CG SCERT (Chhattisgarh Board) Class 8 Science & Technology Solutions | 2026-27 Official Edition
Welcome to the complete, 100% textbook-grounded CG Board Class 8 Science Chapter 11 Solutions: Chemical Effects of Electric Current (विद्युत धारा के रासायनिक प्रभाव) in Bilingual Format (English Medium + हिंदी माध्यम). Every in-text question (Answer these / इनके उत्तर दीजिए) and end-of-chapter exercise (Exercises / अभ्यास के प्रश्न) has been solved strictly from the official 2026-27 SCERT Chhattisgarh Raipur textbook.
Activity 2 Observation Table 111
क्रसं पदार्थ चुंबकीय सुई में विक्षेप दर्शाती है…
| S.No. | Material | Compass Needle Shows Deflection (Yes / No) | Good Conductor / Poor Conductor |
|---|---|---|---|
| 2 | Distilled Water | No | Poor Conductor |
| 3 | Tap Water | Yes | Good Conductor |
| 4 | Vegetable Oil | No | Poor Conductor |
| 5 | Salt Water | Yes | Good Conductor |
| 6 | Honey | No | Poor Conductor |
| 7 | Vinegar | Yes | Good Conductor |
| 8 | Dilute Hydrochloric Acid Solution | Yes | Good Conductor |
Now Answer These Set 1
विद्युत के सुचालक और हीनचालक से आप क्या…
What do you mean by good and poor conductor of electricity?
Solid or liquid materials that allow electric current to pass through them easily are called good conductors of electricity (e.g., copper, aluminum, lemon juice, tap water). On the other hand, materials that do not allow electric current to pass through them easily are called poor conductors of electricity (e.g., rubber, plastic, distilled water, vegetable oil).
Why is distilled water a poor conductor while tap water is a good conductor of electricity?
Distilled water is completely free of dissolved salts and minerals, so it lacks free ions required to carry electric current, making it a poor conductor. In contrast, water obtained from taps, hand pumps, wells, and ponds contains small amounts of naturally dissolved mineral salts that dissociate into free ions, allowing electric current to flow easily.
Now Answer These Set 2
विद्युत धारा के रासायनिक प्रभाव से आप क्या…
What do you mean by chemical effect of electric current?
When an electric current passes through a conducting liquid (electrolyte), it causes chemical reactions and dissociates the liquid into its constituent ions. This phenomenon is called the chemical effect of electric current. Manifestations of chemical effect include
- Formation of gas bubbles at the electrodes.
- Deposition of metals on the electrodes.
- Change in color of the solution.
What are the main reasons of doing electroplating?
The main reasons for performing electroplating are
- Corrosion & Rust Protection: To protect reactive base metals like iron from rusting by coating them with corrosion-resistant metals like zinc or chromium.
- Aesthetic Appearance: To give cheap metals a shiny, smooth, and attractive finish (e.g., chromium plating on car parts and taps).
- Cost Economy: To make artificial ornaments look like expensive gold or silver at a fraction of the cost.
- Scratch Resistance: Chromium plating provides a surface that resists scratches.
- Food Preservation: Plating tin over iron cans prevents food from reacting with iron and getting spoiled.
Name some electroplated objects available in your surrounding by making a list.
- List of Electroplated Objects in Daily Life:
- Bicycle handles and wheel rims (plated with chromium).
- Bathroom water taps and showers (plated with chromium).
- Kitchen gas burners and utensils (plated with chromium/nickel).
- Artificial jewelry, chains, and rings (plated with gold or silver).
- Tin cans used for packaging food items (tin plated over iron).
- Galvanized iron roofing sheets, pipes, and bridge girders (zinc plated over iron).
Now Answer These Set 3
सरल वोल्टीय सेल में कौनसे इलेक्ट्रोड और विद्युत…
Which electrode and electrolyte is used in a simple voltaic cell?
In a simple voltaic cell
- Anode (Positive Electrode): Copper plate.
- Cathode (Negative Electrode): Zinc plate.
- Electrolyte: Dilute sulphuric acid (H_2SO4) solution kept in a glass vessel.
What is a solar cell made of?
A solar cell is made of two layers of silicon semiconductor material. The lower layer is mixed with a small trace of arsenic to form the positive layer, while the upper layer is mixed with a small trace of boron to form the negative layer.
Tick the correct answer
निम्नलिखित में से कौन विद्युत का सुचालक नहीं…
(i) Which of the following is not a good conductor of electricity:**
- Options: (a) Distilled Water (b) Lemon Juice (c) Salty Water (d) Tap Water
(a) Distilled Water
- (ii) The electrolyte used in a simple voltaic cell is:
- Options: (a) Dilute sulphuric acid (b) Dilute hydrochloric acid (c) Copper sulphate solution (d) Potassium hydroxide solution
(a) Dilute sulphuric acid
- (iii) The process of depositing a layer of any desired metal on another material by means of electricity is known as:
- Options: (a) Electrolysis (b) Electroplating (c) Chemical reaction (d) Electro refining
(b) Electroplating
- (iv) The apparatus used for electrolysis is:
- Options: (a) Electric cell (b) Voltameter (c) Ammeter (d) Magnetic needle
(b) Voltameter
- (i) Solution of …………………………………. electrolyte is used in simple voltaic cell.
Dilute sulphuric acid
- (ii) On passing current through any solution, produces ……………………. effect.
chemical
- (iii) In solar cell …………… energy is converted into …………………………… energy.
solar (or light), electrical
- (iv) Process of coating of expensive metals over cheap metals by voltaic cell is called …………..
electroplating
- (v) …………… cells are used in watches, calculator, transistors and artificial satellites.
Solar (and Button)
Answer the following questions
क्या आसुत जल विद्युत का चालन करता है…
Does distilled water conduct electricity? If not what can we do to make it a conductor?
No, distilled water does not conduct electricity because it is completely free of dissolved salts and ions. To convert it into a conductor, we can add and dissolve a few drops of an acid (such as dilute hydrochloric acid or sulphuric acid), a base (such as caustic soda / sodium hydroxide), or a pinch of common salt (sodium chloride). Dissolving these substances introduces free positive and negative ions that carry electric current through the water.
- English: In case of fire, before the fireman uses the water hose they shut off the main electrical supply for the area. Explain why they do this?
- Answer:
- English: The tap water or ground water used by firemen contains naturally dissolved mineral salts, making it a good conductor of electricity. If the main electrical supply is not turned off, high voltage electric current can travel back through the continuous stream of water to the firemen, resulting in severe or fatal electric shocks. Therefore, shutting off the main electrical supply is an essential safety precaution.
- English: Why is iron coated with zinc?
- Answer:
- English: Iron is a highly reactive structural metal that undergoes rusting and corrosion when exposed to atmospheric moisture and oxygen. Rusting weakens iron structures like bridges, automobiles, and roof sheets. Zinc is resistant to atmospheric corrosion. Depositing a protective layer of zinc over iron (a process known as galvanization) prevents iron from coming into direct contact with air and moisture, thereby halting rust formation.
- English: Explain the process of electrolysis?
- Answer:
- English:
- 1. Definition: Electrolysis is the chemical process in which a conducting solution (electrolyte) decomposes into its positive and negative ions due to the passage of an electric current.
- 2. Experimental Setup (Voltameter): The complete apparatus is called a voltameter. It consists of a glass container filled with an electrolyte and two metal rods or plates called electrodes dipped in it.
- Anode: The electrode connected to the positive terminal of the battery.
- Cathode: The electrode connected to the negative terminal of the battery.
- 3. Working Process: When the electric circuit is closed, current flows from anode to cathode in the external circuit, and inside the solution, current flows from cathode to anode. The electric current breaks down the electrolyte into cations (positive ions) and anions (negative ions). Cations move toward the cathode and gain electrons, while anions move toward the anode and lose electrons.
- 4. Balanced Chemical Reaction Example (Dissociation of Copper Sulphate Solution):
Copper Sulphate (CuSO4) → [Electric / Current] Copper Ion (Cu2+) + Sulphate Ion (SO42-)
- At Cathode (Negative Electrode):
Cu2+ + 2e^- → Cu(s) (Copper metal deposits on cathode)
- At Anode (Positive Electrode):
Cu(s) → Cu2+ + 2e^- (Copper plate dissolves to replenish solution)
- Hindi:
- English: Name the electrolyte, positive terminal and negative terminal of button cell.
- Answer:
- English: In a button cell:
- Positive Terminal (Anode): Zinc (Zn) or Aluminum (Al).
- Negative Terminal (Cathode): Silver oxide (Ag_2O) or Mercury oxide (HgO).
- Electrolyte: Paste of Sodium hydroxide (NaOH) or Potassium hydroxide (KOH) / Sodium or Potassium oxide.
- English: Write 3 uses of electroplating.
- Answer:
- English: Three major uses of electroplating are:
- Protection Against Corrosion and Rust: Iron parts of bridges, automobiles, and building materials are electroplated with zinc (galvanization) or chromium to protect them from rusting and atmospheric decay.
- Decorative & Affordable Items: Base metals are electroplated with precious metals like gold or silver to make attractive, durable, and inexpensive artificial ornaments and utensils.
- Protection of Stored Food: Iron cans used for storing food are electroplated with tin; because tin is less reactive than iron, it prevents food from spoiling due to direct contact with iron.