how many joules are needed to convert 312.0g of ice at -35.0 degrees C to liquid water at 25.0 degrees C.

Heat needed : 159.33 kJ

The heat to change the phase can be formulated :  

Q = mLf (melting/freezing)  

Q = mLv (vaporization/condensation)  

Lf=latent heat of fusion  

Lv=latent heat of vaporization  

The heat needed to raise the temperature

Q = m . c . Δt

The specific heat of ice is 2.09J/g°C; the specific heat of water is 4.182 J/g°C; the heat of fusion is 333.0 J/g.

1. heat to raise temperature from -35 °C to 0 °C  

2. phase change(ice to water)

3. heat to raise temperature from 0 °C to 25 °C  

Total heat needed :

22,828.8 + 103,896+32,604=159,328.8 J=159.33 kJ

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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~ trueboss72