How do it know to keep hot stuff hot and cold stuff cold?

Question

I have a thermos and you put hot soup in it and it stays hot all day. If you put cold milk in it it stays cold all day. So , How do it know to keep hot stuff hot and cold stuff cold? Is there a thermos brain?

Answer 1

it stays at the tempeature of the item you put in it

Answer 2

The thermos is a great little device we can thank a man named Sir James Dewar for developing. Back around 1885 this guy was experimenting with some stuff called liquid gases and needed a way to keep heat away from them. So he set his mind to it and put together a container which was called, surprise, a Dewar flask. Well, once he saw how well this flask worked he started selling them to other people and called them a Thermos which means "heat".

Now a thermos is able to do what it does by utilizing a combination of physical and material properties to keep our hot chocolate hot and our ice tea icy. The three things we need to worry about when it comes to stopping heat from moving about are conduction, convection and radiation (You will have to look these up). Dewar figured if he could slow down these processes then he could keep the heat back.

Now here is what he came up with. A thermos has an inner container made of glass. This container is really like one bottle inside of anouther bottle and sealed at the ends by melting the edges together. They then take all the air out from the space between the two glass bottles to produce a vacuum. The reason they do that is because a vacuum is a terrible conductor of heat and does a good job at slowwing down the movement of heat by convection. Ok, we took care of convection, now lets do something about the other two. To slow down the heat moving by radiation they coat the facing surfaces of the glass bottles with a silvery solution (kind of like a mirror). This will reflect the heat radiation and help slow down any losses we might get that way. Thats two. For the last, conduction, they use a material like cork or rubber and these days even thermal plastic to make the bottle stopper and anything else that might touch the outside surface of the glass container. These materials are also bad conductors of heat and will slow down the heat moving via conduction. Ofcourse whats left is the part we can all see on the outside which can be metal or plastic and is the protective covering for the glass bottles.

Remember, the idea here (with the thermos) is to slow down the movement of heat from one place to the other. So if you have hot stuff in the thermos or cold stuff in the thermos, the end result is the same. Keep heat from moving to where you don't want it to go for as long as possible.

You asked a very good question that I'll bet alot of people never even thought about. A thermos is something we all take for granted these days and never stop to think about all the cool science going on inside when we use them.

Some of the key words you need to look up to better understand how the thermos works are: Conduction, Convection, Radiation and Vacuum.

Keep that coco warm and have fun.

Answer 3

The insulation properties of the thermos keeps hot and cold from getting in or out.

Answer 4

This flask must have an insulating wall. Dewar flasks have a wall that contains a vacuum. warmth can't flow a vacuum by technique of conduction (even in spite of the undeniable fact that somewhat warmth may destroy out by technique of irradiation). for this reason, warmth can't go away a warm liquid in a Dewar flask; and warm temperature can't enter a cold liquid from the exterior both. The flask does no longer could carry close some thing to provide this service.