Why do fish die when placed in a tank filled with water that has been boiled and then cooled?

Verified step by step guidance

1. Understand that boiling water removes dissolved gases, including oxygen, which is essential for fish survival.
2. Recognize that when water is boiled, the dissolved oxygen is driven out of the water as the temperature increases.
3. Note that even after the water is cooled, the dissolved oxygen levels remain low because the gases do not readily re-dissolve back into the water.
4. Consider that fish rely on dissolved oxygen in the water to breathe through their gills.
5. Conclude that without sufficient dissolved oxygen, fish cannot survive, leading to their death in such an environment.

Key Concepts

Dissolved Oxygen

Dissolved oxygen is crucial for aquatic life, as fish rely on it for respiration. When water is boiled, the heat causes a significant reduction in the amount of dissolved oxygen, which can lead to hypoxia (low oxygen levels) when the water cools. If the oxygen levels are insufficient, fish cannot survive.

Temperature Effects on Solubility

The solubility of gases in liquids is affected by temperature; generally, warmer water holds less dissolved gas than cooler water. When water is boiled, it loses most of its dissolved gases, including oxygen. As the water cools, it does not regain the same levels of dissolved oxygen, making it unsuitable for fish.

Water Quality and Chemical Composition

Water quality encompasses various factors, including pH, hardness, and the presence of harmful substances. Boiling water can alter its chemical composition, potentially removing beneficial minerals and introducing harmful compounds. This change can create an inhospitable environment for fish, contributing to their death.