1. Lavoisier and the Ice Calorimeter. Antoine Lavoisier and French mathematician LaPlace designed an apparatus called an ice calorimeter to measure heat released in various combustion reactions including animal respiration processes. Animals were placed in the calorimeter and the amount of ice melted was compared to the amount melted as charcoal was burned in a similar calorimeter. Oxygen intake and carbon dioxide (fixed air) production were also recorded and compared to the ratios of these two gases involved when the charcoal burned. Lavoisier and LaPlace concluded that the combustion of food in the animalÕs body supplied the heat to maintain its body temperature much as burning charcoal released heat through its oxidation.
2. Joseph Black and Latent Heat. In the 18th century it was commonly believed that when ice or snow reached its melting point, only a small addition of heat was necessary to convert the solid into liquid water. Joseph Black, a Scottish chemist, conducted a series of experiments which indicated that once ice began to melt, the temperature of the ice/water mixture remained constant so long as any ice remained. He calculated that the amount of heat necessary to melt ice was about 80% of the heat necessary to raise that same water from the freezing point to the boiling pointÑby all measures not a small amount of heat. Black coined the term Òlatent heatÓ (hidden heat) to refer to this heat which entered the ice/water mixture without raising the temperature.
Black went on to show that absorption of a substantially larger amount of heat occurred in a similar fashion as water was converted to water vapor. These findings were subsequently applied by fellow countryman James Watt as he improved Thomas NewcomenÕs steam engine by designing a separate chamber in which to condense the waste steam from the steam engine.
5. Word Search (see Appendix for master copy)
Words about the concepts in this module can be obtained from the clues given. Find these words in the block of letters:
1. This quantity is exerted by a gas that is in equilibrium with its liquid state at a given temperature (2 words).
2. Temperature at which a liquidÕs vapor pressure equals the atmospheric pressure (2 words).
3. Energy that is released but not apparent since it goes toward changing phase (2 words).
4. The quantity of energy that a given object can absorb per degree Celsius change in temperature (2 words).
5. What generally occurs when solid materials are heated due to increased kinetic energy of the particles.
6. Volume change that normally takes place when materials are cooled due to lower kinetic energies of the particles.
7. Type of bond that gives water its unusually high boiling point.
8. Adjective describing liquid that has a high vapor pressure and readily evaporates at room temperature.
9. The temperature at which a solid changes to its liquid form (2 words).
10. Common name for CO 2 (s) (2 words).
Answers: 1. VAPOR PRESSURE 2. BOILING POINT 3. LATENT HEAT 4. HEAT CAPACITY 5. EXPANSION 6. CONTRACTION 7. HYDROGEN 8. VOLATILE 9. MELTING POINT 10. DRY ICE
6. See cartoons at end of module.
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