When heating cold water, when the temperature has not reached the boiling point, why do bubbles often appear in the water? Why do the fish in the fish pond always approach the water surface when the w

When heating cold water, when the temperature has not reached the boiling point, why do bubbles often appear in the water? Why do the fish in the fish pond always approach the water surface when the weather is sultry? Because water can dissolve a small amount of gases, such as oxygen and carbon dioxide. The solubility of gas in water is regular, which decreases with the increase of temperature and increases with the increase of air pressure. Therefore, when heating, due to the decrease of gas solubility, it escapes from water in the form of bubbles. When the weather is sultry, the temperature is high and the air pressure is low, and there is little dissolved oxygen in the water, so the fish will cling to the water surface because of insufficient oxygen supply.