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Bonding, Structure & Energy · Part 2 of 3
15 exam-style questions with model answers, plus 20 quick multi-choice questions — every question on this part of the standard, grouped by the 5 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Name the four structure types and state the particles present in each.
Carbon dioxide is a gas at room temperature but silicon dioxide melts at 1710 °C. Both contain only non-metals and covalent bonds. Explain the difference.
A white solid does not conduct electricity when solid, dissolves in water to give a solution that conducts well, and melts at 770 °C. A second solid is grey, conducts electricity when solid, and melts at 660 °C. Deduce the structure of each, justify your deductions using all the evidence, and explain why a third substance melting at 3550 °C that does not conduct at all must be different from both.
State whether molecular substances have high or low melting points, and say what is overcome when they melt.
Explain why magnesium oxide has a much higher melting point than sodium chloride.
Explain why the boiling points of the group 17 elements increase from chlorine (−34 °C) to bromine (59 °C) to iodine (184 °C), and then explain why water, a much smaller molecule than iodine, still boils at 100 °C.
State the condition a substance must meet to conduct electricity.
Explain why solid potassium bromide does not conduct electricity but molten potassium bromide does.
Compare the electrical conductivity of copper, sodium chloride, diamond and graphite, explaining each in terms of structure and bonding. Account for why graphite behaves differently from diamond even though both are made only of carbon.
Define malleable and ductile, and state which structure type shows both properties.
Explain why diamond is extremely hard.
Sodium chloride and copper both have giant structures held together by strong forces, and both have high melting points. Explain why copper is malleable while sodium chloride is brittle, and evaluate the claim that 'sodium chloride shatters because its bonding is weaker than copper's'.
State the general rule for predicting solubility, and use it to say whether sodium chloride dissolves in hexane.
Explain, in terms of the particles involved, why sodium chloride dissolves in water.
A student is given three white solids: sodium chloride, sugar (a polar molecular substance) and wax (a non-polar molecular substance). Describe how solubility and conductivity tests could distinguish all three, and justify each prediction from the bonding and structure involved.