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.