Chemical Effects Of Electric Current Notes

Introduction

Electric current is the flow of electric charges through a conductor like a metal wire. When an electric current passes through a device or a circuit, it produces several useful effects. These effects help us operate electrical appliances in our daily life.

The main effects of electric current are:

1. Heating Effect – When current flows through a conductor, it produces heat. This effect is used in electric heaters, irons, geysers, and bulbs.
2. Magnetic Effect – Electric current produces a magnetic field around the conductor. This effect is used in electric bells, motors, and electromagnets.
3. Chemical Effect – Electric current can cause chemical changes in certain liquids. This is used for electroplating, electrolysis, and purification of metals.

Because of these effects, electricity becomes extremely useful in our homes, industries, and communication systems. Understanding these effects helps us use electrical energy safely and efficiently.In this lesson we will be mainly focussing on the chemical effects of electric current

Chemical Effect of current

When an electric current is passed through a conducting liquid such as an acid, base, or salt solution, it causes chemical changes in the liquid. This is called the chemical effect of electric current. Because of this effect, the liquid may break down into simpler substances, produce bubbles, change color, or deposit metal on the electrodes. This effect is used in electroplating, electrolysis, and purification of metals.

Conductors and Insulator

Conductors are materials that allow electric current to pass through them easily. They have free electrons that help in the flow of electricity. Examples: copper, aluminium, iron, saltwater, and the human body. Insulators are materials that do not allow electric current to pass through them easily. They have very few free electrons, so electricity cannot flow. Examples: rubber, plastic, wood, glass, and dry air. Conductors are used for making wires, while insulators are used for covering and protecting those wires to ensure safety.There are also some material which conduct electricity under specific conditions, these are called semi-conductors. They are not completely bad conductors. Example-Tungsten Filament in a Bulb

Good and Poor Conductors

Good conductors are materials that allow electric current to pass through them easily. They have many free electrons that help electricity flow. Examples: copper, aluminium, silver, gold, iron, saltwater, and graphite.Poor conductors (also called bad conductors) are materials that do not allow electric current to pass through them easily. They resist the flow of electricity because they have very few free electrons. Examples: rubber, plastic, wood, glass, paper, and pure distilled water. Good conductors are used for making electrical wires, while poor conductors are used for insulation and safety.

Experiment: Electrolysis of Copper Sulphate

This experiment helps to demonstrate the chemical effect of electric current by passing current through copper sulphate solution and observing deposition/dissolution of copper on electrodes.

Materials

• Copper sulfate solution (about 0.5 M) in a beaker
• Two copper strips (electrodes) cleaned with sandpaper
• 5–6 V DC source (battery or DC power supply)
• Connecting wires with crocodile clips
• Switch (optional)
• Beaker stand / clamp
• Safety goggles and gloves
• Filter paper and spatula (optional, for observing deposits)

Circuit/Setup

Place the two copper strips in the copper sulfate solution, a few centimetres apart, connected to the + and − terminals of the DC source by wires. Close the circuit so current flows through the solution.

Procedure

1. Clean the copper strips to remove oxide/grease so you can see metal change clearly.
2. Fix the strips vertically in the solution so they don’t touch.
3. Connect one strip to the positive terminal of the battery (anode) and the other to the negative terminal (cathode). If using a switch, keep it open.
4. Close the switch / connect the battery so electric current passes through the solution. Keep the current for 5–15 minutes.
5. Observe the electrodes and the solution periodically.

Observations

• The copper strip connected to the negative terminal (cathode) gets a brownish/metallic deposit (copper metal deposits).
• The copper strip connected to the positive terminal (anode) becomes thinner and may lose mass (it dissolves).
• The blue colour of the copper sulfate solution may become paler near the anode as Cu²? ions are consumed/diffuse.

Chemical explanation / Equations

• At the anode (positive): copper metal oxidises and goes into solution as ions.
  Cu (s) → Cu²? (aq) + 2 e?
• At the cathode (negative): Cu²? ions gain electrons and deposit as copper metal.
  Cu²? (aq) + 2 e? → Cu (s)

Net effect: copper from anode dissolves and is redeposited on the cathode — a clear chemical change caused by electric current.

Conclusion

Passing electric current through copper sulfate causes chemical reactions at the electrodes (oxidation and reduction). This demonstrates the chemical effect of electric current.

Precautions / Safety

• Wear safety goggles and gloves.
• Do not use high voltage — stick to low-voltage DC (1.5–6 V).
• Ensure electrodes don’t touch.
• Dispose of the solution responsibly or reuse it for demonstration.

Applications

 Real-life uses

• Electroplating (coating objects with a thin metal layer)
• Electrorefining and purification of metals
• Electrolytic production of chemicals

Electroplating

Electroplating is the process of coating one metal object with a thin layer of another metal using the chemical effect of electric current. In this process, the object to be plated is connected to the negative terminal (cathode) of a battery, and the metal that will form the coating is connected to the positive terminal (anode). Both are dipped in a solution containing salt of the coating metal. When electric current passes through the solution, metal from the anode dissolves into the solution and gets deposited on the object at the cathode. This gives the object a shiny, protective, and corrosion-resistant surface.

Experiment of electroplating

1. Take distilled water in a beaker and dissolve some copper sulphate in it. Add a few drops of dilute sulphuric acid to make the solution more conducting.
2. Take two clean copper plates. Clean them with sandpaper, wash with water, and dry them.
3. Connect the two copper plates to the terminals of a battery using connecting wires.
4. Immerse both plates in the copper sulphate solution without letting them touch each other.
5. Allow electric current to pass through the circuit for about 15 minutes.
6. Remove the plates (electrodes) and observe the changes.

Observation

• The plate connected to the positive terminal (anode) looks corroded.
• The plate connected to the negative terminal (cathode) gets coated with a thin layer of copper metal.

Analysis

• These changes occur due to the Chemical Effects of Electric Current.
• When electric current passes through the copper sulphate solution, it dissociates into copper ions (Cu²?) and sulphate ions (SO4²?).
• The free copper ions move towards the negative terminal and get deposited on the copper plate connected to the negative terminal.
• The copper plate connected to the positive terminal dissolves slowly, releasing copper ions into the solution. This replaces the copper ions deposited on the cathode.
• This continuous transfer of copper from the anode to the cathode is called Electroplating.

Applications of Electroplating

• Artificial jewellery made from inexpensive metals is coated with a thin layer of precious metals such as gold or silver to make it shiny, attractive, and affordable.
• In industries, electroplating is used to provide a protective layer on metal objects to prevent rusting, corrosion, and to give a smooth, glossy appearance (e.g., chromium plating on car parts, taps, and tools).

Do Liquids Conduct Electricity?

Liquids can conduct electricity when they contain dissolved salts, acids, or bases. Most conducting liquids are actually solutions of acids, bases, or salts, because these substances dissociate into ions when dissolved in water. These ions (positive and negative) help carry electric current through the solution, making it a good conductor. Distilled water, however, is a poor conductor of electricity because it has no dissolved salts or minerals, and therefore no ions. But when acids, bases, or salts are added to distilled water, they release ions into the solution, allowing the liquid to conduct electricity when a potential difference is applied.

Textbook Solutions

1. Fill in the blanks.
2. Most liquids that conduct electricity are solutions of ______________ and ______________.
3. The passage of an electric current through a solution causes ______________ effects.
4. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___________terminal of the battery.
5. The process of depositing a layer of any desired metal on another material by means of electricity is called _________.

Answer:

1. Most liquids that conduct electricity are solutions of acids, basesand 
2. The passage of an electric current through a solution causes chemical
3. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
4. The process of depositing a layer of any desired metal on another material by means of electricity is called 
5. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Answer: When the free ends of a tester are dipped into a solution and the circuit is complete, an electric current flows through the solution. Electric current always produces a magnetic field around the conductor. The magnetic needle of the compass is sensitive to magnetic fields. So, when current flows through the solution, the magnetic field produced by the current causes the magnetic needle to deflect. This deflection indicates that the solution conducts electricity.

3. Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.

Answer:

Saltwater, Lemon juice and Vegetable oil are the 3 liquids that can be taken in a beaker to show the passage of electricity, as they will show a deflection in the magnetic needle.

4. The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.

Answer: The bulb may not glow due to the following reasons:

1. The liquid act as a switch here but if it is a very poor conductor or it is completely non-conducting, the circuit is incomplete or open which can disconnect the flow of continuity of current.
2. Electric current may be very weak due to weaker battery, which is insufficient for the light to glow.
3. A tester is used to check the conduction of electricity through two liquids, labeled A and B. It is found that the bulb of the tester glows brightly for liquid A, while it glows very dimly for liquid B. You would conclude that
   1. Liquid A is a better conductor than liquid B.
   2. Liquid B is a better conductor than liquid A.
   3. Both liquids are equally conducting.
   4. Conducting properties of liquid cannot be compared in this manner.

Answer: (A) Liquid A is a better conductor than liquid B. The brightness of the bulb depends on how many electric current flows through the liquid. A brightly glowing bulb indicates high current due to good conductivity while a dimly glowing bulb haslow current as it is s poor conductor. Since the bulb glows brightly for Liquid A and dimly for Liquid B,Liquid A conducts electricity better than Liquid B.

6. Does pure water conduct electricity? If not, what can we do to make it conduct?

Answer: No, pure water does not conduct electricity because it does not contain any dissolved salts or minerals. These impurities are needed to provide ions, which help carry electric current. To make pure water conduct electricity, we can add a small amount of acid, base, or salt (for example, lemon juice, salt, or baking soda). These substances release ions in the water, allowing it to conduct electricity.

7. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

Answer: Water is a good conductor of electricity when it contains impurities (which it usually does).
During a fire, if the electrical supply is not turned off, the water sprayed from hoses can conduct electricity which can lead to electric shock to the firemen and people nearby . It can also lead to short circuits and make the situation more dangerous. Therefore, the main electrical supply is shut off to prevent electrocution and ensure the safety of firemen while they use water to extinguish the fire.

8. A child staying in a coastal region tests the drinking water and also seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Answer:  Seawater contains a large amount of dissolved salts, which break into ions. These ions allow electric current to pass through the water easily, making seawater a very good conductor of electricity. Drinking water, on the other hand, contains far fewer dissolved salts, so it conducts electricity less effectively. Because seawater conducts more current, the magnetic field produced is stronger, causing the compass needle to deflect more.

9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpours? Explain.

Answer:  No, it is not safe for an electrician to carry out electrical repairs outdoors during heavy rain. Rainwater contains impurities and becomes a good conductor of electricity. If the electrician works on electrical wires or equipment in the rain, there is a high risk of electric shock. Wet surroundings, wet hands, and wet tools increase the chance of short circuits, electrocution, and serious accidents. Therefore, electrical repairs should not be done during heavy downpours for safety.

10. Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reasons?

Answer: Rainwater is composed of a certain percentage of dissolved salts making it conductive. This results in the deflection of the compass.

11. Prepare a list of objects around you that are electroplated.

Answer:

1. Jewellery – gold or silver plated rings, bracelets, and necklaces.
2. Cutlery – spoons, forks, and knives with silver plating.
3. Watches – watch cases and straps with gold or chrome plating.
4. Coins – some coins have a layer of nickel or copper.
5. Car parts – bumpers, rims, and grills with chrome plating.
6. Bathroom fittings – taps, showerheads, and faucets with chrome plating.
7. Electrical connectors – copper or gold-plated connectors for better conductivity.
8. Pens – metal pens with gold or chrome plating.
9. Medals and trophies – gold, silver, or nickel plated.

12. The process that you saw in Activity 14.7 is used for the purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from the impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?

Answer: The thick rod of the impure copper plate is to be attached to the positive terminal of the battery because when the electric current is passed through the copper sulphate solution, it gets dissociated into copper and sulphate. The free copper, being positively charged, gets drawn to the negative terminal of the battery and gets deposited on it. On the other hand, the loss of copper from the solution is regained from the impure copper rod, which is attached to the positive terminal of the battery.