How can a cup of water decrease in temperature? please answer my question in a scientific method, the questions will be below.

Step 1: Observation

Step 2: Research:

Step 3: Hypothesis:

Step 4: Experiment – explain the experiment that you would perform

Step 4a- The control variable

Step 4b- The dependent variable

Step 4c- The independent variable

Step 5- What do you predict the conclusion to be?