Classification of Matter
Elements
- Substances that consist of only one type of atom
- Examples: hydrogen (H2), oxygen (O2), carbon (C)
Compounds
- Substances formed by the chemical combination of two or more elements
- Examples: water (H2O), carbon dioxide (CO2), ammonia (NH3)
Mixtures
- Physical combinations of two or more substances
- Examples: air, soil, seawater
Chemical Changes
Chemical Reaction
- A process in which one or more substances are converted into new substances
- Examples: burning of wood, rusting of iron
Types of Chemical Reactions
- Combination reactions: 2H2 + O2 → 2H2O
- Decomposition reactions: 2H2O → 2H2 + O2
- Displacement reactions: Zn + CuSO4 → ZnSO4 + Cu
- Double displacement reactions: Na2SO4 + BaCl2 → BaSO4 + 2NaCl
Chemical Properties
Reactivity
- The ability of a substance to undergo a chemical change
- Examples: metals react with acids, non-metals react with oxygen
Melting and Boiling Points
- The temperatures at which a substance changes state
- Examples: ice melts at 0°C, water boils at 100°C
Acids, Bases, and Salts
Acids
- Substances that donate H+ ions or release hydrogen gas
- Examples: hydrochloric acid (HCl), sulphuric acid (H2SO4)
Bases
- Substances that accept H+ ions or release hydroxide ions (OH-)
- Examples: sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2)
Salts
- Substances formed by the reaction of acids and bases
- Examples: sodium chloride (NaCl), sodium sulphate (Na2SO4)
These notes cover the key concepts related to chemical substances, including classification, chemical changes, chemical properties, and acids, bases, and salts.
