Question

Heat Transfer – In a Minute
Read the scenarios. Answer the 2 questions below.

1. Residents in Conyers, Georgia, woke up to 27 degrees weather. Ms. Ausby had to let Snoopy outside to go potty. When she opened the patio door, she immediately realized just how cold it was outside. Explain if the cold air from outside entered the house, or if the warm air from inside the house exited. How do you know?

2. Flat Shoals Elementary took their first-grade students to the zoo. The students were studying cold blooded animals. Their first stop was the reptile area. In the reptile exhibit, students noticed that an alligator was lying in the mud in a sunny area. Melissa said that her per turtle lays on his "sun" rock like the alligator. Explain the method of heat transfer that the alligator and the turtle were using to warm their bodies. How do you know?






p

Answer 1

1) Both happen, but the immediate sensation is cold air coming in. When the door opens warm indoor air begins to flow out and colder outdoor air flows in at the same time. This exchange is driven by convection and differences in air density (cold air is denser and tends to sink, warm air is lighter and rises), so you often feel a cold draft as the outside air pours in along the floor while some warm air escapes higher up. Heat is being transferred from the warmer indoor air to the colder outside air.

2) They are mainly using radiation to warm up. The sun sends energy as electromagnetic radiation (visible and infrared); the alligator and turtle absorb that radiant energy and their body temperatures rise. In the turtle’s case, conduction also helps because it’s lying on a warm rock—the rock transfers heat directly into the turtle where they touch.