Putting Water in a Bottle
In the plastic bottle, pour some tap water which should be at room temperature. Do not fill more than ¼ of the total capacity.
Add Rubbing Alcohol
Now slowly add rubbing alcohol into the bottle that you filled with water. Keep on adding until you see the that the bottle is half full.
Inserting Plastic Straw
Slide a plastic straw inside the bottle and cover the opening of the bottle with the modeling clay. Make sure you adjust the straw at a level that it should not come in contact with the end of the bottle.
Attach Piece of Paper
Leave the apparatus for atleast one hour to get the liquid adjusted to room temperature. Attach a piece of paper with the part of straw that is outside and above the modeling clay junction.
Noting the Temperature
Place the bottle in the sun or anywhere else. As you note the reading of the bottle, there will be a rise in the liquid level which will be the same as the rise in a regular thermometer when measuring.