Heats of Reaction and Hess's Law

Heats of Reaction and Hess's Law

By: Grace Kilpatrick

Hi everyone! I hope you all are having a wonderful Thursday! Here is how class went today...

-First, Mrs. Friedmann checked in last night's homework. This was the Hess's Law-Practice worksheet and the Hess's Law worksheet, both which can be found in the Unit 8 Handouts folder. Due to time constraints, we did not have time to go over these in class. However, it is part of the homework to check the answer key to these worksheets, which is labeled as 5_Key_to_Hesss_Law_HW.pdf in the Unit 8 Keys Folder.

-Next, we went over the Heats of Reaction and Hess's Law pre-lab. These are the notes:

-For the rest of the period, we worked with a partner to collect experimental data for the Heats of Reaction and Hess's Law Lab. Mrs. Friedmann has uploaded lab data to use if you were absent in the Unit 8 Labs and Activities. This is my group's data. The upper portion is that data collected for reaction #1, where the lower portion is that data collected for reaction #2.

HOMEWORK:

-Check last night's homework with the answer keys online.

-See Webassign for the "Chapt. 9.1-2 - Solids and Liquids - Rdg Sheet" assignment due March 4th, at 11:59 PM

-Begin working on write up for today's lab-likely to be due Tuesday.

The next blogger will be...Juliette O.!

Hess's Law

Hess's Law

Today we went over Hess's law. Mrs. Friedmann's thorough and very helpful notes on it can be found here.

Tonight's homework is a webassign if you didn't do it yesterday (due tonight at 11:59) and three handouts on Hess's law (really two, but one is two pages). The first can be found here and the second here, but neither of them can be found here.

The net blogger is: Grace K!

Thermochemistry and Phase Diagrams (2/24/14)

Today in class, we reviewed and went over the answers to the packet Mrs. Friedmann gave us in class on Friday.  After going over the packet, we started to take notes on Phase Diagrams.  Mrs. Friedmann said that the packet and notes would be on Moodle.  Our homework was to do the two worksheets we picked up in class on Phase Diagrams.
The next blogger is Brandon M.

Thermochemistry - Putting Some Pieces Together

Thermochemistry - Putting Some Pieces Together

February 21st, 2014

Hayden Northwick

Today Mrs. Friedmann wasn't here, so we worked on a packet during class.  If the packet isn't finished by the end of class, it is homework.  Also the last two WebAssigns are re-opened for the duration of the weekend.  They close on the 23rd at 11:59PM.

The next blogger is:
Peter

Heats of Formation

Scribe Post Author: Serene P.

February 19, 2014

Starting off class today, there was no homework to be checked in. Ms. Friedmann reminded us of our homework and informed us that we should do our best to complete our lab calculations independently.  Our homework due tomorrow includes:

Heats of Formation worksheet(with using the two sheets of Thermodynamic Data)

Webassign 8.3-8.4 due by 11.59 tonight

Watch a video Ms. Friedmann posted on moodle. http://vimeo.com/59855650 This will go over the two prelab questions for the lab to be performed tomorrow in class. If you are to be absent, here is the link to the worksheet of the lab with data. http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/1314_Unit_8_--_Thermochemistry/Unit_8_Labs_and_Activities/2.19_Heat_of_Formation_Lab_with_Data.pdf

Heat of combustion lab write-up due tomorrow

During class today, we took notes on Heat Formation. Here are the notes: (Sorry! The diamond shaped figures with question marks in them were supposed to be triangles. I don't know how it occurred to be like this on the blog. Sorry again!)

Heats of Formation

4 NH3(g) + 7 02 → 4 NO2(g) + 6 H2O(l)

🔺H rxn= -1396KJ

4 NH3(g) + 7 O2 ---> 4 NO2(g) + 6 H2O(l)

*🔺H f (heat of formation) = The energy it takes to ‘form’ a COMPOUND from the elements that make it up.

*🔺H f often times, it’s exothermic. Sometimes its positive!

*🔺H f of an element (in its stable state) = 0KJ/moles

Examples: Na, H2, O2, Mg...etc.

*Units are KJ/moles

------------------------------------------------------------------------------------------------------------------

🔺 H reaction= sum of 🔺H f products - sum of 🔺 H f reactants

🔺 H reaction= (4 moles x (+33.2 KJ/moles)) + (6 moles x (-285.8 KJ/moles)) - (4 moles x (-46.1 KJ/moles)) + (7 moles x (0 KJ/moles))

=(132.8 KJ - 1714.8 KJ) - (-184.4 KJ)

=-1582KJ + 184.4 KJ

= -1397.6 KJ

Here is a picture of the Thermodynamic Data (Please remember that not all data tables of these values will be identical):

After completing out notes for the day, Ms. Friedmann gave us time to work on our homework. We may look forward to completing another lab tomorrow that will not require a complete write-up but will have post-lab questions to be completed.

Thanks!

Next Post Author: Hayden

Lab: Heat of Combustion

Lab: Heat of Combustion

2/18/2014:

           After Mrs. Friedmann checked in the homework, we went over the pre-lab questions (blue sheet). Some of these questions were new to the unit and proved to be challenging. The key to these questions can be found on moodle here. We then moved on to the lab for today.

The Lab:

           The Heat of Combustion Lab involved hanging a can of water over a burning candle, all inside a calorimeter. Some of the data we kept note of was the difference in water temperature and the difference of candle mass. For the purposes of the lab write-up, we are basing our calculations on the assumption that all the heat lost by the candle was gained by the water. Since our heat formula can't be used for the heat energy of the candle, we were told to instead find the heat gained by the water and assume this was the same as the heat lost by the candle. 

          For this lab, we will also need to use a formula for the combustion reaction that took place. This should include heat as one of the products and the use of C25H52 (paraffin) for the candle.

The homework for tonight is:

1) The lab write up is due Thursday

2) There is a new webassign due by Wednesday night

Tomorrow's scribe is:

Serene P.

2/14/14

Thermochemistry and Other Long Words

By: Kevin Mihelic

We started class by collecting a valentines day gift from Mrs. Friedmann. This gift was filled with baking soda and vinegar and to inflate it we had to step on it. I had some trouble with this. We picked up 3 sheets. One was a lab, one was a sheet of calculations to do for homework. The homework due on Tuesday is:

1. Check Fridays homework with key posted on moodle.
2. WebAssign on heating curves
3. Finish Calorimetry pre-lab (blue sheet) -- find on moodle
4. Watch video on Enthalpy video on moodle and take notes.

For notes on Energy Diagrams and Activation energy click here- http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/1314_Unit_8_--_Thermochemistry/Unit_8_Notes/2.14_Notes_on_Energy_Diagrams_and_Enthalpy.pdf

For the key to fridays homework here- http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/1314_Unit_8_--_Thermochemistry/Unit_8_Keys/Key_to_Heating_Curve_Calcs_Ws.pdf

For the Calorimetry prelab- http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/1314_Unit_8_--_Thermochemistry/Unit_8_Handouts/2.14_Heat_of_Combustion_Pre-Lab.pdf

On this sheet there are two difficult problems. These problems will be discussed in the comment section below this post. Please help even if you have trouble doing it- anything can help.

Fingers crossed for no school tomorrow!!!

Next Blogger is Brandon M.

The ANSWER!!!!

Guys, question 2 for the pre-lab questions is now available. Here:

STEP 1:
X+Y=150g
 Obviously, X=50, Y=100

This is the total amount of water you have available. You are mixing the water together.


------------------------------------
STEP 2:
X(20)+Y(70)=150(Z)

This is like the concentration and solution problems. You have a 20 celsius water and a 70 celsius water, so they are like different "concentrations" for the different amounts of water.
so just plug in the values and solve for Z.

-------------------------------------
STEP 3:
50(20)+100(70)=150Z
Z=53.33 Celsius.

Hopefully, you understand it. This is just a system of equations.

Heating Curves and Heat Calculations

Heat Curves and Calculations

A blog brought to you by: Grace Kilpatrick

Hi everyone! Today, February 13, 2014, we had yet another wonderful day of chemistry class. Here's what went down:

1) Mrs. Friedmann began class by wrapping up yesterday's notes titled "Heating Curves". These notes can be found in the Unit 8 Notes folder (titled 2.12_Notes_on_Energy_and_Heating_Curves.pdf) or at the above link . These are very important notes so be sure to check they are in your journal!

2) Mrs. Friedmann went over last night's homework titled "Phase Changes". These notes can be found in the Unit 8 Handouts folder (titled 2.12_Heating_Curve_and_Phase_Changes_Ws.pdf) or at the above link. Part C, Phase Change Calculations, proved to be a bit of a challenge. This is how to solve them:

-My keyboard lacks a delta key, so this will be indicated in equations by a "*" symbol.

29.
Step 1: Heat required to raise temperature -15.5 C to 0 C
q= m x c x *t
q=32.9 g x 2.03 J/g C x 15.5 C= 1040 J

Step 2: Heat required to convert 0 C ice to 0 C liquid
q= n x *Hfus
q=1.83 moles x 6.0 KJ/mole=11000J

TO FIND # of MOLES: USE MOLAR MASS CONVERSION

Step 3: Heat required to raise temperature 0 C to 32.9 C
q= m x c x *t
q=32.9 g x 4.18 J/g C x 32.9 C=4520 J

Sum of Steps 1-3: 1040 J + 11000 J + 4520 J= 16560 J

30. This problem is essentially a continuation of question 29,. Since we have already found the amount of heat required to change 32.9 g of water at -15.5 C to liquid water at 0 C, we now only need to find the amount of heat required to change the liquid water at 0 C to gaseous water at 125 C. 

Step 4: Heat required to raise temperature 0 C to 100 C
q=m x c x *t
q= 32.9 g x 4.18 J/g C x 100 C = 13800 J

Step 5: Heat required to convert 100 C water to 100 C gas
q= n x Hvap
q=1.83 moles x 40.7 KJ/mole =74500 J

Step 6: Heat required to convert 100 C gas to 125 C gas
q= m x c x *t
q= 32.9 g x 2.01 J/g C x (125 C-100 C)= 1700 J

Sum of Steps 1, 2, 4, 5, 6: 1040 J + 1100 J + 13800 J + 74500 J + 1700 J = 102.04 KJ

3) We spent the rest of the class period working on our homework which includes:

-8.2 Webassign due at 11:59 TONIGHT! 
-Specific Heat of a Metal Lab due TOMORROW!
-Heating Curve Calculations Worksheets (x3) due TOMORROW! (see link)
-Heating Curve Calculations Practice worksheet due TOMORROW!- This is not available in the handouts folder currently, so you will have to pick it up in class!

4) On behalf of the whole class, we wish Jordan a quick and speedy recovery. We miss you and we hope you get better soon!


If you have been absent or are simply confused, here is a video that might assist you in understanding this unit:

The next blogger will be Kevin Mihelic.

Heat Curves and Phase Changes

Thermodynamics

To start off class today Mrs. Friedmann told us what we needed to do for our lab write up that is due Friday.  Here's what you'll need to do:

1. Title
2. Purpose
3. Data
4. Post Lab Questions

              - Write out each question

   5. Conclusion

            -Claim

            -Evidence

            -Reasoning

After, she told us how to do the lab calculations.  For example, if the hot metal bar was 100 degrees Celsius, and the cool water was 23 degrees Celsius and we placed the metal bar in the water, the temperature of the water would decrease and the temperature of the water would increase until they both reached the same temperature.  The heat from the metal bat went into the water, therefore, the heat lost by metal is equal to the heat gained by water.  Using this, we can say that:

                      q=m*c*change in T = m*c*change in T=q

                                (metal)                 (water)

So that means the q metal= q water

That must mean...

                              m*c*change in T= m*c*change in T

                                      

                                      (metal)               (water)

Now all that's left to do is plug in your numbers and solve for c!

Specific Heat of Metal Lab

Our homework tonight is...

1.Webassign due tonight by 11:59 pm

2.The two worksheets on specific heat capacity 

3. Lab due Friday 

Hey guys! So today in class we did a lab. The purpose of the lab was to identify a sample of metal by  determining its specific heat capacity. 

We started class by answering the pre-lab questions...

1. ~50,000J.

2. You shouldn't eat snow to get water because your body will use energy to make that snow into "usable water" instead on using energy to heat your body. You'll basically freeze from the inside out. So don't eat snow :)

We then immediately started the lab. 

Procedure:

1. Fill a 600mL beaker half full with water and heat to boiling using a hot plate. 

2. Record the mass of the metal bar. CAREFULLY place the metal bar into the beaker. Don't let it sit at the bottom, suspend it above the bottom, still submerging it in the water. 

3. Prepare a calorimeter (styrofoam coffee cup) for use: place about 100mL of water in the calorimeter. Record the exact volume in a data table

4. Measure the initial temperature of the water in the calorimeter and record it in your data table

5. CAREFULLY take the metal bar out of the boiling beaker and place it into the calorimeter. Use a stirring rod to stir the water. Then record the highest final temperature the water reaches. 

Here is the data Pamela and I got...

Next Author: Mary L. 

Thermochemistry

Thermochemistry

Hey guys I'm so so sorry for getting this up so late but here we go...

Today in class we had a sub so it was a pretty laid back day.  We completed a reading sheet on the differences between heat and temperature, which the sub collected at the end of the period.  The main thing that you need to remember in order to differentiate between the two is that temperature is the measure of how fast a substance's atoms are moving, while heat is the energy released after the temperature change.  

This is a new concept, so if it seems confusing it's okay!  Make sure to save your questions for Mrs. Friedmann for when she gets back. 

Homework

1. Answer the pre-lab questions that we got in class (It doesn't look like this is posted in any of the folders yet, so if you missed you can pick up a copy tomorrow)
2. Webassign due Tuesday night at 11:59 pm
3. Watch Crash Course Energy and Chemistry (Link in Unit 8 box

Next Blogger: Georgia A.

Intermolecular Forces (Day 3)

2/6/14
Scribe Post: Juliette Ovadia

Agenda

First, Mrs. Friedmann checked in our homework. The homework was two worksheets, the Intermolecular Forces table and the eight questions on the Intermolecular forces worksheet. Next, we had a discussion about Solar Roadways which was brought up yesterday and other such innovations. We then went over the homework and Mrs. Friedmann answered our questions about the worksheets, web assigns, and review packet. We were supposed to also complete a lab, the Physical Properties of Liquids Lab, but we did not have time to complete it. 

Class Discussion

At the beginning of class, we watched a video about Solar Roadways. According to the website, "The Solar Roadway is a series of structurally-engineered solar panels that are driven upon. The idea is to replace all current petroleum-based asphalt roads, parking lots, and driveways with Solar Road Panels that collect energy to be used by our homes and businesses." 

More information can be found on this website: http://www.solarroadways.com/intro.shtml, and the video above is a short documentary about the innovation.

We also discussed the idea that it is the small solutions that make the greatest impact. For instance, in third-world and developing countries especially in Africa,  people have to trek for miles carrying heavy tanks to get water, and usually those making that trek are women. The Hippo Water Roller was invented as an easier, less taxing way of carrying water. The video above details the innovation.  

We also discussed solar power, and how we can innovate so that we are not so reliant on fossil fuels. Illinois uses a lot of nuclear energy, yet even nuclear energy comes with its own problems. There is a very interesting growing field called biophotovoltaics, which is working on artificial photosynthesis and how we can harness the power of the sun and plants for solar power. Specifically, a recent paper by Andreas Mershin and some researchers at MIT details how Photosystem I can be aggregated from discarded crops or timber, stabilized by some chemicals, and spread out on a "nanoforest" of semi-conducting electrodes of ZnO nanowires and TiO2 nanostructure that can produce an electric current when exposed to light. This could mean that in a few years people in third-world and developing countries could use discarded plants, a bag of chemicals and some written instructions and paint this/install this on their roof and have solar power. Right now the efficiency is only at 0.1-0.8% but the field is clearly advancing and such an innovation would be extremely useful and life-changing in developing countries. Click here for the link to the paper on this biophotovoltaics innovation 

Homework

We went over both of the worksheets in class today. Important things to remember about intermolecular forces:

• Nonpolar--> main IMF London Dispersion Forces even though LDF is at work in every molecule (symmetrical)

• Polar --> main IMF Dipole-Dipole (assymetrical)

• Usually, if polar w/out a hydrogen attracted to O, N, F (FON) --> dipole/dipole 

• If Nonpolar --> London Dispersion Forces

• Polar w/ H attracted to F, O, or N--> Hydrogen Bond

• In addition, these intermolecular forces are on a continuum. We learn the extremes, and the muddy area is for experimentation.  H Bond (strongest) <----------> London Dispersion Forces (weakest)

Key to Worksheet 8 Questions

We also discussed CH4O, methanol. The lewis structure is to the left. Remember, any molecule with an O-H bond is an alcohol (though not necessarily alcohol as in beer and wine). In CH4O, the main IMF is Hydrogen Bonding, which is stronger and better at sticking molecules together and therefore is the stronger/main IMF. Mrs. Friedmann also showed us the lewis structure for ethanol, which is what is in the beverage alcohol. The lewis structure for ethanol is above.  Ethanol also has an O-H bond so has H-bonding. Methanol is wood alcohol, a paint thinner that is dangerous to drink. During the Great Depression and Prohibition, alcoholics drank methanol as an alternative to beer and wine. The body metabolizes ethanol into ethaldihyde, however that same enzyme does the same chemical reaction to methanol and turns it into formaldihyde. Formaldihyde is dangerous because it freezes molecules into place and preserves them, essentially "pickling" the body. The "cure" is to drink a lot of alcohol. 

In addition, we discussed hydrocarbons. With an extremely long chain of hydrocarbons, even if there is an oxygen connected to a hydrogen, the main IMF would be London Dispersion Forces because of the great amount of hydrocarbons. The longer the non-polar side, the stronger the LDF and the increased viscosity.

Key to Worksheet w/ Table

On the second worksheet with the table, the answer to the motor oil question is as follows on the key:

Since motor oil is needed to quickly coat all surfaces of an engine to keep them from getting too hot, a low viscosity material is better than a high viscosity material. 

*Viscosity= measure of how well substances flow

*contains H-bond which means high velocity, motor oil has LDF only so it has low viscosity

We also went over sigma and pi bonds, that a pi bond is the last pair of electrons for example on the S in SO2 which spreads out and balances the structure. A pi bond is ultimately an area of space electrons can occupy, orbitals available. The key is that electrons don't stay stuck in between 2 atoms in a pi bond, if there is an empty pi bond they will smear onto it and occupy the entire space, and we show resonance to demonstrate this.

Had we done the lab, we would have worked with:

1) Hexane --> no polarity so main IMF is LDF and would evaporate quickly and have a low boiling point

Hexane

2) Vegetable Oil --> LDF and Dipole-dipole and polarity, but the predominant intermolecular force is LDF

3) Water --> Hydrogen bonding

Homework

Study for Unit 8 test tomorrow! 
A good way to study would be to work on the review packet. The key is posted on moodle. 

The next scribe post author is: Valerie Korol

Addendum to Kevin Gordon's 'IMF continued' post... February 5, 2014

First, a relevant chemistry joke... I actually just typed in 'chemistry joke' (and got a lot of good stuff), and came across this, and felt really smart that I now understand it!



Additonally... Kevin Mentioned a 'cazy' idea he heard of: turning all the roads and pavement into solar cells! Mrs. Friedmann responded by talking about a crazy idea she heard of... giant aluminum tubes that fly in the sky, with two giant metal wings on the side shaped to create upward life when air passes over and under it, charging people to sit in seats and go across the country in like 5 hours... crazy, I know.

Anyway, the thing Kevin talked about (All the literature spoke of the organization 'Solar Roadways', but there may be other initiatives) can be looked at here:
http://www.solarroadways.com/intro.shtml very interesting

---------------------------------------------------------

The thing I mentioned from Policy debate last year (me and nimil ran across a team using this affirmative) was Piezoelectric highways, and I admit, I did scoff at the idea (and I also had to argue against it, being a debate and all): http://www.innowattech.co.il/technology.aspx Energy parasites, very intriguing

---------------------------------------------------------

And furthermore, the moment Mrs. Friedmann began her little spiel about never thumbing your nose at something deemed 'crazy,' I was reminded of this poem (That I very much like and commend) by Edgar Guest, [first stanza]:

Can;t is the worst word that is written or spoken;
Doing more harm than slander and lies;
On it is many a strong spirit broken,
And with it many a good purpose dies.
It springs from the lips of the thoughtless each morning
And robs us of courage we need through the day:
It rings in our ears like a timely sent warning
And laughs when we falter and fall by the way... [and it goes on for three more stanzas; read it here http://allpoetry.com/poem/8471321-Cant-by-Edgar-Albert-Guest]

International Monetary Fund... (just kidding!)... IMF Continued

Homework for tomorrow, Thursday, February 6th:
-2 Inter-molecular force worksheets
- One web assign due 11:59pm Wednesday night

REMINDER: Test Friday

All About Inter-Molecular Forces (IMF)
weakest     1)London Dispersion Forces (LDF) (aka Vanderwahl's force)
stronger     2) Dipole Dipole interaction
Strongest   3)Hydrogen bonding (n.b. misnomer - they are not officially bonds...)

1) LDF's---Between Non-polar molecules - weak and short lived
-Induced dipoles in a nonpolar molecule (temporary, billionths of a second)
    - Although electrons are shared equally, they move constantly
    - Electrons can flow more in one direction than another, creating a temporary dipole
    - The larger/longer the nonpolar molecule, the larger the effect of LDFs, ie more viscous
e.g. Hydrocarbons---lots of bonds to create dipoles





2)Dipole-Dipole interactions - Between Polar Molecules - Stronger than LDFs
- Intrinsic (not induced)    
-Permanent (not temporary)
- The attraction between positive (+) dipoles and negative (-) dipoles




3) Hydrogen bonding - DIPOLES ON STEROIDS - Really small and weak (and therefore negative) hydrogen bonded to either Fluorine, Oxygen, or Nitrogen

e.g. water (bent shape, polar) - Large, electronegative oxygen atom holds the electrons very close, thus forming a very negative dipole, while the  hydrogen thus form very positive dipoles, attracting all the other extremely negative and positive dipoles of all the water around each other to 'stick' to each other - this stickiness is why water has such a high boiling point - 212 degrees Farenheit!

Sidenote: Bonds are giving and sharing electrons (ionic and covalent), while hydrogen 'bonding' is the attraction between negative and positive dipoles, so it is not really a 'bond'





NEXT SCRIBE, (Drumroll please), is Juliette