Make sure it s a fair test by keeping all the variables the same and only change the thing I am investigating. These are conduction, convection and radiation. Conduction is when something is heated the heat energy causes molecules at the heated end to vibrate violently, and each vibrating molecule causes nearby molecules to vibrate as well. In this way heat travels slowly through solids. Metals are good conductors of heat and plastic is a bad conductor of heat.
Convection is when heated fluids expand and so become less dense.
Convection is transfer of heat energy, within a fluid, by the circulation of the fluid due to temperature differences. The currents of moving molecules are called convection currents. Convection occurs in fluids because the molecules in solids are not free to move. Heat travels through the air by convection. If the heat is allowed to do these things the liquid is bound to cool down because the heat will be able to travel through the air by convection and the heated molecules will escape.