General Question

Nullo's avatar

Is the temperature in a room dependent on the room's contents? See details.

Asked by Nullo (21973points) January 13th, 2012

For the purposes of this exercise, let us assume that the room is at room temperature, and perfectly insulated; there will be no heat coming in from or escaping to the space beyond it.
Now let us introduce a block of ice into this hypothetical space, which subsequently melts.

Does the room’s temperature decrease in accordance with the amount of ice that was melted, and remain lowered as a result?

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13 Answers

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bongo's avatar

Have you never noticed that when a room is really full of people it warms up quickly because of all the body heat? This is exactly the same but in reverse. Yes the room would cool.

elbanditoroso's avatar

I believe that the room would get slightly cooler temporarily, until the ice block had melted (which it would). One the melting was completed and the water had warmed to the ambient temperature in the room, it would be revert back to the pre-ice block temperature.

However the relative humidity in the room would increase, again, temporarily, until the water from the melted ice evaporated.

ragingloli's avatar

With perfect insulation the the room temperature would be permanently decreased after the ice block has consumed part of the room’s thermal energy to turn into a liquid state.
The room temperature will not increase afterwards, because that would require additional energy from outside the system.

JLeslie's avatar

Yes, it would decrease in my opinion. Just like the old ice boxes, before refridgerators.

zenvelo's avatar

Yes, the amount of heat energy taken to melt the ice and raise the water’s temperature would equal the reduction in total heat energy in the room prior to the introduction of the ice. The equilibrium temperature would be lower than the original room temperature; the difference is dependent on the size of the block of ice.

I don’t remember the physics formulas, it’s been a while since I did one of these calculations.

PhiNotPi's avatar

Yes, the resulting temperature of the room depends on the amount of mass inside the room. The reason is that large heavy objects hold more heat energy at the same temperature.

The formula is something along the lines of this:
Total heat energy = temperature * total mass of everything in the room

This formula is not perfect, a perfect formula takes into account the properties of every object in the room.

From this we get:
Temperature = total heat energy / total mass

When you introduce the block of ice, you introduce some mass to the room but a very small amount of heat energy due to its temperature. I don’t know how to calculate the dispersion of energy from the ice, but luckily we are talking about the end state after that has occurred.

So,
New total heat energy = room temperature * room mass + ice temperature * ice mass

New temperature = new total heat energy / (mass of room + ice)

The new temperature depends on the mass an temperature of the room and the mass and temperature of the ice.

marinelife's avatar

Yes, it does. Suppose you have an oven going for example? Or you are running a bunch of computer equipment?

PhiNotPi's avatar

Things like ovens, lamps, people, and the like add a dynamic element to the mix.
Actually, having an oven or lamp connected to an outside power grid means that there is actually energy that is constantly coming into the room from the outside world. Since energy is always coming into the room and being partially converted into heat, and the heat generated cannot leave, then the room can and theoretically will heat up indefinitely.

For things like people that are not connected to the outside, then there will always be a gradual heating of the room due to the body heat of the person. The amount that the temperature goes up after any given period of time is governed by much more complicated equations than the ones above. The room will continue heating until the person dies.

LuckyGuy's avatar

Yes. All materials have a property known as Heat Capacity. It is a measure of how much energy it takes to raise the material a certain temperature. Compared with most solids the heat capacity of air is very small. If you have a room full of “stuff” the block of ice will not be able to pull the temperature down as far as it could if the same room was only filled with air.
Sometimes this effect is called thermal mass

john65pennington's avatar

I have an oil heater in one room. It does its job of heating one room.

This is the reverse of your hypothetical question and yes, the block of ice would have a slight and temporary cooling effect.

flutherother's avatar

The disparity in the temperatures of the block of ice and the rest of the room would even out, that is the ice will tend to warm and melt and the room will cool. When the temperatures are the same equilibrium has been reached and there can be no more change.

Nullo's avatar

Thank you all for your answers!

@PhiNotPi @john65pennington @marinelife The hypothetical room is a simple model to get a better grip on a concept. A first draft of the question went, “What becomes of the heat that melts ice?”

@LuckyGuy I tried explaining thermal mass to my boss once (I run ovens, which weren’t cooking fast enough for him), didn’t do well. It didn’t help that his experience with physics was limited to operating his car.

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