(1) If the same alcohol lamp is heated for a long time, the sand will absorb more heat. Therefore, the length of heating time indicates how much heat is absorbed.

(2) Water and sand with the same mass are heated at the same temperature. According to Q=cm△t, the greater the specific heat capacity of water, the more heat it absorbs. So water absorbs more heat than sand.

(3) Water and sand with the same mass are heated for the same time, indicating that the heat absorbed is equal. According to Q=cm△t, the specific heat capacity of sand is small, and the temperature is high. Then the increased internal energy of the two is equal.

So the answer is: (1) How much heat is absorbed; (2) greater than; (3) sand; Equality.