What is Chemical Effects of Electric Current Class 8: NCERT Science Explained

Introduction to Chemical Effects of Electric Current

Electric current is the flow of electric charge through a conductor. While we often study its heating and magnetic effects, the chemical effects are equally important. In Class 8 NCERT Science, the chemical effects of electric current explain how electricity can cause substances to undergo chemical changes. This happens mainly in liquids called electrolytes, which conduct electricity by the movement of ions.

When electric current passes through an electrolyte, it causes the chemical compounds to break down into simpler substances. This process is called electrolysis. Understanding this helps us learn about batteries, electroplating, and many industrial applications.

What is Electrolysis? Basic Concept and Examples

Electrolysis is the chemical decomposition of a compound caused by passing an electric current through it. It usually occurs in liquids that conduct electricity, such as molten salts or aqueous solutions.

Example:

• When electric current passes through water containing a little acid or salt, it breaks down into hydrogen and oxygen gases.

Electrolysis of Water:

• At the cathode (negative electrode), hydrogen gas is released.
• At the anode (positive electrode), oxygen gas is released.

This experiment shows the chemical effects of electric current clearly. Electrolysis is used in industries to extract metals like aluminium from their ores and to purify metals.

Electroplating: Using Chemical Effects to Coat Metals

Electroplating is a practical application of the chemical effects of electric current. It involves coating a metal object with a thin layer of another metal using electrolysis. This improves appearance, prevents rusting, and increases durability.

How Electroplating Works:

• The object to be plated acts as the cathode.
• The metal to coat with acts as the anode.
• Both are placed in an electrolyte solution containing metal ions.

Example:

• Silver plating of spoons
• Chromium plating of car parts

This process protects metals from corrosion and enhances their look, making it important in daily life and industries.

Comparison of Effects of Electric Current

Electric current produces three main effects: heating, magnetic, and chemical. Here is a comparison:

Class 8 NCERT focuses on the chemical effects to explain how electricity can bring chemical transformations, which are useful in many applications.

Key Experiments Demonstrating Chemical Effects in Class 8

Several simple experiments help students understand the chemical effects of electric current:

• Electrolysis of water: Passing current through water to produce hydrogen and oxygen gases.
• Electroplating: Coating a metal spoon with a thin layer of silver.
• Decomposition of copper sulphate solution: Passing current through copper sulphate solution to deposit copper on the cathode.

These experiments show how electric current causes chemical changes and help build a strong conceptual foundation for Class 8 students.

Formula and Concept: Calculating Electrolysis Quantities

The amount of substance deposited or liberated during electrolysis depends on the quantity of electric charge passed through the electrolyte.

The relationship is given by Faraday's laws of electrolysis:

$$ m = Z imes Q $$

Where:

• $m$ = mass of substance deposited (in grams)
• $Z$ = electrochemical equivalent of the substance
• $Q$ = total electric charge passed (in coulombs)

Since $Q = I imes t$ (current × time), we can calculate the mass deposited if current and time are known.

Worked Example: If a current of 2 A is passed through a copper sulphate solution for 30 minutes, find the mass of copper deposited. (Electrochemical equivalent of copper = 0.000329 g/C)

Solution:

• $Q = I imes t = 2 imes (30 imes 60) = 3600$ C
• $m = Z imes Q = 0.000329 imes 3600 = 1.1844$ g

So, 1.1844 grams of copper will be deposited.