Category Science

Humphry Davy (1778-1829) was an English chemist who conducted some early experiments using electrolysis. This process offered a way of isolating metals from the compounds in which they are naturally found. As a result, Davy discovered potassium, sodium and calcium because he was able to separate the metals into their pure form.

Humphry Davy was a pioneer in the field of electrochemistry who used electrolysis to isolate many elements from the compounds in which they occur naturally.

Davy Electrolysis is the process by which an electrolyte is altered or decomposed by applying an electric current. In addition to his isolation of sodium, potassium and other alkaline earth metals, electrolysis enabled Davy to disprove the view proposed by French chemist Antoine-Laurent Lavoisier that oxygen was an essential component of all acids. When Davy decomposed hydrochloric acid (then known as muriatic acid), he found that it consisted solely of hydrogen and chlorine.

Humphry Davy (17 December 1778 – 29 May 1829) was a Cornish chemist and inventor, who is best remembered today for isolating, by using electricity, a series of elements for the first time: potassium and sodium in 1807 and calcium, strontium, barium, magnesium and boron the following year, as well as discovering the elemental nature of chlorine and iodine. Davy also studied the forces involved in these separations, inventing the new field of electrochemistry.

In 1799, he experimented with nitrous oxide and was astonished at how it made him laugh, so he nicknamed it “laughing gas” and wrote about its potential anaesthetics properties in relieving pain during surgery. He also invented the Davy lamp and a very early form of arc lamp. He joked that his assistant Michael Faraday was his greatest discovery.

When a metal reacts with oxygen, it forms a compound called an oxide. This happens on the surface of metals such as silver. As the oxide dulls the appearance of the metal, it is often rubbed off ornaments and jewellery, but in fact this simply presents a new surface of pure metal to the air to be oxidized. However, some metals, such as aluminium, are deliberately coated, by means of electrolysis, with a layer of their oxide. This process is known as anodization. It protects the metal underneath from oxidizing further.

Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.

The anodic oxide structure originates from the aluminum substrate and is composed entirely of aluminum oxide. This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel. It has a highly ordered, porous structure that allows for secondary processes such as coloring and sealing.

Anodizing is accomplished by immersing the aluminum into an acid electrolyte bath and passing an electric current through the medium. A cathode is mounted to the inside of the anodizing tank; the aluminum acts as an anode, so that oxygen ions are released from the electrolyte to combine with the aluminum atoms at the surface of the part being anodized. Anodizing is, therefore, a matter of highly controlled oxidation the enhancement of a naturally occurring phenomenon.

Cathodes and anodes are electrodes. These are carbon or metal rods that are connected to an electric current. When they are placed in an electrolyte, current can pass through the liquid from one electrode to the other, so completing the circuit. The cathode has a negative electrical charge and the anode has a positive electrical charge. Ions in the electrolyte are being held together because they have opposite electrical charges, which attract each other. These bonds are broken because the ions with positive charges are more strongly attracted to the negative charge of the cathode than they are to the negative charge of the ions with which they are bonded. In the same way, negatively charged ions are attracted to the anode.

Cathode

When we talk about cathode in chemistry, it is said to be the electrode where reduction occurs. This is common in an electrochemical cell. Here, the cathode is negative as the electrical energy that is supplied to the cell results in the decomposition of chemical compounds. However, it can also be positive as in the case of a galvanic cell where a chemical reaction leads to the generation of electrical energy.

In addition, a cathode is said to be either hot cathode or a cold cathode. A cathode which is heated in the presence of a filament to emit electrons by thermionic emission is known as a hot cathode whereas cold cathodes are not heated by any filament. A cathode is usually flagged as “cold” if it emits more electrons compared to the ones generated by thermionic emission alone.

Anode

In the most basic form, an anode in electrochemistry is the point where an oxidation reaction occurs. Generally, at an anode, negative ions or anions due to its electrical potential tend to react and give off electrons. These electrons then move up and into the driving circuit.

If we take a galvanic cell, the anode is negative in nature and the electrons mostly move towards the external part of the circuit. In an electrolytic cell, it is again positive. Additionally, an anode can be a plate or wire having an excess positive charge.

An electrolyte is a liquid that can conduct an electric current. A metal may become an electrolyte if it is molten (melted) or dissolved in another liquid. Water can also conduct an electric current. That is why it is very dangerous to touch an electric socket with wet hands.

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons. The movement of anions and cations in opposite directions within the solution amounts to a current. This includes most soluble salts, acids, and bases. Some gases, such as hydrogen chloride, under conditions of high temperature or low pressure can also function as electrolytes. Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed “polyelectrolytes”, which contain charged functional groups. A substance that dissociates into ions in solution acquires the capacity to conduct electricity. Sodium, potassium, chloride, calcium, magnesium, and phosphate are examples of electrolytes.

In medicine, electrolyte replacement is needed when a person has prolonged vomiting or diarrhea, and as a response to strenuous athletic activity. Commercial electrolyte solutions are available, particularly for sick children (such as oral rehydration solution, Suero Oral, or Pedialyte) and athletes (sports drinks). Electrolyte monitoring is important in the treatment of anorexia and bulimia.

Some compounds can be separated into individual elements by passing an electric current through them when they are in a liquid state. This process is called electrolysis. For this to happen, the compound must be able to conduct electricity, and its elements must be held together by ionic bonds. Many industrial processes use electrolysis, especially those concerned with purifying metals or applying thin layers of metal to other objects.

Electrolysis is a way of separating a compound by passing an electric current through it; the products are the compound’s component ions. In order to predict the products of electrolysis, we first need to understand what electrolysis is and how it works. Electrolysis is a method of separating bonded elements and compounds by passing an electric current through them. It uses a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is very important commercially as a stage in the separation of elements from naturally occurring sources, such as ores, using an electrolytic cell.

• An electrolyte: a substance containing free ions, which are the carriers of electric current in the electrolyte. If the ions are not mobile, as in a solid salt, then electrolysis cannot occur.
• A direct current (DC) supply: provides the energy necessary to create or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit.
• Two electrodes: an electrical conductor that provides the physical interface between the electrical circuit providing the energy and the electrolyte.

Materials that allow electric currents to pass through them are called conductors. One of the best conductors that are fairly cheap to obtain is copper, which is why many electric cables and wires are made of this metal.

A conductor is a material which electricity, heat or sound can flow through. An electrical conductor conducts electricity. The ability to conduct electricity is called electrical conductivity.

Most metals, like iron and copper, are electrical conductors. These metals are used to make wires to carry electric current. Plasma is an excellent conductor of electricity and is used for many purposes but metals are more used. Some materials are semiconductors. This means that electricity can flow through them, but not very well. Some materials are resistors. This means that they make it very hard for electricity to flow through them.

A material that stops electric current is called an insulator (electricity). Wires are covered with insulators like plastic to stop the electricity from leaving the wire. Some materials when really cold are superconductors. They offer no resistance at all to the flow of electricity. A conductor’s resistance tends to get higher when the temperature also gets high.