7th grade science project ideas


Science Fair Project: Do Liquids Conduct Electricity? Is One Liquid a Better Conductor than Another Liquid?

Benjamin Franklin is very well known for many things, one of which is his experiments with electricity. Now you can conduct your own experiments and see which liquids are better conductors of electricity.

To define electric current it is a flow of electrical charge. When a metal conducts electricity, the charge is carried by electrons moving through the metal. Electrons are subatomic particles with a negative electrical charge. When a solution conducts electricity, the charge is carried by ions moving through the solution. Ions are atoms or small groups of atoms that have an electrical charge. Some ions have a negative charge and some have a positive charge.

There are very few ions in water so it does not conduct electricity very well. When table salt is dissolved in water, the solution conducts very well, because the solution contains ions. The ions come from the table salt, whose chemical name is sodium chloride. Sodium chloride contains sodium ions, which have a positive charge, and chloride ions, which have a negative charge. Because sodium chloride is made up of ions, it is called an ionic substance.

You will not find ions in all substances. Some are mode of uncharged particles called molecules. Sugar is such a substance. When sugar is dissolved in water, the solution does not conduct electricity, because there are no ions in the solution.

Some substances that are made of molecules form solutions that do conduct electricity. Ammonia is such a substance. When ammonia dissolves in water, it reacts with the water and forms a few ions. This is why laundry ammonia, which is a solution of ammonia in water, conducts electricity, but not very well.

Oftentimes when two different solutions are mixed, the substances they contain react with each other and form ions. This is what happens when ammonia and vinegar are mixed. An ammonia solution contains only a few ions, and it conducts electricity only poorly. A vinegar solution also contains only a few ions and conducts only a little electricity. But when these solutions are mixed, the ammonia reacts with the acid in vinegar (acetic acid), and they form a lot of ions. This is why the mixture of ammonia and vinegar conducts electricity very well. To do this science fair project you will need a buzzer or a multimeter than will sound off. You will also need craft sticks, tin foil, a V9 battery, masking tape, cups, salt water and other liquids to test such as soda, orange juice, milk or others.

To begin this science fair project you must cover your sticks with tin foil. Take the red wire of your buzzer and attach it with masking tape to the positive end of your battery. Look for the plus sign on the battery. If you wish you can purchase an analog multi meter which will measure the resistance of the liquids being tested. Take the black wire of the buzzer and attach it with masking tape to one of the foil-covered craft sticks. Tape it down really good. If the wire pulls away from the stick, the experiment will not work.

Take another craft stick and tape it to the negative electrode on the battery. Be certain the tin foil stays in contact with the negative end of the battery. Test your tester by touching the two sticks together. You will hear a buzz. The buzz may make you jump a little. Test the salt water. Dip the two ends of your tester into the salt water. Leave a small gap between the sticks of one to two inches. If the buzzer buzzes, you are conducting electricity. Test other Liquids. The salt in the water dissolves into ions which, in turn, conduct electricity. The more salt in the water, the louder your buzzer will buzz. Soda and many drinks contain sodium and will therefore buzz. Although nobody got shocked with the tester, you still want to handle your creation with care.

READ ON for more information on this "electrifying" project.



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