Final answer:
The example of an observation is (c) when a given sample of gasoline is burned in a closed container, the mass of the container and its contents does not change, demonstrating the law of conservation of matter.
Step-by-step explanation:
The question at hand is asking to identify which statement is an example of an observation. An observation is a statement based on something one has seen, heard, or noticed. Among the given options, the correct answer is (c) When a given sample of gasoline is burned in a closed container, the mass of the container and its contents does not change. This is a direct observation that exemplifies the law of conservation of matter, which states that matter is neither created nor destroyed in chemical reactions, resulting in the mass of the closed system remaining constant.
For example, during the brewing of beer, the input substances are transformed into beer with no loss in the total mass, illustrating that the sum of the mass of the ingredients equals the sum of the mass of the beer and the gases released. This observation is consistent with the fact that, in chemical reactions, matter is rearranged but its total quantity does not change, adhering to the conservation of matter.