does heat flow from hot to cold or from cold to hot?
342274
As my college chemistry professor said:\n\nOn a warm day, ther-mo-dy-nam-ics tells you that your cold beer is not going to get colder, it's going to get warmer so you better drink it sooner rather than later.\n\nThus, heat flows from hot to cold, not cold to hot.\n\nAnother way to look at it this.  Cold is not the presense of something, it is the absense of something.  It is the absense of thermal energy.  At absolute 0, there is now thermal energy in the system.  While placing something hot in the system will make the hot thing colder, it is because the thermal energy is migrating from the hot thing to warm up the cold surroundings.
802722
It is thermodynamic concepts. Where the high temperature resorvior heat energy transfer to low temperature resorvior (cool), that process known as absorbtion. It can be both way either heat or cool absorbing system.
112062
Heat conductivity? electrical?
180504
Heat is actually a microscale form of kinetic energy. The molecules of a hot object are in rapid motion; the hotter, the higher the average speed. If the object is gaseous the motion consists of free-path travel and collisions with other molecules. If it is liquid the paths between collisions are shorter, and if solid the motion is vibrational with no secular movement. \nIn conduction, heat is transferred by collisions between molecule populations with different average speeds. The transfer continues until both populations have the same average speed. \nIn convection, heat is transferred by mixing fluids of differing temperature. The mixing can be forced or driven by density differences caused by temperature difference. It is not necessary that molecular collisions occur in convection, since mixing alone changes the average molecular speeds.\nIn radiation, the molecular motion is converted to microwave or infrared energy by rigid motion of molecules or flexing of molecular bonds (ref.). Shorter wavelengths (light, UV, X-rays, gamma rays) are produced at higher temperatures where atomic electrons and nuclei may become involved. Radiative energy is not considered heat, but is converted to heat by absorption.
1159227
As a general rule, warm air rises and cool air sinks\nit expands and becomes lighter as the molecules of air move farther apart
624862
Convection is the mode of heat transfer in fluids (liquids and gases). Convection depends on the fact that, in general, fluids expand when heated and thus undergo a decrease in density (since a given volume of the fluid contains less matter at a higher temperature than at the original, lower temperature). As a result, the warmer, less dense portion of the fluid will tend to rise through the surrounding cooler fluid, in accordance with Archimedes' principle. If heat continues to be supplied, the cooler fluid that flows in to replace the rising warmer fluid will also become heated and also rise. Thus, a current, called a convection current, becomes established in the fluid, with warmer, less dense fluid continually rising from the point of application of heat and cooler, denser portions of the fluid flowing outward and downward to replace the warmer fluid. In this manner, heat eventually may be transferred to the entire fluid. Convection currents are widely observed in both liquids and gases. Many aspects of weather are connected with convection currents. For example, when a portion of the atmosphere becomes heated by contact with a warm area of land, it rises into the cooler, higher altitudes, with the result that some of the moisture carried with it may be condensed to form clouds and precipitation. Convection currents have been used for heating and ventilation since ancient times. Both hot-air and hot-water heating systems use convection to transfer heat through the entire structure being heated. Convection currents also assist in the ventilation of mines.
936508
Neither. Let's have a given that 1 fridge is empty and at 40 degrees inside. The other fridge is full and at 40 degrees. The room that these 2 fridges are in is at 70 degrees. The difference in temperature is the cause for heat to flow from hot to cold. The fridges have insulation that has a certain resistance to heat flow. The heat will flow through the walls of the fridges the same, so then Q(heat flow)=A(area)x(T1(70 degrees)-T2(40 degrees))/R(resistance). The area of heat loss for both fridges are equal,the resistance of both fridges are equal, the temperature differential for both is equal,  so the amount of electricity needed to keep the fridges at 40 degrees is equal.
606748
radiation\n\nbecause the above answer is correct...radiation is through AIR, not liquid\n\nconduction:  cold water cools you down, right?  conversely you heat the water\n\nconvection:  is specifically transfer of heat THRU LIQUID...so that works\n\ncondensation:  directly related to water vapor which is liquid, again
77449
Heat is the measure of internal energy that an object has.  Heat flows from a hotter object to a colder object only.  The internal energy flows from the higher level to the lower level.  This is similar to flowing water.  The water in a lake at the top of the hill has more potential energy than the water in the lake at the bottom of the hill.  The water will flow downhill only.  The water flows from the location where it has a higher energy level to the location where it can have a lower energy level.
509639
the cold water cools down the hot water, and the hot water warms up the cold water until they are at the same temperature....lukewarm water
621743
We cannot make a substance cold. \n\nWe can remove the heat from one place to another.\n\n  What is the difference between ice and water?\n\nFrom ice we have removed heat. The water is water because we have not removed heat from it. \n\nWe should not say ice is cold when compared to water, because we have not made it cold but we have removed heat from it.\n\nSimilarly when we want some hot coffee, we should ask, I want a coffee in which heat is added because we cannot make coffee hot.\n\nThank you.
306748
I am assuming the energy in this context as "heat energy". Then the answer is NO. It depends on the temperature.\n\nHeat flows from body of high temperature to body of low temperature.\n\nImagine a small tank (10ltr) on second floor and a big tank with 100 lt on first floor. If we connect these, water flows from top tank to below tank.\nHeight is synonymous to Temperature.\nAmount of water is synonymous to Heat energy.\n\nPS: Another similarity is electricity.\nTemperature = height of water = voltage\nheat flow = water flow = current\nheat energy = amount of water = charge\nheat resistance = pipe resistance = electrical resistance
89918
Convection and conduction are both important.  Radiation is negligible.  Heat is transported from the inside air to the refrigerant, and from the refrigerant to the outside air, through two heat exchangers.  In each exchanger, heat is transferred by a mixture of convection and conduction* between refrigerant and heat exchanger tubing, conduction through the walls of the tubing, and convection* (which may be forced by a fan) between the tubing and the air.  \n*Some may disagree with my interpretation of which kinds of heat transfer dominate each of these phases; it's a judgment call.  If most of the heat transfer is due to motion of the fluid (refrigerant or air) it's convection; if not it's conduction.
771899
When a solid is heated, the molecules become active and the bonds between them come looser, this is how a solid becomes a liquid.\nThe warmer the liquid becomes, the molecular bonds become even less connected and the liquid becomes a gas. (evaporation)\n\nWhen a gas is cooled, the molecular bonds change and they become tighter. or closer together causing the gas to turn back into a liquid (condensation).  And as the molecules become tighter still, then the liquid turns back into a solid.\n\nFreezing and melting points change per molecule.
683535
No. \nHeat will flow from an object that has more temperature to another with less temperature. An object having less temperature can have more thermal energy than another witj more temperature. This will depend on the mass of the object. See it this way: 1 gram of iron at 1000ºC has less energy than 1 ton of iron at 100ºC. Heat will flow from the object with less energy to the object with more energy in this case. But it will always flow from the object with more temperature.
1142068
In physics, heat is defined as energy in transit.Generally, heat is a form of energy associated with the motion of atoms, molecules and other particles which comprise matter. Heat can be created by chemical reactions (such as burning), nuclear reactions (such as fusion taking place inside the Sun), electromagnetic dissipation (as in electric stoves), or mechanical dissipation (such as friction). Heat can be transferred between objects by radiation, conduction and convection. Temperature, defined as the measure of an object to spontaneously give up energy, is used to indicate the level of elementary motion associated with heat. Heat can only be transferred between objects, or areas within an object, with different temperatures, and then only in the direction of the colder body.\n\n\nfor elaborate details refer to the link below:\n\nhttp://en.wikipedia.org/wiki/Heat
1089285
Conductivity does not depend on direction of heat flow.\n\nFound a paper on thermal conductivity see Fig 3