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VICChemistryQuick questions
Unit 1: How can the diversity of materials be explained?
Quick questions on Intermolecular forces and covalent substances: VCE Chemistry Unit 1
12short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is intermolecular forces (IMFs)?Show answer
Intermolecular forces are attractions between molecules, not within them. Breaking an IMF (boiling or melting a molecular substance) takes far less energy than breaking the covalent bonds inside a molecule.
What is three classes of covalent material?Show answer
Covalent molecular substances. Discrete molecules held together by IMFs in the solid and liquid states. Examples: water (H2O), sucrose (C12H22O11), iodine (I2), CO2 (dry ice). Properties:
What is allotropes of carbon?Show answer
Allotropes are different structural forms of the same element. Carbon has several worth knowing:
What are 1. Dispersion forces?Show answer
Present between all molecules (and atoms). They arise from instantaneous, fluctuating dipoles in the electron cloud of one molecule inducing a dipole in a neighbour. Strength increases with the number of electrons (and surface area).
What are 2. Dipole-dipole attractions?Show answer
Present only between polar molecules. The partial positive end of one molecule attracts the partial negative end of another. Stronger than dispersion (for molecules of similar size), but weaker than hydrogen bonds.
What is 3. Hydrogen bonding?Show answer
A special, particularly strong dipole-dipole interaction. Requires all three of:
What are covalent molecular substances?Show answer
Discrete molecules held together by IMFs in the solid and liquid states. Examples: water (H2O), sucrose (C12H22O11), iodine (I2), CO2 (dry ice). Properties:
What are covalent network substances?Show answer
Every atom in the solid is bonded covalently to its neighbours in a 3D giant lattice. There are no discrete molecules. Examples: diamond, silicon dioxide (quartz), silicon carbide.
What are covalent layered substances?Show answer
Atoms within a layer are covalently bonded, but layers themselves are held together by weak dispersion forces. The standout example is graphite.
What is q1?Show answer
Explain why methane boils at but water boils at , despite similar molar masses. [3 marks]
What is q2?Show answer
Rank the boiling points of , , , and explain the trend. [3 marks]
What is q3?Show answer
Compare graphite and diamond. (a) Describe the bonding in each. (b) State and explain one physical property that differs.