6.6 The Electrical Properties of Condensed Phases

Conductor: is a material that completes an electric circuit so conducts electricity.

Insulator: is a material that does not completes an electric circuit so does not conduct electricity

Electric current: is the movement of electric charge.

Electrolyte: a substance that dissolves in water producing electrically conducting solutions, example: aqueous solution of sodium chloride.

Non-electrolyte: a substance that dissolves in water producing electrically nonconducting solutions, example aqueous solution of sugar and distilled water. Water itself is a bad conductor of electricity. When small quantities of a certain substance are dissolved in water,water becomes a good conductor of electricity.

Examples of electrolytes:

1- All Acids are electrolytes e.g acetic acid CH3COOH, sulphuric acid H₂SO4...

2- Most ionic compounds are electrolytes e.g NaCl, CaCl₂, MgBr₂

Remember

Ionic compounds are compounds made from reacting a metal with a non metal

Covalent compounds are compounds made from reacting a non metal with another non metal

Ions: are charged particles( charged atoms or groups of atoms)

Cations: positively charged ions (usually metal ions e.g. Na⁺, Ca²⁺..)

Anions: negatively charged ions ( non-metal ions, e.g. Cl⁻, CO₃²⁻)

Ionic compounds: are compounds in which oppositely charged ions are held together strongly by an electrostatic force of attraction. They are formed from the reaction between a metal and a non-metal. Examples of ioninc compounds are sodium chloride (table salt), NaCl,calcium chloride, CaCl₂, and silver nitrate, AgNO₃

Sodium chloride NaCl is made from the combination of sodium ions Na⁺ and chloride ions Cl⁻in a ratio of 1:1. When one mole of sodium chloride dissolves in water it provides the solution with two moles of ions( 1mole of sodium ions and 1 mole of chloride ions) as per the equation: NaCl(s) →Na⁺q)+Cl⁻aq)

Calcium chloride is made from the combination of calcium ions Ca²⁺ and chloride ions Cl⁻ in a ratio of 1:2. When one mole of calcium chloride dissolves in water it provides the solution with three moles of ions( 1mole of calcium ions and 2 moles of chloride ions) as per the equation: 

CaCl₂(s) → Ca²⁺(aq) + 2Cl⁻(aq).

Silver nitrate AgNO₃ is made from the combination of silver ions Ag⁺ and nitrate ions NO₃⁻  in a ratio of 1:1. When one mole of silver nitrate dissolves in water it provides the solution with two moles of ions( 1mole of silver ions and 1 mole of nitrate ions) as per the equation: 

AgNO₃ (s) → Ag⁺(aq) + NO₃⁻(aq)

Sodium chloride and all other ionic compounds are electrolytes because they provide the solution with freely moving ions which can carry electric charge.

An electric current flows when we have a complete circuit. Current flows outside the battery from the positive terminal to the negative terminal. If an ionic solution is connected to a battery, all positive ions move in the direction of the current, away from the positive electrode and towards the negative electrode. All negative ions move in a direction opposite to the current, away from the negative electrode and towards the positive electrode.

Memorize name and formulae of cations and anions listed

Naming ionic compounds: cation is always named first followed by the anion

Sodium Chloride 

Magnesium Bromide

Aluminium oxide

Writing the formulae of ionic compounds

Scientists say that a property is fundamental when it is generally observed but for which search

has failed to yield a useful model