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.

• First, we went over the Solution Stoich Worksheets.
• The key can be found in the Unit 4 Folder under Keys.

• Next, we got back our "Concentration and Molarity PhET-Chemistry Labs," and went over it.
• The key can be found in the Unit 4 Folder under Keys.

• Next we had a visit from our good friend The Fire Alarm, which took up some of our class time.

• Today's homework were two worksheets called Molarity Thinking Problems. 
• These can be found under the Unit 4 Folder under Handouts.

• Extra Information
• Our Unit 4 Test is NEXT TUESDAY!!!

• The Next Scribe is Grace Moran

11/6/2013

First, we had to turn in our Concentration and Molarity PhET Simulation Packets.

We received three sheets, each titled Solution Stoich, which we taped into our journals. These sheets should be available in Moodle under Unit 4 handouts.

We then began to take notes on solution stoichiometry, which should be available on Moodle under Unit 4 notes.

The homework was the three sheets we received earlier.

Next scribe is Danny S.

1) We started off the day by checking in the molarity packet and worksheets with Mrs. Friedmann.  

2) Later we checked the homework and asked questions. The key is posted on Moodle.

Class Notes:

Big Ideas About Molarity:

(Also posted on Moodle)

1) Molarity is MOLES solute and LITERS solution. (Not liters water)

2) If you are given grams solute then convert to moles.  If you are given mL solution then convert to liters

3) What if you are given GRAMS of solution? How do you convert to volume of solution? You would need density of solution.

Example:

g solution x mL solution/ g solution x 1 L solution/ 1000mL solution = L solution!

4) You should know how to mix up a solution of a particular molarity, at a specific volume.

How to Mix a Solution:

(Also posted on Moodle)

Suppose you work in a chemistry lab. Your boss tells you to make 0.50 liters of a 0.75 M solution of sodium chloride. How would you do it?

Calculations:

0.75 mols NaCl/ 1 L solution x 0.50 L solution = 0.38 mols NaCl needed

Procedure:

1) Measure 22g of NaCl, using a balance.

2) Put the NaCl into a 500 mL volumetric flask with less than 500mL water in it.

3) Swirl until all the NaCl is completely dissolved.

4) Fill the volumetric flask to the 500mL mark.

The next blogger is Andrew S.

Class Blog 11/4/13

Before Class:

1. First, our homework (Solubility Curve Practice Problems Worksheet) was checked in for points.

2. Next, we picked up three handouts. One was a packet titled “Molarity: How can the concentration of a solution be expressed quantitatively?” (can be found here), and a two part worksheet simply titled “Molarity” (can be found here)

During Class:

1. We started class by reviewing each question on the Web Assign which was due Sunday night at 11:59 PM. The Web Assign didn’t show us whether or not we got the answer wrong, so don’t freak out!

-Some main ideas to pull from the Web Assign: whenever a compound is insoluble, it will create a precipitate. The inverse is also true; if a compound is soluble, then a precipitate will not form.

-Our textbook has very helpful examples regarding the Web Assign questions.

-Also remember that it is more important to learn the big idea of a lesson even if it means losing a couple points here and there. Don’t get hung up by one bad grade!

2. Next we reviewed our homework that was due today (Solubility Curve Wksht)

-Answer key can be found here.

3. After this, we worked with partner on the Molarity packet up to the first stop sign.

-We ended class by going over the answers quickly

Homework:

1) Worksheets (2):  Molarity

-Due tomorrow in class

2) WebAssign 10.2 - Solubility.  Due tomorrow night by 11:59 pm.

3) Finish the Molarity Packet, and check against the key on Moodle.

-Due tomorrow in class

Next Scribe: Bobby R

Class Blog - November 1st, 2013

On the worksheet that was assigned for homework, you must write the net ionic equation as well as the molecular (completely balanced) equation. 

http://en.wikipedia.org/wiki/Solubility_table
(After a 10 minute discussion, we also successfully established that Wikipedia can be trusted mostly...) 

For a reaction to happen, one of the ions must be insoluble. 

• For the molecular equation, don't add charges.
• For the net ionic equation, add charges. 
• For the complete ionic equation, add charges.

-If you need help with the difference between net ionic equations and complete ionic equations, this site may help:
http://www.occc.edu/kmbailey/chem1115tutorials/Net_Ionic_Eqns.htm

We also discussed the solubility rules (which can be found on Solubility of Common Compounds homework worksheet. 

Sodium oxide reacts violently to form sodium hydroxide. This means that sodium oxide is not soluble. Potassium oxide also reacts to form potassium oxide.

We also got a graph of the solubility of sodium acetate. 

The process of making it soluble is very precarious because it must be a certain temperature and a certain saturation so that it will have enough water molecules to make it soluble.  

Next we went to the Solubility Curve Practice Problems worksheet (which we received before today). We noticed that

• The lines that were solid went up.
• The lines that were gases went down. 

HW:

-Solubility Curve Practice Problem Sheets

NEXT SCRIBE: Frankie Sulejmani