Question 1

What is NCEA AS 91164 about?

Accepted Answer

You need to show that you understand how atoms bond together, why the structure of a substance matters for how it behaves, and the energy released or absorbed when substances change. This standard covers different types of bonding (ionic, covalent, and metallic), what properties those substances have (like hardness or how well they conduct electricity), and how to explain and calculate energy changes in chemical reactions.

Question 2

What do students need to do for AS 91164?

Accepted Answer

1. Identify and describe the types of bonding (ionic, covalent, metallic) and intermolecular forces in substances, using correct chemistry symbols and Lewis structures 2. Link the bonding and structure of a substance to its physical properties—such as explaining why metals are malleable or why some substances dissolve in water 3. Determine molecular shape using VSEPR theory and decide whether molecules are polar or non-polar by considering electronegativity and symmetry 4. Recognise whether reactions are exothermic or endothermic and calculate energy changes using bond enthalpy values and reaction stoichiometry 5. Use correct units, significant figures, and chemical conventions (+ and − signs) in all calculations and explanations

Question 3

What's the difference between Achieved, Merit, and Excellence for AS 91164?

Accepted Answer

Achieved: You identify key concepts like types of bonding and shapes of molecules, do calculations correctly, and name what type of solid or particle is involved, but don't always explain the connections between ideas. Merit: You link bonding and structure to properties (for example, connecting metallic bonding to malleability), explain molecular shape using VSEPR theory and electronegativity, and round thermodynamic calculations properly with correct units and signs. Excellence: You compare and contrast different substances using specific evidence, justify your answers by referencing bonding and structure (for example, explaining why one ionic solid melts at a higher temperature than another), use annotated diagrams, and apply consistent scientific language throughout.

Question 4

What mistakes do students typically make in AS 91164?

Accepted Answer

1. Using vague terms like 'particles' instead of naming the actual type—say 'ions' or 'molecules' or 'atoms' instead of just 'particles' 2. Not recognising diamond as a 3D covalent network solid or failing to describe its structure, and attributing conductivity only to electrons when ions can also be mobile charge carriers 3. Forgetting to include signs (+ or −), units, and correct significant figures in energy calculations, or not linking the strength of forces between particles to the energy needed for melting or boiling

Bonding and structure

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AS91164 — Bonding, Structure and Energy

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