Tell students that they are going to do an experiment. They are going to put one doll in a sunny place and the other one away from the sun. Discuss steps of an experiment. Tell students that there are several parts of doing an experiment. Prediction and observation are two parts.
Observation means watching for any changes.
Students make predictions and observations. Point out that both dolls look exactly the same. Ask students for their predictions. After a few days, compare the dolls and have students make observations. Revisit students' predictions and see if they were correct.