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 materials, which block heat movement. Sometimes insulators are there to prevent heat escaping from food e.g. soup containers. Sometimes insulators are there to prevent heat from getting to food e.g. the padded lunch bag keeps a sandwich cooler.
Students draw their lunch bag, and the insulators they found, 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.
Metal soup containers have a layer of air between two walls. Air does not conduct heat so well, so prevents heat from rapidly leaving the soup container.
Silver-lined bags reflect heat (by another heat transfer process called “radiation”).