This mug is made of two layers of glass separated by empty space. It is more effective than a ceramic mug at keeping the beverage warm. Why is this design more effective?

Heat moves from the warm beverage to the cooler surroundings by conduction, convection, and radiation. The empty space between the glass layers contains almost no particles, so it greatly reduces heat transfer by conduction and convection. That makes the double-layer mug better at keeping the beverage warm; the correct choice is “The empty space has no particles to transfer thermal energy.”

AI-written and checked against the verified answer.