How Things Work
Electric current and circuits
Conduction of Electricity in Liquids
How does conduction of electricity in liquids works? Well, we know that metals conduct electricity by the means of mobile electrons. The outermost electrons in metals are loosely held due to which they can move from atom to atom. This is why metals are excellent conductors of electricity. Liquids, on the other hand, conduct electricity by other means. Unlike in metals, the chemical bonding in liquids does not allow for electrons to move freely. This means we have to introduce charges into the water before it can start conducting. Certain compounds (ionic Compounds) dissolve in water, they do so by dissociating or breaking up their bonds. When the bond is broken, the components of the compound break apart to yield multiple constituent atoms with a charge on it. The atom loses an electron to have more protons than electrons and similarly an atom gains electrons to have more electrons than protons. This leads to a charge imbalance leading to a positive or a negative charge on the atom. The atom that becomes charged by losing or gaining one or more electrons is called an Ion. Compounds that dissociates into ions in water are called Ionic Compounds.
Ionic compounds contain charged particles called ions. For example, Sodium Chloride contains positively charged Sodium ions and negatively charged Chlorine ions. Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them. For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted. Positively charged ions move to the negative electrode during electrolysis and they receive electrons. Negatively charged ions move to the positive electrode during electrolysis and lose electrons. Both the products of the dissociation are collected at the electrodes. For example, if electricity is passed through molten sodium chloride, the sodium chloride is broken into sodium and chlorine and gets collected at the electrodes. The metals get precipitated and the gases escape. Let’s take a look at what happens in electrolysis, specifically the electrolysis of water.
Conduction of Electricity in Liquids or Electrolysis of Water
When we pass electric current or electricity in liquids, the electrolysis of water leads to the decomposition of water into oxygen and hydrogen gas.
For such electrolysis,
the electric power source is connected to two electrodes made of an inert material like platinum and these electrodes are then placed in the water. Pure water is an insulator and cannot undergo significant electrolysis without adding an electrolyte. The electrolyte increases the conduction of pure water by introducing ions into the system. The application of electric potential across the electrodes causes the water molecule to dissociate. The water molecule now becomes;
H2O = 2 H+ + OH–
The oxygen and hydrogen are oppositely charged due to which they get attracted to opposite electrodes. At the negatively charged electrode, also known as the Cathode, the hydrogen ions gain an electron to turn from positively charged hydrogen ions to hydrogen gas.
Reduction at cathode:
2 H2O →2H+(g) + 2 OH–
With the electron it receives, this reaction can be further elucidated as;
2 H+ (aq) + 2e− → H2 (g)
At the positively charged electrode, Anode, The negatively charged components of the solution travel to the other electrode (anode), give up their electrons and are transformed into neutral elements or molecules. The hydroxide ion (OH–) gives away its electron to the Anode to turn into a neutral oxygen molecule which escapes as a gas.
Oxidation at Anode:
4 H2O → 4 OH–(aq) + 4 H+
Which can be broken down to
4 OH− (aq) → O2 (g) + 2 H2O (l) + 4 e
The electrons deposited at the anode make up for the electrons taken by the hydrogen ions thereby completing the circuit. For every oxygen molecule produced at the Anode, two molecules of hydrogen gas are being created at the Cathode. Assuming equal temperature and pressure for both gases, the produced hydrogen gas has, therefore, twice the volume of the produced oxygen gas. The number of electrons pushed through the water is twice the number of generated hydrogen molecules and four times the number of generated oxygen molecules. The process of conduction of electricity in liquids or electrolysis is extremely useful to the field of electrometallurgy which means the extraction of metals through electricity. Most of the aluminium produced in this world is by the process of electrolysis or conducting electricity in liquids or some other fluids. To learn more please read the article on Electroplating
Electroplating is the process of plating one metal onto another by hydrolysis, most commonly for decorative purposes or to prevent corrosion of a metal. There are also specific types of electroplating such as copper plating, silver plating, and chromium plating. Electroplating allows manufacturers to use inexpensive metals such as steel or zinc for the majority of the product and then apply different metals on the outside to account for appearance, protection, and other properties desired for the product. The surface can be a metal or even plastic.
Sometimes finishes are solely decorative such as the products we use indoors or in a dry environment where they are unlikely to suffer from corrosion. These types of products normally have a thin layer of gold, or silver applied so that it has an attractive appeal to the consumer. Electroplating is widely used in industries such as automobiles, aeroplanes, electronics, jewellery, and toys. The overall process of electroplating uses an electrolytic cell, which consists of putting a negative charge on the metal and dipping it into a solution that contains metal salt (electrolytes) which contain positively charged metal ions. Then, due to the negative and positive charges, the two metals are attracted to each other.
The Purposes of Electroplating:
- Special surface properties
- Engineering or mechanical properties