The following power point discusses about the Chemical Effects of Electric Current. In this, we study about how electricity is conduced in liquids, electrolysis and the uses and applications of it

1. CLASS 8th Prepared by:
Bhavya Vashisht

2. CONDUCTORS
 Good conductors: Materials which allow electric current to pass
through them easily
 Example: Metals: Copper and Aluminum
 Poor/ Non conductors: Materials which don’t allow electric
current to pass through them
 Examples: Rubber, plastic, wood etc.

3. Liquids conducting electricity
 Liquids that conduct electricity are solutions of acids,
bases & salts in water.
 Examples:
 Acid: Solution of Sulphuric acid (H2SO4) water
 Base: Solution of Sodium hydroxide (NaOH) in water
 Salt: Solution of Sodium Chloride (NaCl) in water

4. Differences in conduction of electricity by solids and liquids
1. In solids, electricity is carried by electrons, but in liquids, electricity is
carried by ions
 In solid like copper metal, electricity is carried by electrons but in
liquids like copper sulphate solution (CuSO4), electricity is carried by
Copper (Cu2+) and sulphate (SO4
2-) ions. Positive charged ions are
called Cations and negatively charged ions are called Anions.
2. When electricity is passed through solid, no chemical change occurs,
but in liquids, when electricity is passed, chemical change takes place.
 When electricity is passed through copper wire, no chemical change
occurs, but when passed through acidified water, chemical change
takes place in which water is decomposed into hydrogen and oxygen
gases

5.  Conducting liquids: liquids which conduct electricity
 The chemical changes which take place in conducting liquids on
passing electric current through them are called chemical effects of
current.
 Electrolyte: Liquid (or solution of substance) which conduct
electricity
 Electrolyte/ Conducting liquid contains ions (Cations & Anions)
 Flow of these ions conduct electricity
 Solutions of acids, bases, salts in water are electrolytes
 Types of electrolytes
 Strong electrolyte: Liquid (or solution) which conducts electricity
very well. This is because it has many ions. Example: Sulphuric acid
solution, Sodium hydroxide solution, Sodium chloride solution
 Weak electrolyte: Liquid (or solution) which conducts electricity to
lesser extent. This is because it has less ions. Example: Vinegar
(Acetic Acid solution), Lemon juice (Citric Acid solution), tap water
and rain water

6. Electrolytic cell
 Electrode: Solid electrical conductor though which electric current
enters or leaves like a dry cell or an electrolytic cell.
 They are mainly made up of Carbon or metal
 Types of electrodes:
 Cathode: Electrode connected to negative terminal of battery. It has
negative charge
 Anode: Electrode attached to positive terminal of battery. It has
positive charge.
 Electrolytic cell: Arrangement of 2 electrodes kept in conducting
liquid (electrolyte) in a vessel
 Electrolytes are not as good conductors of electricity as metals are. So,
a single electric cell is not enough to study conduction of electricity
through liquids. Hence, we require a battery made up of number of
cells

8. SOLUTION
Testing Conductivity of liquids

9. Testing Conductivity of liquids
 Good conductors: The glowing bulb in this case tells us that
hydrochloric acid solution is a very good conductor of electricity
 Weak conductors: The very dim glowing of bulb indicates that
though vinegar and lemon juice conduct electricity, but they are
weak conductors of electricity
 Very weak conductors: The bulb don’t glow at all even when
we attach large battery. This is because water is very weak
conductor of electricity.

10. Detection of weak current flowing through
liquid
 Current flowing in circuit usually detected by small electric bulb.
When electricity flows through bulb, then due to the heating effect of
current, the filament of bulb gets heated to high temperature, becomes
white hot and glows to produce light
 If the current flowing through circuit is too weak, then heating effect
produced by current in the filament is too little, due to which filament
doesn’t get heated sufficiently & hence bulb doesn’t glow at all.
 Weak electric current flowing through liquid can be detected by
1. Using LED (Light Emitting Diode)
2. Using a compass

11. LED

12.  We can use LED in place of small bulb foe detecting weak electric
current. LED glows even when very weak current passes through it.
 2 wires (leads) are attached to LED. 1 is long which is connected to
positive terminal of battery and small lead is connected to negative
terminal of battery.
 We can also detect weak electric current flowing through liquid by
using a compass.
 If a compass surrounded by wound up electrical wire of a circuit
including a liquid in it shows deflection, it means that liquid conducts
electricity

13. Case of Distilled water, Tap water, Sea water & Rain water
 Distilled water don’t conduct electricity.
 We can make distilled water (pure water) conduct electricity by:
Adding little acid, Base or Salt
 Tap water conducts electricity because it contains small amount of
various salts in it
 Drinking water contains small amounts of salts in it, hence it conducts
electricity
 Sea water has high amount of salt in it, hence it conducts electricity
 Due to presence of small amount of acid in rain, rain water conducts
electricity

14. CHEMICAL EFFECTS OF ELECTRIC CURRENT
 Electric current can bring about chemical changes
 When electric current is passed through acidified water by using carbon electrodes, a
chemical reaction takes place to form hydrogen gas and oxygen gas
 Water------------------------------------ Hydrogen + Oxygen
 A chemical compound (water) has been chemically decomposed into Hydrogen and
Oxygen because of passing of electric current.
 Electrolysis: Chemical decomposition produced by passing current through
conducting liquid (electrolyte)
 Chemical effects produced by electric current depend on nature of conducting
solution (through which it’s passed) and nature of electrodes being used for passing
electric current.
 Examples: Bubbles of gases (Acidified Water), deposition of metals (Electroplating)
& change in color (cut potato)
Electric Current

16. APPLICATIONS
1. Electroplating metals
2. Purification of metals
3. Production of certain metals from ores
4. Production of chemical compound: (Sodium Hydroxide/
Caustic Soda is produced by Electrolysis of aqueous
solution of Sodium Chloride)
5. Decomposing chemical compound: (Water forming
Hydrogen and Oxygen)

19. PURIFICATION OF METALS

20. THANK YOU