AP.P.TON

CHEMICAL EFFECTSOF

ELECTRIC CURRENT

KNOW ABOUT CHARGES

To understand electricity and related terms, it is important to understand what charges are. The charges that carry electricity are present in basic unit of matter, that is in atoms. Atoms are the smallest particles of matter which combine together to form matter. Atoms are further composed of particles called electrons, protons, and neutrons. The protons are positively charged, electrons are negatively charged and neutrons are neutral. The total charge of an atom is neutral. The protons and neutrons remain in the nucleus, whereas the electrons move around the nucleus.All metallic elements have ‘free electrons’ in the outermost orbit. An electric current is set up when these free electrons move from one atom to another.

WHAT IS ELECTRIC CURRENT?Electric current is the flow of electrons.

MORE ABOUT ELECTRIC CURRENT :-The passage o electric current through substances is called conduction.Some materials allow electric current to pass through them whereas others do not. Also, conducting materials may behave differently when electric current is passed through them- some are decomposed and some are not.

CONDUCTORS AND INSULATORSAll substances do not allow electric current to pass through them. Based on this ability, substances are divided into two categories- conductors and insulators.Substances that allow heat or electricity to flow through them readily are called conductors. For example, metals and some non-metals such as graphite are good conductors of electricity.Substances that do not allow the free flow of charges through them are called insulators. For example, dry wood, plastic, rubber, wool and cotton are insulators.

DIRECTION OF ELECTRIC CURRENT

Charges flow from the positive terminal of the source to the negative terminal. That is why the flow of current in a circuit is marked from the positive terminal to the negative terminal using arrowheads. This current is also known as conventional current.

CHEMICAL CHANGES DUE TO ELECTRIC CURRENT

When electric current is passed through solutions, you might notice bubbles of gases. This is due to the occurrence of a chemical change. Change in the colour of solution, precipitation and change in temperature of solution can also be observed because of chemical reactions.

ELECTRICAL CONDUCTIVITY

Electrical conductivity is the ability of a substance to allow the flow of electric current. A substance may have a good conductivity irrespective of whether it is a solid or a liquid. A liquid with a good conductivity is called an electrolyte, and the one which is incapable of conducting electricity is called a non-electrolyte.

Electrolyte Non-electrolyte

Tap water Distilled water

Sulphuric acid Sugar solution

Nitric acid Spirit

Hydrochloric acid Acetone

Common salt solution Benzene

ELECTRICAL CONDCTIVITY OF WATER

Water that is not in the pure form becomes a good conductor

of electricity because of the presence of impurities. It is

always advised that while handling electrical appliances we

should ensure that our hands and feet are not wet, so that

electric current does not pass through our body and we do not

get an electric shock.

ELECTRICAL CONDUCTIVITY OF

OTHER LIQUIDS

Many liquids are good conductors of electricity. Several acids and bases when dissolved in water become good conductors of electricity. Lemon juice, vinegar, aqueous sodium chloride and aqueous potassium chloride are a few examples.

EFFECTS OF IMPURITIES ON ELECTRICAL CONDUCTIVITY OF

WATER

Although distilled water does not conduct electricity, ordinary tap water is a good conductor. This happens because the dissolved salts in the tap water increases the conductivity of water. For an electric current to flow, charged particles should move freely. These particles are also known as charged carriers since they carry the charges. In the metals, the charged carriers are the electrons. In liquids, these charged particles are ions(negatively or positively charged atoms).

ELECTROLYSISWe know that it is possible to pass electric current through water. When electric current is passed through water, it is possible to break it up into its individual components- oxygen and hydrogen. By passing electric current through aqueous common salt (sodium chloride), it is possible to split it into sodium and chlorine. The process by which a substance

is split into its components when electric current is passed through

it is called electrolysis. In other words, it is the chemical effect of electric current whereby electric

current causes a chemical change in the substance through which it

passes. An electrolyte, in liquid state or dissolved in water,

conducts the current and undergoes a change during

electrolysis.

The two plates or rods through which the current enters and leaves the electrolyte are called electrodes. The electrode at which the current enters the electrolyte is called the anode and the electrode at which it leaves is called the cathode. The anode is positively charged while the cathode is negatively charged. The arrangement consisting of a vessel, the electrolyte, the electrodes and a source of current is called an electrolytic cell.

ELECTROLYSIS OF COPPER CHLORIDE

When copper chloride solution is taken in a beaker and two carbon electrodes are placed in it to form a circuit, current flows through the solution once the connection s complete. As current passes through

the circuit, the ammeter shows deflection. Ammeter is a device used to measure current. After a while,

bubbles of a gas are observed at the anode. This gas smells of bleaching powder and is easily identifiable

as chlorine. The surface of the cathode becomes reddish due to deposition of copper. After a while as copper chloride splits into copper and chlorine, the bright blue colour of the copper chloride solution

starts fading.

ELECTROPLATING

Electroplating is a common application of electrolysis. The process of depositing a thin layer of a metal on any conducting substance by the process of electrolysis is known as electroplating. For example, chromium coating is done on car parts, bath taps, wheel rims, etc. In electroplating, the object to be electroplated is made the cathode (negative electrode)by connecting it to the negative terminal of the battery. The metal which has to be deposited is made the anode (positive electrode)by connecting it to the positive terminal of a battery. The electrolyte is usually a salt solution of the metal to be coated. On passing electric current, the object gets coated with the desired metal.

ACTIVITYAim: To demonstrate electroplating

Material required: iron key, copper plate, silver bar, solution of copper sulphate, beaker, three 9-V cells, wire

Procedure: Connect the key, copper plate and the battery with the wire to form a circuit. The key should be connected to the negative terminal of the battery and the copper plate to the positive terminal. Dip them in the solution of copper sulphate in a beaker and observe.

Observation: Once he circuit is connected, the process gets started and after some time, it is seen that the key gets a coating of copper.

Conclusion: The positive charges, that is copper ions, move towards the cathode, and the key is electroplated.

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