Chemical Effects of Electric Current: When an electric current flows via a conducting solution, chemical reactions take place in the solution. This process can be described as the chemical effect of electric current. An excellent example of the chemical effect is when an electric current is passed through the solution of a metal salt; such as a solution of copper sulfate; copper metal gets deposited at the negative electrode as the metal is positively charged. Thus we can easily separate metal from its salt using this method.

Chemical Effects of Electric Current: Overview

Let us start with an experiment. Take a beaker, and fill it with tap water. Take a wire to connect a battery and bulb and form a circuit. Dip the two ends of the wires into the beaker containing water or any liquid without touching each other, but also keep in mind that a large distance does not separate them.

As shown in the figure below:

What will you observe? Does the bulb glow? Yes, it does. This means that the liquid in the beaker is conducting electricity.

Now, in the same set-up, replace tap water with salt water. Did you find any change in your observation?
Yes, you will see that the bulb starts to shine brighter than in the previous set-up. Thus, we can conclude that some liquids are better conductors of electricity.
Now replace the saltwater with distilled water and repeat the entire process, as shown in the figure below?

Now, would you find any change in your observation? Yes, the bulb stops glowing! Thus, we can conclude that some liquids are insulators.
To learn how some liquids can conduct and what happens when they do, read further and understand the chemical effects of electric current!

What are Good Conductors and Good Insulators?

Good conductors are the materials that allow the electric current to pass through them easily. Most metals like copper, aluminium and iron are good conductors of electric current.

Good insulators are materials that do not allow the electric current to pass through them quickly. Materials like rubber, plastic and wood are insulators.

Here, it is important to understand that most materials are under certain conditions conduct. That is why we prefer to categorise materials as good conductors and good insulators instead of just conductors and insulators. To understand this, take the example of air. We know that air is a poor conductor of electricity (to check this, repeat the experiment given at the top, but this time leave the two ends of the wire open in your surroundings, and you will find that the bulb does not glow). But we have all seen electric currents pass through the air during lightning ( That is why it is advised to stay indoors during lightning). This shows that air can conduct under certain conditions, and the same thing is true for most objects around us.

Can Liquids Conduct Electricity?

We can state that liquids can conduct electricity from the experiment we performed above, although it is not valid for all liquids. Most of the liquids that conduct electricity are a solution of either acids or bases or salts. For example, lemon juice is a good conductor of electricity, while vegetable oil is a good insulator. The water that we get from natural sources like handpumps, tanks, and ponds is not pure. It contains various minerals and salts dissolved, making natural water a good conductor of electricity. But pure, distilled water is devoid of all minerals and salts, which is why it is an insulator. As we increase the number of impurities in the water, the conductivity of the water increases up to a certain point; that is why salty water is a better conductor than tap water.

What Happens when an Electric Current is Passed through a Conducting Solution?

When an electric current passes through a conducting solution, a chemical reaction takes place within the solution. For example, when an electric current is passed through water, it ionizes water into ions. Thus, we get \(H^+ (aq)\) and \(OH^- (aq)\) ions. Here the \(H^+ (aq)\) ions move towards the cathode( the negative electrode) to gain electrons and form \(H_2\), while the \(OH^- (aq)\) ions move towards anode( the positive electrode) to lose electrons and form \(O_2\). These, among others, are the chemical effects of electric current.

What are the Chemical Effects of Electric Current?

William Nicholson, a British chemist, demonstrated in \(1800\) that when you immerse two electrodes in water and pass an electric current through that water, you will see oxygen and hydrogen bubbles. At the electrode connected to the positive terminal of the battery, you will find bubbles of oxygen. In contrast, at the electrode connected to the battery’s negative terminal, you will find bubbles of hydrogen gas.
The chemical reactions that occur within a conducting solution as electric current is passed through it are known as the chemical effects of electric current. These reactions are quite common and essential to us. Some of the chemical effects of electric current are:

1. Bubbles of gas formed at electrodes.
2. Deposits of metal are seen on electrodes.
3. Change of colour of the solution.
4. Electroplating

Electroplating

The process by which a layer of the desired metal is deposited over other material by an electric current is known as Electroplating. It is the most useful and common application of the chemical effects of electric current. It is frequently used for industrial purposes for coating metal objects with the desired layer of another metal. This is done to compensate for a required property in which the given metal object lacks.

Applications of Electroplating

1. Chromium coating is done on various materials like car parts, gas burners, bath taps, bicycle handles and wheel rims. Chromium has a shiny appearance and does not corrode, and it resists scratches. But chromium is expensive, and it is not economically viable to make objects out of chromium. Thus, the objects made from cheaper materials are coated over with a thin layer of chromium metal.
2. Jewellers often coat a thin layer of silver or gold over ornaments made from cheaper metals to give them an expensive and brighter appearance. Artificial jewellery made this way is less expensive than the original jewellery made from pure gold or silver.
3. Tin cans used at our homes for storing food are made by electroplating a thin layer of tin metal over iron. Iron is a reactive element; it will react with food and spoil it. To prevent this, a thin layer of tin ( which is much less reactive than iron) is coated over iron so that food does not come in contact with iron and stays safe to eat for a longer period.
4. Bridges and automobiles are made from iron because it provides them strength. But iron is prone to corrosion due to rusting. Iron is coated over with a layer of zinc metal to prevent it from rusting and corrosion.
5. Nickel and chromium-coated articles are used in automobiles and household appliances.

How is Electroplating Done?

To understand how a metal layer is coated over another metal object, let us take the example of electroplating a Silver Spoon with Gold.

1. The article to be electroplated (silver spoon) is taken as a cathode.
2. Take a thick plate of the metal to be deposited (gold plate) as an anode.
3. We wish to coat the silver spoon with gold, so take the acidified solution of the metal to be coated, i.e. gold chloride with hydrochloric acid, as an electrolyte.
4. Clean the silver spoon with a dilute acid solution. This ensures that the oxide layer is removed from the silver spoon’s surface.
5. Wash it in running water until it is from the acid.
6. Suspend the clean silver spoon in the acidified gold chloride solution (electrolyte) kept in a beaker.
7. Also, suspend a thick plate of gold (the anode) in the gold chloride solution.
8. Complete The circuit using a battery and key.
9. Allow current to pass through it for about \(15\) minutes.
10. Now, remove the electrodes from the solution.
    
11. You will obtain a gold spoon. Not exactly though, you will get a silver spoon coated with a thin layer of gold metal, making it look like a gold spoon.

Solved Examples on Chemical Effects of Electric Current

Let us look at some of the solved examples from Chemical Effects of Electric Current for Class 8 chapter :

Q.1. Would a compass needle deflect if it’s connected in a circuit containing a battery, wires and dipped in a container of water, as shown below? What would happen if we replace tap water with seawater?

Ans: As the current starts flowing through the circuit, we will observe a deflection in the magnetic field, indicating a magnetic field around the circuit. This is the magnetic effect of current. When tap water is replaced with seawater, we will observe a stronger deflection. This is because seawater contains more impurities than tap water and hence is a better conductor.

Q.2. What are electrodes and electrolytes?
Ans: Electrode: It is a conductor immersed in a solution with one end connected to a battery. It can either be an anode (positive) or cathode(negative) electrode.
Electrolyte: The solution in which electrodes are dipped. This electrolyte dissociates when an electric current is passed through it.

Q.3. Why do firefighters shut off the main electrical connection for the area before they use the fire hose?
Ans: We know that water is a good conductor of electricity, and the water used in fire hoses is not pure distilled water. Rather it is normal tap water, and such water, if it came in contact with electricity, can cause shocks. Thus, to save themselves and other people from electrocution, the firemen shut off the electric supply before spraying water

Q.4. Is rainwater an insulator?
Ans: We know that rainwater is pure water and is a poor conductor of electricity or an insulator. But as the rainwater reaches lower layers of the atmosphere, it gets mixed with pollutants like sulphur dioxide and nitrogen oxides. It leads to the formation of an acidic solution, which is a good conductor of electricity.

Summary About Chemical Effect of Electric Current

When an electric current is passed through a conducting solution, some chemical reaction occurs in the solution. Some of the chemical effects of electric current are Bubbles of gas formed at electrodes, Deposits of metal are seen on electrodes, Change of the colour of the solution and Electroplating. The process by which a layer of the desired metal is deposited over other material by an electric current is known as Electroplating

Also Check,

NCERT Solutions for Class 8 Science Chapter 14

Frequently Asked Questions (FAQs) on Chemical Effects of Current

The most commonly raised queries on Chemical Effects of Current are addressed here:

Q.1. What are the chemical effects of current? Ans: When an electric current flows through a conducting solution, within the solution, some chemical reactions take place. This is called the chemical effect of electric current.

Q.2. What is electrolysis? Ans: The decomposition of a chemical compound into its constituent ions by passing an electric current through its solution is electrolysis.

Q.3. What is Electroplating? Ans: The depositing of a layer of desired metal over another metal using electricity is known as Electroplating.

Q.4. What are conductors and insulators? Ans: Conductors are the materials that allow the electric current to pass through them—for example, copper, aluminium etc. Insulators are materials that do not allow the electric current to pass through them—for example, wood, rubber etc.

Q.5. What are the three chemical effects of current? Ans: Some of the chemical effects of electric current are as follows: 1. Gas Bubbles may be formed at electrodes 2. Metals may get deposited on electrodes 3. Change of colour of the solution.