Before Class on Monday, Oct. 24: Phase Changes and also Heats of Formation

Before class on Monday, Oct. 24,

Please watch the three videos below (12 min, 16 min, 14 min)
Complete the note packet labelled Lessons 3.3-3.4
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12 thoughts on “Before Class on Monday, Oct. 24: Phase Changes and also Heats of Formation”

What is the difference between the diamond state and all the other states?

Suzanne Irwin says:

October 23, 2016 at 6:57 pm

when carbon atoms exist as diamond, each carbon atom is bonded to 4 other carbon atoms. It is very strong structure. It is not the structure that carbon exists in most easily at 1 atm and 25 C. Some work has to be done to make carbon into diamond (usually it is put under great pressure in the earth–that is why diamonds are mined below the earth.) Carbon exists as graphite in its most natural state –meaning that each carbon atom bonds to 2 other carbon atoms, and the fourth bond is really a intermolecular force between one sheet of carbon atoms and another. This makes this type of carbon, which we call graphite, slippery. It is use in pencils and as a lubricant. We will be learning about the different types of solid structures for non metals and for metals in our next unit.

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When it’s melting, enthalpy of fusion is positive. When it’s freezing, the enthalpy of fusion is negative.

Why Is it important we recognize standard enthalpies of formation ? Will we have to guess for each element ? Or are there general rules to follow? Also , in example 1, will we always be given a chart when asked to find the enthalpy of reaction ?

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In this lesson, I learned about the enthalpy of phase changes and how to calculate it. I also learned about the heat of standard enthalpy/heat formation and how to calculate enthalpy of reactions using Hess’s Law and standard enthalpy/heat formation.

Question: – is standard enthalpy change the same as standard enthalpy of formation?
– is standard enthalpy of formation the same as enthalpy of formation?

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In this video I learned about calculating the enthalpy of phase changes, the heat of formation, what standard state is (25 C and 1 atm.), how to figure out if equations represented a standard enthalpy formation, and how to combine Hess’s Law and standard enthalpy change to find the standard enthalpy of a non-formation reaction.

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In this video, I learned about heat of formation and standard states. I also learned how to calculate enthalpies of reaction using enthalpies of formation.

Question: I was confused about standard enthalpy change and standard enthalpy formation. What’s the difference between the two? Also, is it required that we remember the summation formula or is just knowing how to do a problem like that fine?

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In this lesson, I learned how to calculate enthalpy of a phase change, heat of formation. I also learned standard enthalpy of formation and how to use enthalpy of formation to calculate enthalpies of reaction.

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In this video, we combined Hess’s Law and the standard state to calculate enthalpy

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I learned that heat of formation is the energy needed to make something from its basic element parts. This require the element parts to exist in a standard state at 1 atm and 25 C. To find the standard enthalpy of formation, I could find the sum of the product’s standard enthalpy formation – the sum of the reactants’ standard enthalpy of formation.

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