Explain the following statements:
- Most metal oxides are insoluble in water but some of these dissolve in water. What are these oxides and their solutions in water called?
- At ordinary temperature, the surface of metals such as magnesium, aluminium and zinc, etc. is covered with a thin layer. What is the composition of this layer? State its importance.
- Some alkali metals can be cut with a knife.
- These oxides are called basic oxides and their solutions in water are called alkalis.
- This layer formed is protective oxide layer which prevents the metal from further oxidation.
- Some alkali can be cut with a knife because they are very soft and have low densities.