CHEMISTRY

• Covalent compounds involve non-metal and non-metal sharing of electrons
• Covalent compounds have low melting point and boiling point
• Covalent compounds cannot conduct electricity
• This is because they have weak forces of attraction between molecules
• This is because they don't have free-moving electrons
• They also don't have ions
• Group 1 elements are the Alkali metals
• Alkali metals react with water to produce soluble hydroxides (alkalis) and hydrogen gas
• Alkali metal + Water → Alkali hydroxide + H2 gas
• Acids have a pH lower than 7 (1-6) and donate protons
• Alkalis have a pH higher than 7 - 14 and accept protons
• Salts have a pH of 7 (neutral)
• Bases accept protons
• All acids contain Hydrogen ions (H+)
• All alkalis contain hydroxide ions (OH-)
• Water is neutral because it contains both a negative (OH-) and a positive (H+) ion, resulting in neutrality
• pH Scale:

  • Acids have a pH lower than 7
  • Alkalis have a pH higher than 7
  • Salts have a pH of 7 (neutral)
• Indicators:

  • Acid in litmus turns red
  • Acid in Phenolphthalein is colorless
  • Acid in methyl orange turns red
  • Acid in universal indicator turns red, yellow, or orange
• Indicators:

  • Alkali in litmus turns blue
  • Alkali in Phenolphthalein turns pink
  • Alkali in Methyl orange turns yellow
  • Alkali in Universal indicator turns blue or purple
• Common acids:

  • Nitric acid: HNO3
  • Sulphuric acid: H2SO4
  • Hydrochloric acid: HCl
• Types of acids:

  • Weak acids have a pH of 4-6
  • Strong acids have a pH of 1-3
• Partially ionized water when added to acids
• Common alkalines:

  • Sodium hydroxide: NaOH
  • Calcium hydroxide: Ca(OH)2
  • Potassium hydroxide: KOH
• Types of alkalines:

  • Weak alkalines have a pH of 8-11
  • Strong alkalines have a pH of 12-14
• Partially ionized in weak alkalines

  • Completely ionized in strong alkalines
  • Ionized substances have charges, e.g., KOH + Water produces K+ and OH-
• When acids react with metals, they form salts and hydrogen gas
• Example: Hydrochloric acid + Sodium → Sodium chloride + Hydrogen
• Reactions of salts involve acids reacting with metal oxides
• Example: Nitric acid + Sodium > Sodium nitrate + water
• Acids:
• Hydrochloric acid:

  • Chemical formula: HCl
• Sulphuric acid:

  • Chemical formula: H2SO4
• Nitric acid:

  • Chemical formula: HNO3
• When acids react with metal carbonates, the products formed are salt, carbon dioxide, and water
• The general reaction for this type of reaction is: Acid + Metal → Salt + Carbon dioxide + Water
• Neutralisation reaction: Acid + Alkaline → Salt + water
• Acid and alkaline react to form a salt and water
• The combination of acid and alkaline results in a neutral solution
• Example reactions:

  • Sulfuric acid + Ammonium hydroxide → Ammonium sulphate + water
  • Nitric acid + Magnesium hydroxide → Magnesium nitrate + water
• All alkaline substances contain hydroxide