Hydrogen bonding and properties of waterEdexcel International A Level Chemistry: Mind map

Exam questions on Hydrogen bonding and properties of water

1. Water is an unusual substance. Ice floats on the surface of liquid water, whereas the solid form of most substances sinks in its own liquid. Each water molecule in ice is held in position by hydrogen bonds.
   Explain why ice floats on liquid water.2 marks
2. The boiling temperatures of the hydrides of the Group 16 elements are: hydrogen sulfide, H₂S, 213 K; hydrogen selenide, H₂Se, 232 K; hydrogen telluride, H₂Te, 271 K; water, H₂O, 373 K.
   Explain why the actual boiling temperature of water is much higher than the value predicted from the trend in the other hydrides.2 marks
3. Methane, CH₄, and water have similar relative molecular masses (16 and 18). Methane melts at 91 K and boils at 112 K. Water melts at 273 K and boils at 373 K. At 273 K the density of ice is 0.92 g cm⁻³ and the density of liquid water is 1.00 g cm⁻³.
   Explain why water has much higher melting and boiling temperatures than methane.3 marks