Monday, November 25, 2013

November 25, 2013

We turned in the Molar Volume Lab and checked in the homework first, and then went over said homework (Gas Stoichiometry 1). Then we took a partner quiz, which we initially thought was for a grade, but turned out to be mainly for practice at the end. The answers for it should be on Moodle.

Homework:

Study for test

Correct partner quiz

Also, charge your calculators

The next blogger is Elaine S.

11/22

review yesterday: When reaction occurs, the pressure changes to create equilibrium with the atmosphere.


Regular buildings don't affect atmospheric pressure.

We talked about laws of gases and changes in pressure that are regulated in certain buildings or underground caves and how pressure differences can be used to contain viruses in the CDC building.

Stoichiometry:

Volume of a gas under 2 sets of conditions, non-standard temperature and non standard pressure

Here are some examples, these problems can be found in the Unit 5 handouts folder, here’s how to set up the equations if you don’t understand it.

Ammonia is NH3, our “B” chemical, 6NO is our “A” chemical, however there is a typo in the question, there is no indication of pressure or temperature, so we assume STP and -273 degrees kelvin.

Start by writing 12 L NO, turn it into moles by using volume, 1 mol NO/ 22.4L NO.

12 L NO x(1 mol NO/22.4 L NO) x (4 mol NH3/6 mol NO) x (22.4 L NH3/1 mol NH3)

12 x 4 / 6 = 8 L NH3

102 g H2S x (1 mol/34.09 g H2S) x (3 mol O2/2 mol H2S) x (22.4 L O2/1 mol O2) =

100.5 ->101 L O2

12 g H2O2 x (1 mol H2O2 / 34.02 g H2O2) x (1 Mol O2 / 2mol H2O2) = 0.18 mol O2 -> PV=nRT

746 mmHg x V = 0.10 mol O2 x 62.4 (Lx mmHg/mol x K) x 300 K

V= 4.5 L

REMEMBER: You can treat volume like moles when its at standard pressure.

At the end of class today we did a demo about pressure how marshmallow and shaving cream expand in in volume when pressure is decreased and shrivel when pressure increases.

DONT FORGET TO DO YOUR PACKET THIS WEEKEND AND STUDY

Thursday, November 21

Class Blog 11/21/13

This morning we enjoyed a lecture from energy employee at Google, Arun Majumdar!

First we started off class by showed Mrs. Friedmann our homework, which was a two-part worksheet titled "Open and Closed Manometer Problems" (here)

Next we picked up 4 handouts

         -"Lab: Molar Volume" (2 sheets)

         -"Molar Volume of a Gas"

         -"Table 1. Vapor Pressure of Liquid Water Between 15 C and 29.9 C"

We didn’t have class time to review the homework, so we have to grade ourselves against the key on Moodle (here, scroll down) for homework.

For the rest of class we completed the Molar Volume Lab

Homework:

-2 Web Assigns due tonight at 11:59

-Print Unit 5 Review Packet

-Correct “Open/Closed Manometer Problems”

-Watch this video and take notes

-Lab Write Up

-All is due Friday 11/22/13 except for the lab write up, which is due Monday.

Next Blogger: Carrie R.

Today in class Mrs. Friedmann checked the gas variables packets and then went over the pressure handout.

Class Notes:

Kinetic Molecular Theory (KMT)

1) The behavior of gases depends on the movement of gas particles

2) Temperature is a measure of the average kinetic energy of the gas particles

Two big points:

·         All molecules in a gas do not move at the same speed (even if there is only one kind of molecule).

·         When a gas is a mixture of molecules, the differences in speed are even greater. Large molar mass is slow. Small molar mass is fast. But the average is the same.

3) Assumptions:

·        No attractions between molecules

·         Molecules are infinitely small

·         Particles are in constant motion

·         Pressure comes from collisions with container walls

·         Deviations from this “ideal” are largest at very low temperatures and very high pressures

·         At STP (0 degrees Celsius and 1.0 atm) ideal works

4) Things that increase pressure:

·         More molecules (more collisions)

·         Smaller volume (more collisions)

·         Higher temperature (more collisions and greater force of collisions)

Homework:

Complete “Open and Closed Manometer Problems” worksheet.

The next blogger is Frankie S.

Tuesday, November 19

Tuesday, November 19

What happened today?
There were three worksheets to pick up today, one titled Pressure and two titled Open and Closed Manometer Problems.
We checked in the Gas Problems worksheets that was last nights homework. Then went over them. The key should be posted on Moodle.
We got our Gas Variables packet back. The key for this is on Moodle as well.

Notes!

Flexible Containers

ex: balloon

• pressure stays constant
• volume changes

Inflexible Containers

ex: metal tank

• volume stays constant
• pressure changes

Direct
as one goes up, the other goes up.

Indirect
as one goes up , the other goes down







Demo!
Mrs. Friedmann put a whopping 15 balloons in a pretty small container of liquid nitrogen!
How? SCIENCE!
         











They came out like the balloon on the left but soon enough returned back its normal shape on the right side. The temperature from the liquid nitrogen slowed the gas molecules on the inside down and because the balloon is a flexible the pressure stays the same but the volume changes!

Homework!
Check your Gas Variables packet against key and make corrections in a different color.
Mrs. Friedmann WILL be checking!



Next scribe is BOBBY R.

Monday, November 18

First, we checked in the two Ideal Gas Law worksheets then, went over the answers.

Then, we took brief notes.

The Ideal Gas Law
PV=nRT
*P is Pressure
*V is Volume in Liters
*n is number of moles (if given grams convert to moles)
*R is Proportionality Constant
*T is temperature always convert to Kelvins

The Combined Gas Law
P1 times V1 divided by n1 times T1 equals P2 times V2 divided by n2 times T2  (sorry I don't know how to type it in looking normal...)
*This is used for the behavior of a gas when conditions change
*think of this as a "Before and After" problem

After this Mrs. Friedmann showed us a few demos:

• She demonstrated atmospheric pressure 
• Pressure is caused by atoms crashing in to things and with enough atoms it exerts a force
• In the demo with the flask full of water and a note card flipped upside down, the water did not spill out because of the atmospheric pressure on the note card was pushing the note card up on to the flask.
• She demonstrated how temperature changes pressure and volume. 
• The flask had boiling water in it and when the hard boiled egg was placed on the top of the flask it was being pushed off due to the high pressure coming out of the flask. 
• Once Mrs. Friedmann placed the flask into the ice water, the hard boiled egg was sucked into the flask because the cold temperature made the volume of the water vapor decrease. 
• Finally, she had Gemini get into a plastic garbage bag and she sucked the air out of it.  This demonstrated 14 psi on her. 

The homework is two pages of Gas Problems

Next Blogger... Francine!!!!

Class Blog 11-15-13

So sorry I failed to blog the past few days, but the days were quite uneventful. To compensate, I will also blog for today.

11-13-13

Took the test. Hope everyone did well!

11-14-13

We went over the test.
We also had a small demonstration of barely freezing a soft drink so that it becomes a slushy when it opens.

11-15-13

We received an assignment from the sub titled "Gas Variables". We spent the entire period filling out the worksheet. By the end of the period, we turned it in.

Homework is two worksheets with a number of problems on it. There is also a video on moodle about the ideal gas law and will help solve the problems on the homework. Please watch it and take notes for homework.

Class Blog 11-12-13

Class Blog 11-12-13

We started out by going over what will be on the test and what will not be on the test.  Next we went over colligative properties that we need to know.

Things not included in this unit:

-Molarity is not the only way to measure concentration!

-molality

-mass percent

-mole fraction

-volume percent

-parts per million (ppm)

-parts per billion (ppb)

-How to calculate the colligative effect of a solute in a solvent.

Colligative properties notes:

-Physical properties of solutions that depend on how many solute particles are present... not on what the solute is.

-Adding any kind of solute (mixing “pieces” in with a solvent) will change the way the solvent behaves.

Ones we need to know:

1. Boiling point goes up. (temp at which solvent boils).

2. Freezing point goes down. (temp at which solvent freezes).

3. Vapor pressure goes down.

4. Osmotic pressure goes up.

-The more pieces of solute in the solvent, the greater the effect on colligative properties.

  ex. C6H12O6 (s) ---> C6H12O6 (aq) 1 piece

NaCl (s) -------> Na+ (aq) + 2Cl- (aq) 2 pieces

CaCl2 (s) ------> Ca2+ (aq) + 2Cl- (aq) 3 pieces *Biggest Effect

CO2 (g) --------> CO2 (aq) 1 piece

Homework:

STUDY!!!

STUDY!!!

STUDY!!!

Reminders for Test:

-Study session for the test is at 7 am tomorrow (11-13-13)

-The video going over the study packet will be posted on moodle by 4 pm today.

-The stoichiometry precipitate worksheet is extra practice for the test (this was handed out last week)

Good Luck on the test everyone!!!

Next scribe is Dana S.

Class Friday, November 8, 2013

First we checked in the Molarity and Concentration and Solution Stoichiometry worksheets.  The keys can be found in the Unit 4 Handouts folder.

The test was moved to WEDNESDAY, instead of Tuesday.  There will be a 7 am study session in our classroom on Wednesday morning.

We then picked up 3 handouts:

1. Chemistry Scene Investigation- Trouble in the Chemistry Store Room lab

2. Precipitation RX Stoichiometry worksheet

*these are optional practice problems to prepare for test

key will be posted this week

3. Unit 4 review packet

*not due for points but best source of practice for test

video of corrections will be posted

HOMEWORK:

1. Read and take notes on 10.3 and 10.4 in textbook

*she will check in notes on Tuesday

both sections have calculations and textbook teaches calculations BUT: 

we do NOT have to know how to do calculations

know big ideas about colligative properties

biggest difference between molecular and ionic compounds is dissolving in water:

molecular- does not break apart

ionic- separates, breaks apart into pieces

2. Webisign on 10.3 based on reading

*emphasizes important topics

due Monday by 11:59 pm

no reading sheet with webisign

LAST NIGHT'S HOMEWORK:

*key is posted

We went over some of the problems in class.

purpose: distinguishes between molarity of ion and molarity of solution

QUESTION 2:

-molecular bonds cannot be broken in the water

so molecular compounds will NOT separate- not as big an effect

molecular bond is too strong for water to break apart

-ionic particles are weaker 

water molecules surround and push ionic compounds apart

basically just find moles of chemical and multiply by how many pieces of molecule

*use dimensional analysis- most powerful calculating technique

instead of solving for x

challenge yourself to use that tool

  QUESTION 3:

-do math

-then explain physical lab

*These calculations are for practical purposes and are commonly used by chem teachers to make solutions.

  pg. 2 QUESTION 1

-calculate total moles and total liters

find moles per each solution

add together

divide by total amount of liters (volume)

Mrs. Friedmann then did a super-saturated solution demonstration.

There was a pack with a lot of sodium acetate and not a lot of water. The way we got it to dissolve in the water is we heated it up and boiled it. We raised the temperature of it so the solubility of the salt went up because the temperature went up. Then we let it slowly slowly cool down. So there is a lot of extra sodium acetate (super-saturated) that is ready to come out. So when it does come out it will only come out until it is saturated. All of it will not come out of the solution. It will come out until the solution that is left is saturated.  

There was a metal disc in the pack. By flipping it back and forth you made the molecules rub against each other and create friction to excite them to the point where they start to crystallize out. As soon as some of them begin to crystallize out, it is a chain reaction and everything comes out of the solution at the same time.

After flipping the metal, a hard white matter began to spread throughout the pack and it became a hot pack.

We then went over part of the chem scene investigation lab but did not have time to actually do it.

-To solve we set up balanced reactions.

-Then look at solubility charts.

Next scribe is Connor H.