Fill in the following blanks with suitable words: (a) Magnesium liberates gas on reacting with hot boiling water. (b) The white powder formed when magnesium ribbon burns in oxygen is of . (c) Ordinary aluminium stripes are not attacked by water because of the presence of a layer of on the surface of aluminium. (d) A metal having low melting point is but a non-metal having very high melting point is . Calcium is a reactive metal than sodium.