What is Chemical Effects of Electric Current Class 8 Notes Explained

Introduction to Chemical Effects of Electric Current

Electric current is the flow of electric charge through a conductor. In Class 8 Science, the chapter on chemical effects of electric current explains how this flow can cause chemical changes in certain liquids called electrolytes. When electric current passes through an electrolyte, it can break down the compound into simpler substances. This process is called electrolysis.

Understanding this concept is important for your NCERT exams, as it links electricity with chemical reactions. The chemical effects of electric current have many practical applications, such as in electroplating, purification of metals, and manufacturing chemicals.

What is Electrolysis? Definition and Explanation

Electrolysis is the chemical decomposition of a compound caused by passing an electric current through it. The compound must be in a molten or dissolved (aqueous) state to conduct electricity.

Key points about electrolysis:

• It requires two electrodes: anode (positive) and cathode (negative).
• The electrolyte is the substance that undergoes decomposition.
• Positive ions move towards the cathode to gain electrons (reduction).
• Negative ions move towards the anode to lose electrons (oxidation).

For example, when molten sodium chloride (NaCl) undergoes electrolysis, it breaks down into sodium metal and chlorine gas:

$$\text{2NaCl (molten)} \rightarrow 2Na (metal) + Cl_2 (gas)$$

This process helps us understand how electric current causes chemical changes.

Electrodes and Their Roles in Chemical Effects

Electrodes are conductors that allow electric current to enter or leave the electrolyte during electrolysis. There are two types:

• Anode: The positive electrode where oxidation occurs (loss of electrons).
• Cathode: The negative electrode where reduction occurs (gain of electrons).

The nature of the electrodes and the electrolyte affects the products formed. For example, in the electrolysis of water, the electrodes are usually inert (like platinum or graphite) to avoid reacting with the products.

Example: Electrolysis of water produces hydrogen gas at the cathode and oxygen gas at the anode:

$$2H_2O (l) \rightarrow 2H_2 (g) + O_2 (g)$$

This shows the chemical effect of electric current clearly.

Applications of Chemical Effects of Electric Current

The chemical effects of electric current are widely used in industries and daily life. Some important applications include:

• Electroplating: Coating a metal object with a thin layer of another metal to prevent rust or improve appearance.
• Purification of metals: Removing impurities from metals like copper.
• Extraction of metals: Obtaining pure metals from their ores.
• Manufacturing chemicals: Producing substances like chlorine and sodium hydroxide.

These applications show how the chapter's concepts are useful beyond the classroom.

Comparison: Physical Effects vs Chemical Effects of Electric Current

It is important to distinguish between the physical and chemical effects of electric current. Here's a comparison table:

This comparison helps clarify the unique characteristics of chemical effects.

Solved Example: Calculating Charge Passed During Electrolysis

Example:

If a current of 2 amperes flows through an electrolyte for 3 minutes, calculate the total charge passed.

Solution:

Charge ($Q$) is calculated by the formula:

$$Q = I \times t$$

Where:

• $I$ = current in amperes = 2 A
• $t$ = time in seconds = 3 minutes = 3 \times 60 = 180 s

So,

$$Q = 2 \times 180 = 360 \text{ coulombs}$$

This charge causes the chemical changes during electrolysis.