To determine which rock most likely fits the description given by the scientists, we need to analyze how different environmental conditions can affect rock weathering, both physically and chemically.
Given the environmental conditions for each rock:
1. Rock A:
- Intermittent rain showers
- Temperatures alternating between -2°C and 20°C
2. Rock B:
- Frequent acidic showers that contain carbonic acid
3. Rock C:
- Covered with algae and lichen
4. Rock D:
- Placed in an oxygen-rich environment
5. Rock E:
- Hot and dry environment
- Low temperature of 35°C
The scientists observed that one particular rock had large fractures and had split into two pieces, with its chemical composition largely unchanged. Let's analyze these conditions one by one:
- Rock A's environment has intermittent rain and temperature fluctuations between -2°C and 20°C. These conditions are conducive to physical weathering, especially freeze-thaw cycles, where water enters cracks; freezes and expands at lower temperatures (-2°C), causing stress and fractures within the rock. This can lead to the rock breaking apart physically over time. Importantly, this process does not necessarily alter the rock’s chemical composition significantly.
- Rock B is subject to acidic showers containing carbonic acid. This would likely lead to chemical weathering, affecting the rock's chemical composition over time.
- Rock C is covered with algae and lichen, which also promote chemical weathering as well as some physical weathering due to biological activity. The effect is likely more significant on the chemical composition as the organisms produce weak acids that break down minerals.
- Rock D is exposed to an oxygen-rich environment, which can lead to oxidation of minerals within the rock. This primarily represents a form of chemical weathering.
- Rock E is in a hot and dry environment with a relatively low temperature of 35°C. While high temperatures can cause some physical stress, these conditions are less likely to cause significant physical fracturing compared to freeze-thaw cycles.
Given that the rock's chemical composition remained largely unchanged while it developed large fractures, the most plausible scenario involves a physical rather than chemical weathering process, which points us to Rock A. The freeze-thaw cycles in Rock A's environment directly cause physical fracturing without significantly altering the chemical composition.
Therefore, the rock most likely to exhibit large fractures and split into two pieces due to physical weathering, while keeping its chemical composition largely unchanged, is:
A. Rock A
