In this question, we are asked to identify the statement that is not correct. Let`s analyze each option to understand which one is incorrect.
Option 1: Water starts boiling when its vapor pressure becomes equal to atmospheric pressure. This statement is correct. Boiling occurs when the vapor pressure of a liquid equals the atmospheric pressure acting on it.
Option 2: Water is known as the universal solvent. This statement is generally correct. Water has the ability to dissolve a wide range of substances, which is why it is often called the universal solvent. However, it is not always able to dissolve every substance.
Option 3: Permanent hardness of water is due to the presence of MgCl2, CaCl2, MgSO4, and CaSO4. This statement is correct. Permanent hardness of water, which cannot be removed by boiling, is caused by the presence of certain minerals such as magnesium chloride, calcium chloride, magnesium sulfate, and calcium sulfate.
Option 4: Density of ice is greater than that of water. This statement is incorrect. The density of ice is actually less than that of liquid water. This is why ice floats on water. When water freezes, the molecules form a lattice-like structure, causing the density to decrease.
In conclusion, the incorrect statement