Making of a solar water heater :
Materials used :
1) 2 to 3 litre of one empty soda bottle.
2) Black paint
3) Aluminium foil
4) A cardboard
Take the soda bottle clean it properly and let to be dry. Now paint the bottle completely with black paint, so that it will absorb the heat radiation. Fill the empty bottle with water. Take the aluminium foil and paste it on the cardboard with the help of glue. Now place the cardboard in a sunny spot and the bottle in front of the cardboard to reflect the sun onto the bottle. After a few hours, you will see that the water become too hot without using electricity.