NCERT Solutions Class 8th Science Chapter – 11 Chemical Effects of Electric Current
Chapter – 11
Chemical Effects of Electric Current
Notes
Water – A Conductor or Insulator The water that we get from taps, hand pumps, wells, and ponds is not pure but a solution. A small number of mineral salts are naturally present in it. This water is thus a conductor of electricity. On the other hand, distilled water is free of salts, and thus an insulator.
Chemical Effects of Electric Current – The passage of an electric current through a conducting solution causes a chemical reaction. The resulting effects are called chemical effects of current. Electroplating is an example of a chemical effect of current.
Applications of Electroplating – Electroplating is a very useful process. It is widely used for coating many metal objects and parts with a thin layer of a different metal.
Electrode – It is the metallic rod/conductor through which electricity enters or leaves an electrolyte.
Electroplating – The process of depositing a layer of any desired metal on another metallic object, by means of electricity, is called electroplating.
Good Conductors – The materials that allow the electric current to pass through them, are conductors of electricity. For example: Metals such as copper, aluminium.
LED – These are Light Emitting Diodes that contain two wires called leads. One lead slightly longer is always connected to the positive terminal of battery while the other lead is connected to the negative terminal of the battery.
Poor Conductors or Insulators – The materials, which do not allow an electric current to pass through them easily, are insulators. For example Rubber, plastic and wood.
Tester – A tester is a piece of electrical equipment used to check the presence of electric current. It is usually a conductor with a led/bulb to indicate that the current is present in the circuit.
Electrodes and electrolyte
A conductor, when immersed in a solution with its end connected to the terminals of a battery, thereby completing a circuit, is called an electrode. There are usually two electrodes→ cathode (ve) and anode (+ve).
An electrolyte is a solution in which the electrodes are submerged. They dissociate on the passage of electric current.
The electrodes, electrolyte and battery together form the electrochemical/electrolytic cell.
Applications of Electroplating
Coating zinc on the iron to prevent corrosion and rust.
Coating silver and gold for jewellery.
Coating tin onto iron for cans as tin is less reactive than iron.
Chromium coating for car parts, and bath fittings as it has a shiny appearance.
Conducting Liquid
Liquids conduct electricity too, when there are salts dissolved in the liquid.
Most liquids that conduct electricity are solutions of acids, bases or salts.
Acids, bases and salts
Acids and bases are chemical substances that dissociate to form ions when dissolved in a solution. They are a good conductor of electricity because of the presence of the ions.
Salts, when dissolved in water, also conduct as they release positive/negatively charged ions.
Conduction of electricity in the water
Distilled water is a bad conductor of electricity because of the absence of dissolved salts and minerals.
Water starts conducting when acids, bases or salts are dissolved that release ions, which conduct when a potential difference is applied.
Electric circuit
A closed-loop path which a current take, is known as an electric circuit.
When the path of the circuit is closed, the current flows through it, but when there is a break in the path (switch is open) then, the circuit is open and is not conducting.
