Evaporation is a process that involves water transforming from a liquid into water vapour, a gas. When human beings sweat, the liquid evaporates, carrying the heat away from the body and cooling it down. This process can also be used to cool down material objects. In this science experiment, the process of evaporation is used to prevent chocolate-covered sweets from melting.
Materials and hypothesis
This evaporation experiment uses foil-wrapped, chocolate-covered peppermints, which can be found at many corner shops and Pick n' Mix. You also need a variety of basic materials for the experiment. Alongside a notebook, timer and pencil, which you will use to record observations, gather three sheets of paper towels, scissors, a small bowl, a ruler, room temperature water and a desk lamp with a 60-watt bulb. The height of the desk lamp should be adjustable. Before beginning your experiment, devise a hypothesis, or prediction, about whether you believe that the sweets wrapped in a wet paper towel or in a dry paper towel will melt the fastest.
Begin your experiment by cutting the sheets of paper towels into 3.7 cm (1.5 inch) thick strips. Dip one paper towel strip into a bowl of room-temperature water, and wring it out; wrap one foil-covered peppermint in this paper towel strip, and another in a dry paper towel strip. Place the wrapped sweets underneath a desk lamp, and adjust the lamp so that the bulb is between 2.5 and 5 cm (1 and 2 inches) away from the sweets. Once 10 minutes has elapsed, remove the sweets from underneath the lamp, and unwrap the paper towel and foil coverings. Record what has happened to the peppermints in your notebook, such as whether the chocolate wrapped in the wet, or dry, paper towel has melted. Repeat this process twice more with new sweets and paper towel strips. Observe the similarities between the trials and whether the hypothesis you devised earlier is correct.
According to the Science Buddies website, the process of evaporation prevents the chocolate-covered peppermints wrapped in a wet paper towel from melting. In a similar fashion to when the human body sweats, the energy produced when the water evaporates from the damp paper towel cools the sweet down. The chocolate-covered sweet wrapped in the dry paper towel will melt underneath the desk lamp's hot light bulb.
Try using a thermometer to determine the beginning and end temperatures of the chocolate-covered sweets, which will help to demonstrate how the wet paper towel keeps the sweets cooler than the dry paper towel. You can also investigate how setting a fan on the sweets while they are underneath the desk lamp impacts the final results.