Final answer:
Pinhole leaks in containers are typically identified by visible changes or evidence of leaking substances, such as spots of liquid, mold growth, and changes in water levels.
Step-by-step explanation:
Pinhole leaks in containers can usually be detected by the presence of visible signs, such as spots of liquid or a change in the physical state of the material outside the container. In the context of soup contamination, the contaminants are likely due to microbial activity, detectable by changes like mold growth or unpleasant odors.
For a water container that develops a hole below the water surface, the presence of a leak could be identified by a stream of water shooting out or a decrease in water level over time. Variations in pressure can also lead to detection of leaks, as changes in the flow of contents may indicate a breach in the container.