why is an ice bag at 0 degrees centigrade a more effective coolant than water at 0 degrees centigrade?

Answer 1

For some purposes, a bag of ice is less effective, actually. If you need to cool something quickly, cold water is better than ice, because the contact between water and object is more complete than between ice and object. For best results, though, a mix of ice and water and salt works fastest. The salt lowers the freezing/melting point, so presuming your ice started out below 0, the whole mixture will stay below 0 as well.

Answer 2

Because making the transition from solid to liquid involves a phase transition which requires 334 Joules of energy (called the 'latent heat of fusion') to convert 1 gram of ice at 0 C to 1 gram of liquid water at 0 C. But the specific heat of liquid water is 4.2 Joules per gram (called the 'heat capacity' or 'specific heat') to change its temperature by 1 C. Essentially, the 'breaking up' of the ice crystal lattice requires energy (to go from solid to liquid) and it's this large difference in the amount of heat required that gives ice its superior cooling qualities.

Doug

Answer 3

Transition period.

Ice turns to water through this period at 0 C.
After the transition period the water must heat up.

The best way to cool something is by having as large of a temperature differential as possible. As water heats up, your differential decreases, so you loose cooling power.

Answer 4

When ice melts it absorbs heat,the water merely warms up.
So the ice pack turns to water while absorbing heat then the water continues from there.

Answer 5

authentic, yet there are different factors, including humidity, which influence it. 'Centigrade', as a length, relies on the properties of water. 0 is freezing factor, a hundred is boiling factor.

Answer 6

Heat of fusion.

When you add heat to water at 0C, it warms up.

When you add heat to ice at 0C, it melts some of the ice, but it stays at 0C.