1.Ice water has a lower density than liquid water, making it float. Describe why
ID: 6185 • Letter: 1
Question
1.Ice water has a lower density than liquid water, making it float. Describe why this property was essential for the development of life on this planet.
2. Unbuffered or weakly buffered basic solutions slowly become more acidic with time, unless they are stored in tightly sealed containers. Explain.
Explanation / Answer
For your first question, the ability of ice to float because of the expansion of water as it solidifies is an important factor in the fitness of the environment. If ice sank, then eventually all ponds, lakes, and even oceans would freeze solid, making life as we know it impossible on Earth. During the summer, only the upper few inches of the ocean would thaw. Instead, when a deep body of water cools, the floating ice insulated the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface. For the second question, air always contains small amounts of carbon dioxide which dissolves in water making it slightly acidic. So if you did not tightly seal containers that contain the unbuffered or weakly buffered solutions slowly they will become acidic because of the carbon dioxide in the air. This is how carbon dioxide changes the pH of water: 1. Carbon dioxide dissolves slightly in water to form a weak acid called carbonic acid, H2CO3, according to the following reaction: CO2 + H2O --> H2CO3 2. After that, carbonic acid reacts slightly and reversibly in water to form a hydronium cation, H3O+, and the bicarbonate ion, HCO3-, according to the following reaction: H2CO3 + H2O --> HCO3- + H3O+ This chemical behaviour explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air. I hope this has been helpful to you. Please rate if it is helpful. Thanks.
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