Phase Changes

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Victoria Luu - 1C
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Joined: Fri Sep 28, 2018 12:15 am

Phase Changes

Postby Victoria Luu - 1C » Sun Jan 27, 2019 11:48 am

Why is melting and vaporization considered endothermic?

305113590
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

Re: Phase Changes

Postby 305113590 » Sun Jan 27, 2019 11:51 am

Melting is considered endothermic because heat is required to break the bonds in the solid ice to become liquid water. In a similar vein, heat is required to break the bonds in the liquid water to become gaseous particles. Both processes require an input of energy to allow the molecules to reach a more excited state. Endothermic reaction always require energy, while exothermic ones release energy

Alexa_Henrie_1I
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Joined: Fri Sep 29, 2017 7:03 am

Re: Phase Changes

Postby Alexa_Henrie_1I » Sun Jan 27, 2019 12:37 pm

Another way to determine whether a reaction is endothermic or exothermic is by the value of delta H: an endothermic has a positive delta H because the reaction is absorbing energy, whereas an exothermic energy has a negative delta H because it is releasing energy.

KatrinaPho_2I
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Joined: Fri Sep 28, 2018 12:28 am

Re: Phase Changes

Postby KatrinaPho_2I » Sun Jan 27, 2019 2:25 pm

To turn ice to water (melting), heat must be added to the system (endothermic). In ice, the molecules have very little movement, adding heat energy to this increases the kinetic energy of the molecules, pushing it through a phase change and melting into water. The same is true for vaporization where adding heat energy increases the movement of the molecules.

Margaret Akey
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Joined: Fri Sep 28, 2018 12:18 am

Re: Phase Changes

Postby Margaret Akey » Sun Jan 27, 2019 2:34 pm

exothermic reactions tend to occur spontaneously (since energy is released), which makes ice melting/water boiling endothermic because you have to put heat in to have a phase change. it does not occur spontaneously (no energy is released)

KarlaArevalo2F
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Re: Phase Changes

Postby KarlaArevalo2F » Sun Jan 27, 2019 9:10 pm

melting and vaporization are considered endothermic because molecules must be broken up using heat, the definition of being an endothermic reaction.

RachelCheung1A
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Joined: Fri Sep 28, 2018 12:19 am

Re: Phase Changes

Postby RachelCheung1A » Sun Jan 27, 2019 9:12 pm

They are both endothermic because they need to take in heat to break bonds and change phase

Edward Suarez 1I
Posts: 75
Joined: Fri Sep 28, 2018 12:27 am

Re: Phase Changes

Postby Edward Suarez 1I » Sun Jan 27, 2019 9:39 pm

both require the input of heat to transition into that state (heat needed to make a block of ice into water, and heat needed to make water into vapor)

think irl when u actually you leave ice out and it melts because of heat, or when you boil water


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