Question

Why is melting of ice a better coolant than water at zero degrees celsius?

Answer 1

1. The amount of heat energy required to melt one kilogram of a solid ( $1g$ in the case of CGS system) at its melting point, without any rise in temperature is called the specific latent heat of fusion.
2. As we know $1kg$ of ice on meting absorbs $336000J$ of heat energy and $1kg$ of water for freezing will release $336000J$ of heat energy.
3. Therefore, latent heat of ice is $336000J$ for every $1kg$ ice.
4. Hence, changing ice at $0°C$ to water at $0°C$ will extract $336000J$ of heat from the hot engine and will cool the engine for a longer time.