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Bhavya Vashisht, profile picture
Uploaded byBhavya Vashisht
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Chemical effects of electric current

The document explains the concepts of conductors, electrolytes, and the differences in how solids and liquids conduct electricity, emphasizing that electricity in solids is carried by electrons while in liquids it's carried by ions. It describes the classification of electrolytes into strong and weak, and outlines the use of LEDs and compasses for detecting weak currents. The document also covers the chemical effects of electric current, including electrolysis and applications such as electroplating and purification of metals.

Education◦
CLASS 8th Prepared by: Bhavya Vashisht
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.
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
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
 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
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
SOLUTION Testing Conductivity of liquids
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.
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
LED
 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
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
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
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)
PURIFICATION OF METALS
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