Final answer:
The decomposition of urea by bacteria in a urine sample causes the urine to develop an ammonia odor due to the breakdown of urea into ammonia, which can also make the urine more alkaline.
Step-by-step explanation:
The decomposition of urea by bacteria in a urine sample left at room temperature over 2 hours causes the urine to develop an ammonia odor. This is due to the breakdown of urea into ammonia by the enzyme urease, which is produced by bacteria. During this process, ammonia is released as a byproduct of the decomposition of nitrogen-containing organic compounds. Ammonia, being a basic compound, raises the pH of the surrounding environment, thus potentially making the urine more alkaline. Furthermore, in mammals, the urea cycle normally converts toxic ammonia to less toxic urea for excretion. When urea breaks down into ammonia outside the body, the characteristic ammonia odor develops.