Everything gives out heat
A hot pan cools by radiating heat.
A hot utensil
A hot utensil is kept away from the flame. After some time it is no longer hot.
Where did its heat go?
What this lesson covers
The idea
All objects radiate heat and exchange heat with their surroundings by radiation, which is how a hot object left away from a source of heat cools down.
A hot utensil
A hot utensil is kept away from the flame. After some time it is no longer hot.
Where did its heat go?
- Out into its surroundings
- Back into the flame
- It vanished
Let the pan cool
Move the pan away from the flame. Then tap the three objects to see their heat arrows.
Out and in
The pan cooled down by radiating heat to its surroundings. Every object does this. Each object also takes in heat from its surroundings. The pan sent out more than it took in, so it cooled.
All objects radiate heat and exchange heat with their surroundings by radiation. This is how a hot object left away from a source of heat cools down.
Notes
All objects radiate heat and exchange heat with their surroundings by radiation, which is how a hot object left away from a source of heat cools down.
Check yourself
A hot utensil kept away from the flame cools down by …
Which objects radiate heat?
A hot pan sends out more heat than it takes in. What happens to the pan?
A glass of cold water takes in more heat from its surroundings than it sends out. What happens to it?
- radiating heat to its surroundings — correct. Yes!
- taking heat from the flame. The utensil is away from the flame. It gives heat to its surroundings.
- making cold. Cold is not made. The utensil loses heat by radiation.
- Only hot objects. Every object radiates heat. A hot object just gives out more.
- All objects — correct. Yes!
- Only the Sun. The Sun does it, and so does every other object.
- It gets even hotter. If it sent out less than it took in, it would warm up.
- Nothing happens. More heat leaving than coming in means the pan cools.
- It cools down — correct. Yes!
- It warms up — correct. Yes!
- It gets colder and colder. It takes in more heat than it gives out, so it warms.
- It stays at the same temperature. It would stay the same only if heat going out equalled heat coming in.