Question

The melting point of solid substances is directly proportional to pressure acting on them. However, ice-melts at a temperature lower than its usual melting point, when the pressure increases. This is because :

• A. Ice is not a true solid
• B. The bonds break under pressure
• C. Ice is less dense than water
• D. Pressure generates heat

Answer 1

The correct option is C Ice is less dense than water

The given question statement asks about that which among the given options correctly proves the reason behind ice-melts at a temperature lower than its usual melting point, when the pressure increases. About the melting point we can say that it is the point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. It is observed that at the melting point the solid and liquid phase exist in equilibrium. Generally, the melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or $100kPa$.
With an imminent increase in the value of pressure, we get that the melting point of ice will gradually decrease (i.e. ice melt) due to the less density of ice than that of water. The phenomenon which is concluded above is called regelation and is commonly used in ice-skating. Therefore, by the given facts we get that the correct option is the one which states that the ice is lighter than water.
So, the correct option would be option (C), ice is less dense than water.