[jcais]

If a beaker of chemicals is warmed using a hot plate, is this an exothermic reaction? I am thinking yes, because the beaker is giving off heat. When you place your hand near it, you can feel the heat through convection. Then again, the liquid is taking in heat to become warmer, and this seems endothermic.

If the chemical/liquid is cooled, is this indeed endothermic? I don't know. I don't think it is taking in heat from the surroundings because it is getting colder, not warmer. It might be exothermic because it is giving off heat in order to become cooler.

I am unsure about the above two situations. Can anyone help me? Thank you.

[Borek]

Doesn't matter what you do to the reaction vessel, what matters is if the reaction produces heat or not.

[Donaldson Tan]

jcais: are you describing a physical or chemical process?

[JZ_1]

Things (heat-wise) generally goes from Hot to Cold.

When you heat a beaker of water, the water is getting the heat from the hot plate.
When you are cooling it down, the water is giving off its heat into the suroundings.

When you put your hands on the beacker, it can go either way depending on which is cooler and which is warmer. If you're hands are warmer than the beacker of water, then the heat is going into the beaker of water; and vice versa.

I am not going to say which is endothermic or exothermic because is depends on if you are describing a physical or chemical process.

[Borek]

Things (heat-wise) generally goes from Hot to Cold.

No, they go from the temperature they have to the temperature of surroundings.

Put cold drink on your desk on the hot day. Will it get even colder, or will it get lukewarm?

[JZ_1]

Things (heat-wise) generally goes from Hot to Cold.

No, they go from the temperature they have to the temperature of surroundings.

Put cold drink on your desk on the hot day. Will it get even colder, or will it get lukewarm?

By Hot to Cold, I meant from a higher state of energy to a lower state of energy, not COLD. If you put a cold drink on a hot day, depending on the temperature and time it is exposed to the surroundings, the drink might get hot... if the "hot day" is over 50 degrees Celsius, which I doubt the day would come. But it still stands that the surrounding temperature. at least closer to the drink, would get cooler because it is going from a higher state of energy to a lower state of energy (getting cooler).

[Borek]

You have change your wording, but you are still wrong. Things go not from hot to cold, but to the thermal equilibrium. To do so one of the things must get colder while the second must get hotter (unless they were already in equilibrium). According to your original statement both things should get colder - which is obviously wrong.

[jcais]

I guess it would be a chemical process. We placed a beaker of liquid in another beaker of ice and water mixture for five minutes. The main liquid became cooler. I am thinking this is an endothermic reaction.

Thank you.

[Donaldson Tan]

There would be a change in the material composition if this is a chemical proces.

Unfortunately, only temperature change is achieved, so this is a physical process.

Heat is transferrd from the main liquid to ice-water mixture until both substances are at thermal equilibrium, ie. they are of the same temperature. The temperature of the main liquid decreases to the final temperature as it looses heat. The temperature of the ice-water increases (and some ice melts) as the ice-water mixture absorbs the heat.

I would think that the words exothermic and endothermic are not applicable to physical processes.

[Yggdrasil]

Here's a good way to think about it.  Endothermic and exothermic are tems which relate to (Delta)H, a quantity which is related to the chemical potential energy of the chemicals in a reaction.  Temperature on the other hand, is related to the kinetic energy of the chemicals in a system.  If you change the temperature by heating, you are changing the kinetic energy, but not necessarily changing the potential energy.  So, although you know what's happening to the kinetic energy of the system, you don't know whats happening to the potential energy of the system, so you can't comment on (Delta)H and whether the process is exothermic or endothermic.