18.10:
Calorimetry
Calorimetry is the science of measuring the heat released and absorbed during a physical or chemical process under restricted conditions.
The principle of calorimetry implies that if two bodies are isolated from the surroundings, the heat gained by the cold body is equal to the heat loss by the hot body, i.e., their sum is equal to zero.
If 30 grams of ice cubes at zero degree celsius are dissolved in 150 grams of orange juice at 40 degree celsius, what would be the final temperature of the liquid after all the ice is melted? The specific heat of juice and ice is 4190 J/kg.K and 2100 J/kg.K, respectively, and the heat of fusion of ice is 334×103 J/kg.
First, list the known and unknown quantities.
Now apply the principle of calorimetry to juice and ice.
Rearrange the terms to find an expression for final temperature.
Substitute the values to calculate the final temperature of the orange juice, which is 21.86 degree celsius.
18.10:
Calorimetry
When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A container that prevents heat transfer in or out is called a calorimeter, and the use of a calorimeter to make measurements is called calorimetry. Generally, these measurements involve heat or specific heat capacity. The term "calorimetry problem" is used for any problem where the specified objects are thermally isolated from their surroundings. An important objective in solving calorimetry problems is that during a heat transfer between objects isolated from their surroundings, the heat gained by the colder object must equal the heat lost by the hotter object due to the conservation of energy.
For example, consider a cup of water poured into a hot aluminum pan placed off the stove. Here, the pan is placed on an insulated pad, and heat transfer to the air is neglected in the short time needed to reach equilibrium. As a result, this is a calorimetry problem, even though no isolating container is specified. Originally, the pan and water were not in thermal equilibrium. The pan is at a higher temperature than the water. Heat transfer restores thermal equilibrium once the water and the pan are in contact; it stops once thermal equilibrium between the pan and the water is achieved. The heat lost by the pan equals the heat gained by the water, which is the basic principle of calorimetry.
Suggested Reading
- OpenStax. (2019). University Physics Vol. 2. [Web version]. Retrieved from https://openstax.org/details/books/university-physics-volume-2; pp 24-25.