GCSE Chemistry (AQA)
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Properties of Small Molecules
- Small molecules have a simple covalent structure.
- Examples include hydrogen (H2), ammonia (NH3), and carbon dioxide (CO2).
- Ball and stick models represent these molecules, showing covalent bonds.
- Small molecules have a fixed number of atoms; e.g., CO2 is always CO2.
- Many substances, like water (H2O), are made up of small molecules.
- Water consists of two hydrogen atoms bonded to an oxygen atom.
- A glass of water contains approximately 6.7 septillion molecules.
- Strong covalent bonds exist between atoms in a molecule.
- Weak intermolecular forces exist between molecules.
- Melting or boiling involves overcoming weak intermolecular forces.
- Covalent bonds within molecules remain intact during phase changes.
- Substances with small molecules have low melting and boiling points.
- Water has a melting point of 0��C and a boiling point of 100��C.
- Small molecules are often liquids or gases at room temperature.
- Larger molecules have stronger intermolecular forces and higher melting/boiling points.
- Bromine (Br2) and iodine (I2) illustrate size-related boiling point differences.
- Small molecules do not conduct electricity due to lack of overall electric charge.
- Neutral molecules, like oxygen, do not allow charge flow, preventing electrical conduction.
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