Two equestions?

Question

1. If you add a few chunks of ice to a tstyrofoam container with water and do not stir it, then teh temperature of the mixture would be significantly higher than the expected 0 degrees C. Please explain what is happening.

2. Two objects are made from the same material. They have different masses and temperatures. If the two are placed in contact, will they experience the same temperature change.? if not, then which object will experience the greater temperature change?

Answer 1

1. You would not expect the temperature to be 0 degrees C. The reason the temperature is higher is because although some heat has moved from the water into the ice, causing it to begin to melt, it has not been a sufficient amount of heat for the temperature of the water to fall to 0 degrees C. If you expected the temperature to be 0 degrees C, you would be misinterpreting the fact that a mixture of water and ice may be in thermal equilibrium at 0 degrees C. If a container of ice is allowed to melt, then the temperature of the mixture should be 0 degrees C at any point when water and ice exist in the container at the same time. This is not true when you add ice to water at a temperature greater than 0 degrees C.

2. The less massive object will experience a greater temperature change. Whichever object is colder, it will gain a total amount of heat energy equal to the amount of heat energy lost by the hotter object. However, the amount of heat energy gained or lost by each object is equal to the product of the temperature change of the object, the mass of the object, and the specific heat capacity of the object. Therefore, if the objects are made from the same material, a less massive object must have a greater temperature change in order for its change in heat content to be equal to that of the more massive object.

Answer 2

You have already received an adequate answer, but I'll expand a little.

1. If the water in the insulated container is warmer than 0º C, then its heat will be used to melt the ice. If there is enough ice, you will end up with a mixture of water and ice at 0º C. Otherwise, the water will be cooled, but not to 0º C. A point that was not made is that if the mixture of water and ice is not stirred, the water near the ice will be cooler than the water that is further away.

2. Your other answer is correct. The bigger mass, since it has the same specific heat, will have a smaller change in temperature than the little one. Consider a pellet at 100º C coming into contact with a bowling ball at 20º C. The pellet will be cooled quickly to 20º C, while the increase in the temperature of the bowling ball will be too small to measure.