When ethanol is heated with excess concentrated sulphuric acid, the ethanol is?

Concentrated sulphuric acid removes water from ethanol. Heated in excess acid at about 170°C:

C₂H₅OH → C₂H₄ + H₂O

Ethanol loses water, so it is dehydrated to ethene. It is not oxidised, because no oxygen is added. Ethyne would need loss of more hydrogen. Polyethene forms from ethene with a different catalyst, not here.