Free STEM + AI learning resources · Ages 9–13

Does a refrigerator make cold?

A refrigerator keeps food cool by moving heat out of its insulated cabinet and into the surrounding room. That small change in wording opens up a much better design question.

An original companion activity from How Your House Thinks. About 10–15 minutes, on paper.

Start with the useful job

“It makes cold” describes how the inside feels, but not what the machine does. A more useful explanation is: “It uses energy to move heat from the inside to the room.” The insulation helps slow heat entering again.

You do not need to find or touch working parts. Use the book’s refrigerator diagram and a pencil. Different refrigerator designs have different parts and controls, so a diagram is a model, not a repair guide.

Draw two paths, not one mystery

1. Energy in: electricity powers the cooling system.
2. Heat moved: heat travels from the cabinet through the refrigeration system to the room.
3. Useful result: the inside stays cooler than the room under normal operating conditions.

Label each statement “shown in the diagram,” “explained by a source,” or “still a question.” It is fine to leave a question unanswered until you can check it.

Now imagine a door reminder

On paper, invent a reminder for a door that has been left open. Compare these ideas:

• A person checks that the door is closed.
• A door switch and timer trigger a reminder after a chosen delay.
• A proposed AI feature predicts when a reminder might be useful from patterns.

The timer option is automatic, but it does not need AI. Ask whether prediction adds a useful benefit to this particular job. What extra data, complexity, or mistakes would come with it?

Give your design a failure plan

Suppose the imaginary door reading is wrong. What happens next? Could the reminder be confusing? Who can dismiss it or ask an adult to check the problem? Discuss the scenario on paper only; do not leave a real refrigerator open or change its controls to test an idea.

Finish this sentence: “For this job, I would choose ___ because ___.” Choosing a simpler tool is a valid design decision.

Science reference: the U.S. Department of Energy explains heat transfer in heat pumps and refrigerators. Design options above are hypothetical teaching examples, not appliance modification instructions.