An example of metaphor in popular science writing:
"Lithium is a bewitching element and, when in the form of lithium chloride powder, absorbs moisture from the air and melts before your eyes."
de Moore, G., & Westmore, A. (2016). Finding Sanity. John Cade, lithium and the taming of bipolar disorder. Allen & Unwin.
LiCl is deliquescent. That means it is not just hygroscopic (i.e., able to absorb water from the atmosphere) but absorbs sufficient water to dissolve and form a solution.
Melting is quite different from dissolving as it produces a pure liquid not a mixture (solution). Lithium chloride melts at 605˚C: considerably above room temperature
Learners may not appreciate that melting and dissolving are quite distinct (as the difference is more obvious from a theoretical description than from what may be observed, e.g., an ice cube in a glass of water versus a sugar cube in a glass of water). For example, a learner may suggest that sugar melts when placed in water.
However, in everyday language things are said to 'melt away' with a much wider range of application than actual melting. I am assuming the authors here are using 'melt' in a metaphorical sense and do not hold the misconception that the solid anhydrous LiCl actually melts.
Read about metaphor in science
Read about examples of science metaphors
Many examples of science metaphors are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
