2006-07-14 08:27:37 · 12 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
an insulated bag does not actively heat or cool your food. it merely insulates your food, meaning it greatly reduces the amount of heat that either leaves or enters the system. if your food is hot and the ambient air temperature is moderate, then heat will try to move from your food to the ambient air (2nd law of thermodynamics). But the thermal conductivity of the walls of your bag is very low, so heat moves very slowly through the bag, i.e. your food stays hot. The same is true if your food is cold. Heat will try to move from the ambient air to the food, but the walls slow it down, keeping your food cold.
So in other words, your bag doesn't actually "know" anything, it just keeps the temperature of the contents constant for a longer time than they would be in a normal bag.
2006-07-14 08:30:48 · answer #1 · answered by Critical Mass 4 · 0⤊ 0⤋
Hi the bag insulates your hot food keeping the heat in for a while before it escapes through the material, eventually your food will go cold if you left it as all the heat will of escaped through the fabric.
2006-07-14 08:40:55 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The cold bag is an insulator, meaning that it preserves the temperature of whatever's in there, keeping hot things hot or cold things cold.
2006-07-14 08:32:00 · answer #3 · answered by bogusman82 5 · 1⤊ 0⤋
It doesn't "know". The bag is simply an insulator. It keeps the temperature inside the bag from being effected by the temperature outside the bag.
2006-07-14 08:31:04 · answer #4 · answered by PUtuba7 4 · 1⤊ 0⤋
It's just insulation, it maintains the temperature inside the bag, whether it's hot or cold.
2006-07-14 08:31:34 · answer #5 · answered by hex913 3 · 1⤊ 0⤋
Hot is fast moving molecules, Cold is slow moving ones. Your bag just keeping the fast moving molecules from interacting with slower (colder) ones. Thus it stays hot. When cold things are in the bag it does the same thing. It prevents these slower (colder) molecules from speeding up by interacting with faster (hotter) molecules.
2006-07-14 08:32:31 · answer #6 · answered by Bauercvhs 4 · 1⤊ 0⤋
It's the insulation that keeps the temperature in. So, really, it doesn't "know," that's just how it's designed, to keep the heat from escaping hot foods and to keep the cold from escaping cold foods.
2006-07-14 08:31:31 · answer #7 · answered by Manders 3 · 1⤊ 0⤋
It is not that it is a cold bag but thAT IT IS INSULATED...THEREFORE keeping the item as close to temp as possible
2006-07-14 08:32:01 · answer #8 · answered by johnnyquest 3 · 0⤊ 0⤋
cos i tell every bag that is made
i explain the facts of life to them
2006-07-20 10:19:08 · answer #9 · answered by itsa o 6 · 0⤊ 0⤋
it doesn't "know" it just keeps the fish and chips (your "system") from leaking heat into the rest of universe and vice versa.
2006-07-14 15:25:36 · answer #10 · answered by The Frontrunner 5 · 0⤊ 0⤋