Why is melting endothermic

Unless otherwise specified, it is assumed that a boiling point is for 1 atm of pressure. To determine the magnitude of the energy change, we must first convert the amount of Br 2 to moles. As with melting, the energy in boiling goes exclusively to changing the phase of a substance; it does not go into changing the temperature of a substance.

So boiling is also an isothermal process. Only when all of a substance has boiled does any additional energy go to changing its temperature. What happens when a liquid becomes a gas? We have already established that a liquid is composed of particles in contact with each other. When a liquid becomes a gas, the particles separate from each other, with each particle going its own way in space. This is how gases tend to fill their containers. In a , the particles are a liquid; the particles are in contact but are also able to move around each other.

In b , the particles are a gas, and most of the volume is actually empty space. Under some circumstances, the solid phase can transition directly to the gas phase without going through a liquid phase, and a gas can directly become a solid.

The solid-to-gas change is called sublimation , while the reverse process is called deposition. Sublimation is isothermal, like the other phase changes. There are several common examples of sublimation.

A well-known product—dry ice—is actually solid CO 2. Dry ice is dry because it sublimes, with the solid bypassing the liquid phase and going straight to the gas phase. If you have ever noticed that ice cubes in a freezer tend to get smaller over time, it is because the solid water is very slowly subliming. The food is still good but looks unappetizing.

Reducing the temperature of a freezer will slow the sublimation of solid water. Chemical equations can be used to represent a phase change. In such cases, it is crucial to use phase labels on the substances. Husain A. Mar 12, Energy is gained. Note that it is NOT a reaction. Explanation: Water is a higher energy state, as the liquid can rotate and vibrate while solid ice can only vibrate. Post by Cyianna 2F » Tue Jan 09, am.

Post by kaushalrao2H » Tue Jan 09, am. Post by mayasinha1B » Wed Jan 10, pm. Laurence Lavelle Skip to content. Quick links. Email Link. Endothermic Reaction Post by Cyianna 2F » Tue Jan 09, am In lecture today, Lavelle mentioned the melting of an ice cube being an endothermic reaction.

I'm just a tad confused as to why this is? Join Clutch Prep Get a better grade with hundreds of hours of expert tutoring videos for your textbook Continue Continue OR Password must contain at least one uppercase letter, a number and a specific symbol. Problem : Why is melting ice an endothermic reaction? Problem Details Why is melting ice an endothermic reaction? Frequently Asked Questions What scientific concept do you need to know in order to solve this problem? What professor is this problem relevant for?

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