How does the amount of matter change when water changes state?

The amount of matter will be the same - matter cannot be destroyed or created.

Explanation:

The state of matter could change, however, e.g. solid to liquid.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).

fe 55.85 g/mol and h2o 18.02 g/mol.