Experiments have shown that the quantity of thermal energy Q that is absorbed or

Question

Experiments have shown that the quantity of thermal energy Q that is absorbed or released while an object changes temperature is proportional to the mass m of the object and the temperture difference Delta T = T_final - T_initital: where c is the specific heat capacity, a quantity that is characteristic of the material. When two objects, one at higher temperature and one at lower temperature, are isolated from their surroundings and brought into thermal contact, energy conservation implies that the heat transferred from their surrounding and brought into thermal contact, energy conservation implies that the heat transferred from the hotter object is equal to the heat absorbed by the cooler object where the subscripts h and c refer to the hotter and cooler object, respectively. Equipment: Front of room: Balances, paper towels, metal pieces (unknowns), aluminum pieces At each table: Steam generator, temperature sensor, styrofoam cups Caution: The steam generators arc hot, so take care and handle the metal pieces only with the attached thread. Procedure: Fill the steam generator with water and place an aluminum piece in it. Heat it until the water boils. Fill a styrofoam cup half full of cold water, measure its temperature, and, when the aluminum piece is at the temperature of boiling water, transfer it to the cold water. When the system has reached equilibrium determine m_h Delta T_h versus m_c Delta T_c for this trial; here h (hot) refers to aluminum and c (cold) refers to water. Repeat the procedure at least three more times with different amounts of cold water. Then use Excel to construct a graph of m_h Delta T_h versus m_c Delta T_c. Record the number of your unknown sample and repeat steps 1. and 2. for this sample. Use the table on the next page to identify your unknown sample. How can you improve the experimental procedure so that you can identify the unknown sample with more confidence? Suggest several improvements and explain how they would decrease the experimental uncertainties.

Explanation / Answer

Firstly, the following experiment should be conducted under well insulated environment, otherwise there will be heat to the environment by aluminum and will be less heat available for the cold water, which results in less rise of temperature of the cold water water.

Secondly, when the hot aluminum comes in contact with the cold water, the water starts vaporising due to latent heat, which results in loss of mass of cold water during the experiment

So, the experiment should be perfomed in closed and well insulated chamber to avoid the above mentioned losses.

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