chemistry text to find out how batteries (electrochemical cells) release electrical energy. Test the effect of connecting batteries by repeating the original experiment two times, first using one battery, and then using two batteries. (Remember, do not use more than three batteries.)
Design Your Own Experiment
- Electrolysis is the process by which an electric current is used to cause a chemical change. Distilled water does not conduct an electric current, because no ions are present. The presence of a small amount of an electrolyte, such as sodium chloride, allows the solution to conduct and the electrolysis of water to take place. The products of the electrolysis of water are hydrogen and oxygen.
- Chlorine, hydrogen, and sodium hydroxide are important industrial chemicals produced by the electrolysis of brine (a concentrated solution of sodium chloride). Find out more about this process and display diagram showing the electrolyte in solution as well as the reaction at the anode and cathode. Indicate methods of separating the three chemicals.
Demonstrate the electrolysis of water by filling a drinking glass with distilled water to within 1 inch (2.54 cm) from the top. Add 14 teaspoon (1.25 ml) of table salt to the water and stir. Cut a stiff piece of paper to cover the top of the glass. Straighten the ends of two paper clips, leaving a hook on one end of each. Insert the paper clips through the stiff paper so that they are about 1 inch (2.5 cm) apart. Place the paper over the top of the glass of salty water. Prepare two aluminum foil strips as in the original experiment. Wrap one end of each strip around the hooked end of each paper clip. With your fingers, hold the free ends of the strips against the ends of a "D" cell battery. Observe the ends of the paper clips extending beneath the surface of the water (see Figure 15.2). Read about the electrolysis of water in a chemistry text to determine the chemical reactions occurring at each paper clip terminal. Use a drawing with equations indicating the changes at the cathode and anode.
- A simple battery that produces a safe amount of electric current can be made from a lemon, a steel paper clip, and a brass thumbtack. Cut the lemon in half. Stick the thumbtack and the paper clip into the pulp of one of the lemon halves. The tack and clip should be as close as possible to each other without touching. Take care not to get any lemon juice on the tops of the tack and the clip. Moisten your tongue with saliva and barely touch the tip of your tongue to the tops of the tack and the clip (see Figure 15.3). The taste sensation is due to the small amount of electric current resulting from the electrolytes in the saliva on your tongue.