Heat and insulation in lunch bags

Students get out their lunch bags and open them up. They look at the containers and the bag itself, to find insulating/reflective materials, which slow down heat movement.
Heat always moves from a hotter object to a cooler object. Lunch bags and food containers are designed to either keep heat in food that needs to stay warm, or away from foods that need to stay cool.
Students draw their lunch bag, and the insulators they found, optionally on the “Lunch bag insulation” worksheet (attached below).

Examples:
Anything padded or thick plastic (lunch bag itself, plastic containers, thick wrapping) does not transfer heat well, so will block heat from getting into food that needs to stay cold, or keep heat in food that needs to stay warm.
Metal soup containers and thermos flasks have a layer of air between two walls. Air does not conduct heat so well, so slows down heat leaving the container.
Silver-lined bags reflect heat (by a heat transfer process called “radiation”), so keep heat inside a container, or keep heat away from things that need to stay cool.