What happens to a wet sponge when you aim a fan at it? Water leaves the sponge faster than one sitting in still air. Temperature and surface area also play a role. You test each factor one at a time. Use sponges of different sizes to change surface area. Use hot and cold water to change temperature. Use a fan to add wind. A pan balance tracks how much water each sponge loses. The key rule is to change only one factor at a time. Everything else stays the same so the test is fair.