A roadside worker uses solid sodium chloride to help melt ice on a footpath. Fig. 1 shows salt crystals spread over the icy surface. icesalt crystals© EAGLE...
Question 1 Report
A roadside worker uses solid sodium chloride to help melt ice on a footpath. Fig. 1 shows salt crystals spread over the icy surface.
(a) Name the state of sodium chloride before it dissolves. [1]
(b) Give the name of the mixture formed when sodium chloride dissolves in melted water. [1]
(c) Suggest why salt can make ice melt at a temperature below 0 degrees C. [2]
(d) Give one reason why workers should use only the amount of salt needed. [1]
(e) What happens to the arrangement of water particles when ice becomes liquid water? [1]
Answer Details
(a) Before dissolving, sodium chloride is a solid [1].
(b) The mixture made is a salt solution, or sodium chloride solution [1]. A solution is formed when a solute dissolves in a solvent.
(c) Dissolved salt lowers the freezing point of water [1]. Therefore, ice can change to liquid water at temperatures below \(0\degree\text{C}\) [1].
(d) Using only the necessary salt reduces waste, cost, or possible damage to plants and soil [1].
(e) On melting, water particles change from a regular, fixed arrangement to a random arrangement in which they can move past one another [1].
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