Conductivity of Liquids

• Electric current can produce chemical changes
• Some liquids conduct electricity while others do not
• Most liquids that conduct electricity are solutions of acids, bases, and salts

Conductivity of Liquids

• Materials that allow electric current to pass through them are good conductors
• Materials that do not allow electric current to pass through them easily are insulators
• To test whether a liquid conducts electricity, a tester can be used
• The tester consists of a battery, wires, and a bulb
• When the free ends of the tester are dipped into a liquid, the circuit is complete if the bulb glows
• If the bulb does not glow, it indicates that the liquid is a poor conductor or an insulator
• LED (Light Emitting Diode) can also be used in place of a bulb
• An LED glows even when a weak electric current flows through it
• LEDs have two leads: a longer lead (positive) and a shorter lead (negative)
• The conduction of electricity through liquids allows for various applications, such as electroplating

Chemical Effects of Electric Current

• When an electric current passes through a conducting solution, it causes chemical reactions
• These chemical reactions are known as chemical effects of electric current
• Examples of chemical effects:
• Formation of bubbles of gas on the electrodes
• Deposition of metal on electrodes
• Change of color of the solution

Electrolysis of Water

• When an electric current is passed through acidified water, water decomposes into hydrogen and oxygen
• Hydrogen is collected at the cathode (negative electrode)
• Oxygen is collected at the anode (positive electrode)
• The chemical reaction can be represented as: 2H₂O (l) → 2H₂ (g) + O₂ (g)
• Sulfuric acid is added to water to make it a better conductor

Electroplating

• Electroplating is a process of depositing a thin layer of a desired metal on another material by means of electricity
• Applications of electroplating include:
• Chromium plating on car parts, bath taps, kitchen gas burners, bicycle handlebars, and wheel rims for a shiny appearance and to prevent corrosion
• Iron is electroplated with zinc to prevent corrosion and rust
• Tin plating on iron is used for storing food, as tin is less reactive than iron
• Gold and silver are used for making jewelry
• The setup for electroplating typically consists of:
• An electrolyte (a solution containing ions of the metal to be deposited)
• An anode (positive electrode) made of the metal to be deposited
• A cathode (negative electrode) made of the object to be plated
• Process of electroplating:
• The object to be electroplated is first cleaned to remove dirt and grease
• It is then connected to the cathode of the electrolytic cell
• The anode is made of the metal that is to be deposited
• The electrolyte is a solution of a salt of the metal to be deposited
• When an electric current is passed through the solution, metal ions from the electrolyte are deposited on the cathode, forming a thin layer of the metal
• Example: To electroplate an iron spoon with copper:
• The iron spoon is made the cathode
• A copper plate is made the anode
• Copper sulfate solution is used as the electrolyte
• Copper from the copper sulfate solution is deposited on the iron spoon

Applications of Chemical Effects of Electric Current

• Extraction of Metals
• Used in the extraction of certain metals from their ores
• Purification of Metals
• Used in refining metals to obtain them in a pure form
• Electrotyping
• Used in the printing industry to prepare printing blocks
• Electrolytic Capacitors
• Used in the manufacturing of electrolytic capacitors for electronic circuits
• Rust Prevention
• Coating iron items with zinc can prevent rusting
• Decorative Coatings
• Coating cheaper metals with precious metals makes them more valuable and attractive