What are the three groups into which all the elements can be divided? Name two elements belonging to each group.

Name two solid, two liquids and two gaseous elements at the room temperature.

Explain why, hydrogen and oxygen are considered elements whereas water is not considered an element.

State two physical properties on the basis of which metals can be distinguished from non-metals.

Compare the properties of metals and non-metals with respect to (i) malleability (ii) ductility, and (iii) electrical conductivity.