Glossary with Definitions:
Conductor:
Definition: A material that allows electricity to pass through it easily. Most metals are good conductors of electricity.
Insulator:
Definition: A material that does not allow electricity to pass through it easily. Examples include plastic, wood, and bakelite.
Continuity Tester:
Definition: A device used to check whether a material conducts electricity. It typically consists of a bulb or LED connected to a battery using connecting wires.
Electrolyte:
Definition: A substance that conducts electricity when dissolved in water or when in a molten state, as it breaks into free mobile ions.
Electrolysis:
Definition: The process in which an electric current passes through an electrolyte, causing chemical changes, like the decomposition of a compound into its ions.
Strong Electrolyte:
Definition: An electrolyte that completely dissociates into free ions when dissolved in water. Examples include sodium chloride and sulfuric acid.
Weak Electrolyte:
Definition: An electrolyte that partially dissociates into free ions when dissolved in water. Examples include acetic acid and ammonium hydroxide.
Non-electrolyte:
Definition: A substance that does not dissociate into ions when dissolved in water, thus not allowing electricity to pass through. Examples include distilled water and alcohol.
Voltaic Cell:
Definition: A device that converts chemical energy into electrical energy. It consists of two different metals (electrodes) immersed in an electrolyte solution, creating an electric current.
Electrode:
Definition: A conductor through which electricity enters or leaves a medium, typically used in electrolysis or in a voltaic cell. Common types are the anode and cathode.
Anode:
Definition: The electrode at which oxidation occurs, often marked as the positive terminal in electrochemical cells.
Cathode:
Definition: The electrode at which reduction occurs, often marked as the negative terminal in electrochemical cells.
Electromagnetic Induction:
Definition: The process by which an electric current is induced in a conductor by a changing magnetic field, discovered by Michael Faraday.
Induced e.m.f. (electromotive force):
Definition: The voltage generated by electromagnetic induction when a conductor moves through a magnetic field or when the magnetic field around a conductor changes.
Electroplating:
Definition: The process of depositing a thin layer of metal onto an object using electrolysis, often used to improve appearance or prevent corrosion.
Electrorefining:
Definition: The process of purifying a metal by electrolysis, where impure metal is used as the anode and pure metal is deposited at the cathode.
Chemical Effects of Electric Current:
Definition: The changes in the chemical composition of a solution or compound that occur when an electric current passes through it, a phenomenon known as electrolysis.
Ions:
Definition: Atoms or molecules that have gained or lost electrons, giving them a net electric charge. Positive ions are called cations, and negative ions are called anions.
Magnetism:
Definition: A force exerted by magnets when they attract or repel other materials. The magnetic field is produced by moving electric charges.
Faraday’s Laws of Electrolysis:
Definition: Two fundamental laws that describe the relationship between the amount of substance altered at an electrode during electrolysis and the quantity of electricity passed through the electrolyte.
Electromagnetic Field:
Definition: A physical field produced by moving electric charges, which affects the behavior of charged objects in the vicinity of the field.
Battery:
Definition: A device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy.
Current:
Definition: The flow of electric charge, typically measured in amperes (A), which is caused by the movement of electrons in a conductor.
Voltage:
Definition: The difference in electric potential between two points in a circuit, which drives the flow of electric current.
Magnetic Field Lines:
Definition: Invisible lines that represent the direction and strength of a magnetic field. The denser the lines, the stronger the magnetic field.
Ionization:
Definition: The process by which atoms or molecules gain or lose electrons to form ions, often in the presence of electricity or heat.
Corrosion:
Definition: The process of deterioration of metals due to chemical reactions, often involving oxygen and moisture, leading to rusting.
Conductivity:
Definition: The ability of a material to conduct electric current. Materials that easily allow the flow of electric current are called conductors.
Resistance:
Definition: The opposition to the flow of electric current, measured in ohms (Ω). High resistance means less current can flow for a given voltage.
Electromotive Force (emf):
Definition: The energy provided by a source (like a battery or generator) per charge, driving the flow of electric current through a circuit.
Acid:
Definition: A substance that releases hydrogen ions (H⁺) when dissolved in water and can increase the conductivity of a solution.
Base:
Definition: A substance that releases hydroxide ions (OH⁻) when dissolved in water and can also increase the conductivity of a solution.
Cation:
Definition: A positively charged ion, typically formed by losing electrons.
Anion:
Definition: A negatively charged ion, typically formed by gaining electrons.
Electrochemical Reaction:
Definition: A chemical reaction that involves the transfer of electrons between reactants, often occurring in electrolysis or within batteries.
Voltage Source:
Definition: A device or power supply that provides a constant potential difference (voltage) to drive electric current through a circuit.
Something To Know
A. Fill in the blanks.
- Most liquids, that conduct electricity, are solutions of____________ ____________ and ____________ .
Answer – acids, bases, and salts
- The ____________ the concentration of an ion in the solution, the greater is the conductivity of the solution.
Answer – higher
- The passage of an electric current, through a solution, can cause____________ effects.
Answer – chemical
- When electric current is passed through copper sulphate solution, copper gets deposited on the plate connected to the ____________ terminal of the battery.
Answer – negative
- The process, in which electricity is used to deposit a thin layer of any desired metal on another metallic object, is known as____________.
Answer – electroplating
- The faster is the relative motion between the magnet and the (closed) coil, the ____________ is the current that flows through the coil.
Answer – greater
B. State True or False for the following statements.
- A solution of silver nitrate is a good electrolyte.
Answer – True
- An electrolytic cell consists of a cathode, anode and an electrolyte.
Answer – True
- Oxygen gets liberated at the anode during the electrolysis of acidfied water.
Answer – True
- Electrorefining is the process of coating one metal on another using an electric current.
Answer – False
(Correct term for coating is electroplating; electrorefining is used for purification.)
- The phenomenon of ‘Electro-magnetic Induction’ was discovered by the Italian Scientist, Alessandro Volta.
Answer – False
(Correct term for coating is electroplating; electrorefining is used for purification.)
C. Tick (✓) the correct option.
- The names of four electrolytes are given below:
(A) sea water
(C) nitric acid
(B) tap water
(D) oxalic acid
Out of these, the weak electrolytes are the ones labelled as—
A and B
B and C
B and D
A and D
Answer – B and D
- Electrolytes conduct electricity due to the movement of—
the electrolyte itself.
positive as well as negative ions.
electrons only.
the electrodes themselves.
Answer – positive as well as negative ions.
- The electrode, connected to the positive terminal of a battery, is known as the—
anode
cathode
positive pole
electrorefiner
Answer – anode
- The phenomenon of decomposition of an electrolyte, when electricity is passed through it, is known as—
conduction
electrolysis
coating
electrorefining
Answer – electrolysis
- The process, of coating of (say) iron with chromium, is known as—
extraction
electroplating
electrolysis
electrorefining
Answer – electroplating
D. Answer the following questions in brief:
- State the appropriate term, used for a liquid or solution, which can conduct electricity (along with some accompanying chemical changes).
Answer – Electrolyte
- Distinguish between strong and weak electrolytes. Give two examples of each.
Answer – Strong electrolytes: These are substances that completely dissociate into ions in a solution and conduct electricity well.
Examples: Sodium chloride (NaCl), Sulfuric acid (H₂SO₄)
Weak electrolytes: These are substances that partially dissociate into ions in a solution and conduct electricity poorly.
Examples: Acetic acid (CH₃COOH), Ammonium hydroxide (NH₄OH)
- Name the device that converts—
(a) Chemical energy into electrical energy.
Answer – Battery (or Voltaic cell)
(b) Mechanical energy into electrical energy.
Answer – Generator
- Name the scientists who introduced the (scientific) world to the—
(a) voltaic cell
Answer – Alessandro Volta
(b) phenomenon of electrolysis
Answer – Michael Faraday
(c) phenomenon of electro-magnetic induction
Answer – Michael Faraday
- An Electrode ‘A’ is connected to the positive terminal while Electrode ‘B’ is connected to the
(a) Give the names of the Electrodes A and B.
Answer – Names of the Electrodes A and B
Electrode A (connected to positive terminal): Anode
Electrode B (connected to negative terminal): Cathode
(b) Name the process associated with the circuit shown here.
Answer – The process is electrolysis of water (chemical decomposition of water into hydrogen and oxygen gases using electric current).
(c) Name the gases produced at A and B.
Answer – At Anode (A): Oxygen (O₂)
At Cathode (B): Hydrogen (H₂)
- State the meaning of the terms:
(a) Electro-magnetic induction
Answer – The phenomenon in which a changing magnetic field induces an electric current in a conductor.
(b) Electrolysis
Answer – The process of using electrical energy to drive a non-spontaneous chemical reaction, typically the decomposition of compounds into their elements.
(c) Electrodes
Answer – Conductive materials through which electric current enters or leaves an electrolyte in an electrochemical cell.
(d) Electrorefining of metals
Answer – The process of purifying metals by using electrolysis, where impure metal is used as the anode and pure metal is deposited at the cathode.
- State three uses of the phenomenon of electrolysis.
Answer – lectroplating: Depositing a thin layer of metal onto another surface (e.g., gold plating, chrome plating).
Electrorefining of metals: Purifying metals like copper and silver.
Extraction of metals: Obtaining metals from their ores, such as the extraction of aluminium from bauxite.
E. Answer the following questions.
- Give reasons for the following:
(a) Solid sodium chloride does not conduct electricity while sodium chloride solution conducts.
Answer – Solid sodium chloride does not conduct electricity because its ions are fixed in a rigid structure and cannot move. In the solution, sodium chloride dissociates into sodium (Na⁺) and chloride (Cl⁻) ions, which are free to move, allowing the solution to conduct electricity.
(b) It is not safe to carry out electrical repairs outdoors during a heavy downpour.
Answer – Water is a good conductor of electricity. During a heavy downpour, the water can create a pathway for the electric current, increasing the risk of electric shock and making it unsafe to perform electrical repairs outdoors.
(c) To carry out electrolysis of water, a few drops of sulphuric acid are (carefully) added to the water.
Answer – Pure water is a poor conductor of electricity. Adding a few drops of sulfuric acid increases the ion concentration in the water, making it a better conductor and facilitating the electrolysis process.
(d) Kitchen gas burners are often coated with chromium.
Answer – Chromium coating is resistant to corrosion, heat, and wear. It makes the surface of the kitchen gas burners more durable, easy to clean, and resistant to rust or tarnish.
- Three electrolytic cells A, B and C are connected with identical bulbs in separate circuits as shown in the diagram. Electrolytic cell A contains sodium chloride solution and Electrolytic cell B contains acetic acid solution. The electrolytic cell C contains distilled water.
Justify your answers.
(a) In which Set-up will the bulb glow the brightest?
Answer – Set-Up A (Sodium Chloride Solution)
Justification:
Sodium chloride (NaCl) is a strong electrolyte that dissociates completely into Na⁺ and Cl⁻ ions in water, providing a high concentration of free ions for conduction.
More ions → higher current → brighter glow..
(b) In which Set-up will the glow of the bulb be quite dim?
Answer – Set-Up B (Acetic Acid Solution)
Justification:
Acetic acid (CH₃COOH) is a weak electrolyte that ionizes only partially in water, producing fewer H⁺ and CH₃COO⁻ ions.
Fewer ions → lower current → dimmer glow compared to Set-Up A.
(c) In which Set-up will the bulb not glow at all?
Answer – Set-Up C (Distilled Water)
Justification:
Distilled water lacks dissolved salts/ions, making it a non-electrolyte.
No free ions → no current flow → bulb remains unlit.
- Ramit sets-up the circuit shown below for purification of Copper:
(a) Name the metals used for Electrodes A and B.
Answer – Name the metals used for Electrodes A and B.
Electrode A (Anode): Impure Copper
Electrode B (Cathode): Pure Copper
Justification:
In copper purification, the impure copper rod is made the anode (A), which dissolves into the solution.
Pure copper is deposited on the cathode (B).
(b) Name the process of purification.
Answer – Electrorefining (or Electrolytic Refining) of Copper
Justification:
This process uses electrolysis to purify metals by dissolving impure metal at the anode and depositing pure metal at the cathode.
(c) Name the solution that needs to be used.
Answer – Copper Sulphate Solution (CuSO₄)
Justification:
CuSO₄ solution acts as the electrolyte, providing Cu²⁺ ions for the transfer of copper from the anode to the cathode.
- (a) Define ‘electroplating’. How can steel spoons be plated with silver? Explain with the help of a diagram.
Answer – Electroplating is a process in which a thin layer of metal is deposited onto the surface of another metal using electric current.
To plate steel spoons with silver:
The steel spoon is made the cathode (negative electrode).
A silver electrode is made the anode (positive electrode).
The spoon is immersed in a silver nitrate solution.
When the electric current is passed through the solution, silver from the anode is deposited onto the spoon’s surface.
Diagram
Anode (silver electrode)
Cathode (steel spoon)
Electrolyte (silver nitrate solution)
(b) State any three uses of electroplating.
Answer – Protection against corrosion: Items like coins or jewelry are electroplated to prevent rusting or tarnishing.
Improved appearance: Electroplating is used to give a shiny, decorative finish to objects like cutlery and watches.
Enhanced durability: Tools and machine parts are electroplated to improve wear resistance.
- Describe an experiment to show that we can get electrical energy by using a magnet.
Answer – To demonstrate the generation of electrical energy through a magnet, perform the following experiment:
Take a coil of copper wire and connect the ends to a galvanometer to detect any current.
Move a strong bar magnet rapidly in and out of the coil.
The galvanometer will show a deflection, indicating the presence of an induced current in the wire.
This shows that mechanical energy (motion of the magnet) is converted into electrical energy.
- A coil of insulated copper wire is connected to a torch bulb. State the likely ‘response’ of the bulb, if a bar magnet is—
(a) pushed into the coil?
Answer – The bulb will glow momentarily. The movement of the magnet will induce a current in the coil, causing the bulb to light up briefly.
(b) pulled out of the coil?
Answer – The bulb will glow momentarily, in the opposite direction. The removal of the magnet from the coil induces a current in the opposite direction, causing the bulb to light up.
(c) held stationery within the coil?
Answer – The bulb will not glow. No current is induced when the magnet is stationary, as current is generated only when the magnetic field is changing relative to the coil.
Value Based Question
One day, when Aisha came back from school, she was very upset and was on the verge of crying. When her mother consoled her, Aisha vent out her feelings to her and told her that she was bullied by seniors at her school. Her mother calmed her and advised her to learn to face such challenges. She gave her the example of electroplating, in which a protective cum decorative layer is put over a base metal to help it avoid corrosion. She told Aisha that we all need to develop a ‘shield of courage’ around us.
This would help us in protecting ourselves from negative influences and in ‘freeing us from fear’. Aisha resolved to follow her mother’s advice and felt better equipped to face all types of challenges.
- State the values depicted by Aisha’s mother.
Answer – Empathy and Support: Aisha’s mother listened to her concerns and comforted her in a loving and understanding way.
Encouragement and Strength: She encouraged Aisha to develop resilience and face challenges courageously, similar to how electroplating provides a shield against corrosion.
Wisdom: By using the example of electroplating, she imparted valuable life lessons about building inner strength to protect oneself from negativity.
Optimism: She helped Aisha shift her mindset from feeling helpless to feeling empowered and ready to face the challenges of life.
- State any three conditions that help in getting a smooth and firm deposit during electroplating.
Answer – Proper Current Density: The current used during electroplating must be optimal to ensure the even and uniform deposition of the metal.
Purity of Electrolyte Solution: The electrolyte solution must be free of impurities to ensure a smooth and high-quality deposition of the metal.
Proper Temperature: The temperature of the electrolyte solution must be maintained within a specific range to ensure that the metal is deposited uniformly and firmly.
- Have a ‘group discussion’ about developing qualities that can help one to face the ‘day to day challenges of life’.
Answer – A group discussion on this topic can include the following points:
Resilience: The ability to bounce back from setbacks and continue working toward goals, even when faced with obstacles.
Self-Confidence: Believing in oneself and one’s abilities helps in tackling challenges with a positive mindset.
Adaptability: The willingness to adjust to changes and learn from experiences, making it easier to handle challenges that come our way.
Time Management: Organizing tasks efficiently and managing time well can reduce stress and make it easier to handle multiple responsibilities.
Positive Thinking: Maintaining a positive attitude, even in difficult situations, helps to overcome challenges with a clear mind and a hopeful outlook.
Problem-Solving Skills: Being able to analyze problems and find effective solutions is key to overcoming everyday challenges.
Support System: Having a strong support system of friends, family, or mentors can provide guidance and encouragement when facing difficulties.
This discussion can be structured around sharing personal experiences and strategies that have helped individuals cope with life’s challenges effectively.
Something To Do
- We can make a continuity tester using the magnetic effect of current. Wrap an electric wire few times around a compass needle box. Make a simple circuit as shown. The free ends of the ‘tester’ can be put in the solution to be tested.
This type of a tester is more sensitive as compass needle shows quite a large deflection even for a weak current. Try repeating some of the activities using this tester.
Answer – To make a continuity tester, follow these steps:
Take an electric wire and wrap it a few times around a compass needle box, ensuring the wire is tightly wound and the compass needle can freely move.
Connect the ends of the wire to the circuit, with one end in the solution to be tested.
When the current passes through the solution, the magnetic field generated by the current will deflect the compass needle, indicating whether the solution is conducting electricity.
This tester is sensitive enough to detect even weak currents, making it an efficient tool for testing conductivity.
- Metal polishing substances and their related, wastes and releases, are all potential hazards to human health and the environment, when not managed properly. Many metal ‘finishing processes’, like electroplating, generate toxic or hazardous pollutants that can result in direct exposure of the employees, and/or pollution of the air, land and water. For example, chromium provides excellent corrosion resistant properties but may lead to liver, kidney, brain and muscle damage. Hence, in the electroplating factories, the disposal of the used conducting solutions is a major concern. There are specific disposal guidelines and methods to protect the environment.
Find out the health concerns, associated with the ‘waste’, in electroplating industries. How are people trying to resolve them?
Answer – The health concerns associated with waste from electroplating industries include:
Chromium exposure: Chromium, commonly used in electroplating, can be harmful when exposed to humans. Long-term exposure may lead to liver, kidney, brain, and muscle damage.
Heavy metal contamination: Other metals like cadmium, lead, and nickel can be toxic to humans and wildlife if not disposed of properly.
Water and soil pollution: Waste from the electroplating industry, if not properly treated, can contaminate water bodies and soil, posing a threat to ecosystems and public health.
Resolution efforts include:
Improved waste treatment: Electroplating industries are increasingly using advanced waste treatment methods, such as filtration and neutralization, to remove harmful chemicals before disposal.
Closed-loop systems: Some industries are adopting closed-loop systems that recycle the electrolytes, minimizing waste generation.
Safer alternatives: Research into less toxic alternatives to chromium and other hazardous chemicals is ongoing to reduce health and environmental risks.
- Take out the carbon rods carefully from two discarded (discharged) cells. Use them as two electrodes to test the conduction of electricity through various liquids.
Answer – Once the carbon rods are carefully removed from discarded cells, they can be used as electrodes for testing the conduction of electricity through different liquids.
Connect the rods to a power source and place them in various liquids, such as saltwater, vinegar, and tap water, to observe if electricity passes through the solution. The flow of electricity will depend on the conductivity of the liquid tested. For example, saltwater will conduct electricity, while pure water will not.
- Some of us might have a ‘generator’ fitted in our bicycle. See how the cycle bulb lights up more brightly when the cycle is ‘pedalled’ at a faster rate.
Answer – A generator on a bicycle works by converting mechanical energy (from pedaling) into electrical energy, which powers the bicycle’s light.
When the bicycle is pedaled faster, the generator rotates more quickly, producing more electricity. This results in a brighter light as the current increases. The faster the pedaling speed, the more electrical energy is generated, lighting the bulb more brightly.
- Solve the ‘crossword puzzle’ with the help of the given clues.
Across
1.Coating a thin film on another material using electricity.
- The name given to the negative electrode.
- A conducting liquid.
- The name given to the positive electrode.
Down
- A chemical effect of current.
- ‘Atoms’ that have an electric charge.
- An expensive metal, often coated on ornaments.
- A rod, through which an electric current enters or leaves a circuit, having a ‘liquid solution’ as one of its parts.
Answer – Across
Electroplating (Coating a thin film on another material using electricity)
Cathode (The name given to the negative electrode)
Electrolyte (A conducting liquid)
Anode (The name given to the positive electrode)
Down
Electrolysis (A chemical effect of current)
Ions (Atoms that have an electric charge)
Gold (An expensive metal, often coated on ornaments)
Electrode (A rod, through which an electric current enters or leaves a circuit, having a ‘liquid solution’ as one of its parts)
Additional Questions and Answers – 01
Short Answer Questions:
Questions – What is the role of an electrolyte in electrolysis?
Answer: An electrolyte is a conducting solution that allows the flow of ions, which is necessary for the electrolysis process. It helps in carrying electric current between the two electrodes during electrolysis.
Questions – Why does the bulb glow when current passes through a conductor?
Answer: The bulb glows because the electric current flows through the filament in the bulb, causing it to heat up. As it heats up, the filament emits light, which is observed as the glow of the bulb.
Questions – What is the difference between conductors and insulators?
Answer: Conductors are materials that allow the flow of electric current (e.g., metals like copper, aluminum). Insulators are materials that do not allow the flow of electric current (e.g., rubber, plastic).
Long Answer Questions:
Questions – Explain the process of electroplating with an example.
Answer: Electroplating is the process of coating a metal object with a thin layer of another metal using electric current. For example, in the electroplating of silver, the object to be plated (say a spoon) is connected to the cathode, while a silver electrode is connected to the anode. When current passes through the electrolyte solution (which contains silver salts), silver ions from the anode get reduced and deposit as a thin layer over the spoon. The electroplating process is used to improve the appearance and resistance to corrosion of the object.
Questions – Describe the working of a simple electric motor.
Answer: A simple electric motor consists of a coil of wire placed between the poles of a magnet. When current flows through the coil, it generates a magnetic field around it. The interaction between the magnetic field of the coil and the magnet causes the coil to rotate. This is due to the force exerted on the current-carrying coil by the magnetic field. The rotation continues as long as the current flows, and this movement is used to perform mechanical work, like rotating a fan or a machine.
Questions – What is the significance of the safety precautions in using electrical devices?
Answer: Electrical devices can pose serious hazards if not used properly. Safety precautions, such as using insulated wires, grounding electrical appliances, and installing circuit breakers, help prevent electrical shocks, fires, and other accidents. It is crucial to follow these precautions to ensure safe handling of electrical devices and protect individuals from harm.
Multiple Choice Questions (MCQs):
Questions – Which of the following is the best conductor of electricity?
- a) Plastic
- b) Copper
- c) Wood
- d) Rubber
Answer: b) Copper
Questions – In an electrolytic cell, the anode is always: a) Negative
- b) Positive
- c) Neutral
- d) Dependent on the electrolyte
Answer: b) Positive
Questions – What happens when electric current passes through a conducting solution?
- a) It generates heat
- b) It produces light
- c) It causes a chemical reaction
- d) It causes magnetism
Answer: c) It causes a chemical reaction
Questions – Which of the following is NOT a property of conductors?
- a) Allow electric current to pass
- b) Have high resistance
- c) Have free electrons
- d) Are usually metals
Answer: b) Have high resistance
Questions – Which metal is commonly used for electroplating gold jewelry?
- a) Copper
- b) Zinc
- c) Silver
- d) Nickel
Answer: d) Nickel
True or False Questions:
Questions – A solution of sodium chloride in water is a good conductor of electricity.
Answer: True
Questions – Electric current flows from the negative terminal to the positive terminal in a circuit.
Answer: False (Current flows from positive to negative.)
Questions – The process of electroplating is used to coat metals with plastic to increase their strength.
Answer: False (Electroplating coats metals with a thin layer of another metal, not plastic.)
Questions – An electric current can only flow through metallic conductors.
Answer: False (An electric current can also flow through electrolytes and other conductive materials.)
Questions – In electroplating, the object to be plated is connected to the positive terminal.
Answer: False (The object to be plated is connected to the negative terminal of the power source.)
Additional Questions
Questions – What is the purpose of using a salt bridge in an electrochemical cell?
Answer: A salt bridge is used to complete the circuit in an electrochemical cell. It allows the flow of ions between the two half-cells, maintaining the electrical neutrality of the solution.
Questions – How can we increase the resistance of a conductor?
Answer: The resistance of a conductor can be increased by increasing its length, decreasing its cross-sectional area, or using a material with a higher resistivity.
Questions – What is the role of a fuse in an electrical circuit?
Answer: A fuse is a safety device that protects electrical circuits from overcurrent. It melts and breaks the circuit when the current exceeds a safe level, preventing damage to the electrical components.
Additional Questions and Answers – 02
Short Answer Questions (1-2 marks)
Questions – What is an electrolyte?
A substance that conducts electricity in molten/aqueous state and decomposes into ions during conduction (e.g., saltwater, acid solutions).
Questions – Why does distilled water not conduct electricity?
It lacks free ions; impurities or dissolved salts are needed to provide ions for conduction.
Questions – Name two strong electrolytes.
Sodium chloride (NaCl), Sulphuric acid (H₂SO₄).
Questions – What happens during electrolysis of water?
Water decomposes into hydrogen (at cathode) and oxygen (at anode) bubbles.
Questions – Define electroplating.
Depositing a thin layer of a metal (e.g., gold, chromium) on another object using electricity.
Questions – Why is electroplating done on bicycle handles?
For shiny appearance (chromium/nickel plating) and protection from rust.
Questions – What is electromagnetic induction?
Generation of electric current in a coil due to relative motion between the coil and a magnet.
Questions – Who discovered electromagnetic induction?
Michael Faraday (1831).
Questions – Why should you not handle electrical appliances with wet hands?
Tap water contains ions, making it conductive and risking electric shocks.
Questions – What is the role of graphite pencils in the electrolysis activity?
They act as electrodes (conductors for current in the liquid).
Long Answer Questions (5 marks)
Questions – Explain how liquids conduct electricity with an example.
Liquids conduct via free ions (e.g., NaCl → Na⁺ + Cl⁻ in water).
Example: Lime juice (citric acid ions) allows current, lighting a bulb.
Describe electroplating with a diagram. State its uses.
Process:
Anode: Pure metal (e.g., copper).
Cathode: Object to be plated (e.g., iron spoon).
Electrolyte: Salt solution of anode metal (e.g., CuSO₄).
Uses: Decoration (jewellery), corrosion resistance (car parts), cost-saving (gold-plated watches).
Questions – How does electromagnetic induction work? Give Faraday’s observations.
Principle: Current is induced when a magnet moves relative to a coil.
Observations:
Current flows only during motion.
Faster motion → stronger current.
Direction changes if magnet motion reverses.
Compare strong and weak electrolytes with examples.
Strong: Fully ionized (e.g., HCl, NaOH).
Weak: Partially ionized (e.g., acetic acid, tap water).
Questions – Why is Faraday’s discovery of electromagnetic induction significant?
Basis for generators (mechanical → electrical energy), enabling modern power grids.
MCQs (1 mark each)
Questions – Which liquid is the best conductor of electricity?
- a) Distilled water
- b) Vegetable oil
- c) Saltwater ✅
- d) Glycerine
Questions – Electroplating uses:
- a) Magnetic energy
- b) Chemical energy ✅
- c) Heat energy
- d) Light energy
Questions – Oxygen bubbles form at the:
- a) Cathode
- b) Anode ✅
- c) Both electrodes
- d) Nowhere
Questions – Electromagnetic induction was discovered by:
- a) Thomas Edison
- b) Michael Faraday ✅
- c) Alessandro Volta
- d) Isaac Newton
Questions – Which is NOT an electrolyte?
- a) Vinegar
- b) Lemon juice
- c) Sugar solution ✅
- d) Sea water
True/False (1 mark each)
Pure water is a good conductor. – False (No free ions).
Electroplating prevents rusting. – True (e.g., chromium plating).
Faster magnet movement increases induced current. – True.
Copper is plated on iron to make it cheaper. – False (For conductivity/decoration).
Electrolysis produces only gases. – False (Can deposit metals too).
Diagram-Based Question
Questions – Label the electroplating setup:
Anode (Copper rod)
Cathode (Iron object)
Electrolyte (CuSO₄ solution)
Battery (+ and − terminals)